Femoral Acetabular Impingement and Labral Tears

Figure 4-1 Classifications of acetabular labral tears: radial flap, radial fibrillated, and peripheral longitudinal. (Adapted from Lage LA, Patel JV, Villar RN. The acetabular labral tear: an arthroscopic classification. Arthroscopy. 1996;12:269-272.)

The primary risk factors identified for acetabular labral tears are anatomic variants that affect hip joint function and type of physical activity. The association of age with symptomatic labral tears is debatable. Whereas the presence of labral tears does increase with age, the increased presence of hip OA must also be considered when attempting to determine a patient’s primary source of pain. Several connective tissue disorders that result in generalized joint hypermobility (Ehlers-Danlos, Down, and Marfan syndromes) are also associated with a higher risk of lesions of the acetabular labrum.

Patient Profile

Because of the nature of injury development, correctly identifying acetabular labral tears as a primary source of symptoms often takes a long time. The condition is often overlooked when the patient is given another diagnosis. The list of differential diagnoses for patients with nonarthritic hip pain is expansive and includes both musculoskeletal and nonmusculoskeletal conditions. Clinicians must carefully consider the patient’s history and complete clinical presentation to accurately determine the likelihood of an acetabular labral tear as the primary source of the patient’s symptoms.

As previously noted, most persons with symptomatic acetabular labral tears are relatively young and active. Even so, the reported age range for diagnosis of symptomatic labral tears is 8 to 75 years.3 Labral tears of the hip have been associated with a high proportion of athletes with complaints of hip pain.11 Athletic activities that have been associated with acetabular labral tears include running, ballet, golf, ice hockey, and soccer.12

Persons participating in these activities often maneuver their hips into the extreme limits of the available range of motion (ROM). In the presence of abnormal bony morphology, sport activities that require repetitive end-range positions may elicit intraarticular pain and symptoms, but they may also increase the risk of cartilage and labral injury.13 For this reason, clinicians should carefully inquire about a patient’s type of activity and correlation with symptoms during clinical evaluation. For clinicians to consider all potential diagnoses that may be applicable in a patient suspected of having a labral disorder, a comprehensive examination of the hip and pelvic complex should be performed. The reader is directed to review Chapter 2 for discussion of the hip examination process. Diagnostic imaging can help confirm the results of clinical examination. The later section on cam impingement discusses the use of imaging to diagnose acetabular labral tears and associated bony abnormalities.

Mechanisms of Injury

Although traumatic injury can occur, the more common mechanisms of injury tend to be the result of anatomic abnormalities that lead to mechanical overloading of the labrum over time. The tendency for damage to occur, when abnormal bony morphology is present, may be increased for those patients who participate in specific activities that increase the mechanical load placed on the hip joint. Heavy labor or athletic activities (as previously listed) may produce these types of forces. These activities are often repetitive. The most commonly described underlying anatomic mechanism of injury in the literature is FAI.14,15

Femoral Acetabular Impingement

FAI occurs when premature contact occurs between the proximal femur and the acetabular rim as a result of abnormal morphologic variations of the hip joint. Anatomic variants associated with FAI involve bony abnormalities of the femoral head and acetabulum. FAI tends to occur with specific movements of the hip joint. These movements typically involve flexion, internal rotation, or adduction. FAI is of particular concern in the younger, relatively active population.12 FAI may lead to acetabular labral tears and subsequent chondral damage in some patients.16 Although the specific etiology of FAI is not well understood, classification of the bony abnormalities related to FAI has been well described in the literature. The most common descriptions of FAI mechanisms include cam (femoral head and neck), pincer (acetabular), or mixed (cam and pincer) variations of impingement. Figure 4-2 illustrates the observed variations of FAI. The pathoanatomic features, common imaging findings, and distinguishing pathologic characteristics associated with FAI are discussed here.


Figure 4-2 Mechanisms of Femoral Acetabular Impingement. A, Normal clearance of the hip. B, Cam type. C, Pincer type. D, Mixed type. (Modified from Lavigne M, Parvizi J, Beck M, et al. Anterior femoroacetabular impingement: part I. Techniques of joint preserving surgery. Clin Orthop Relat Res. 2004;418:61-66.)

Cam Impingement

Cam impingement is the result of excessive bone in the region of the femoral head and neck junction. The processes responsible for this abnormality are not well understood. Investigators have suggested that cam deformities may result from processes or events that potentially disturb development of the bone such as slipped capital femoral epiphysis.17 When someone participates in repetitive activity requiring end ROMs (particularly flexion, internal rotation, or adduction), the femur makes premature contact into the acetabular rim and labral tissue.11 An example of a sport-specific activity requiring this ROM is a soccer kick. With repetitive exposure to these forces, the labrum often fails at the bony interface where it attaches into the acetabulum, and a tear results. As time passes, the labral tears may progress to chondral damage on the articulating surfaces of the femur or acetabulum. Cam deformities have been commonly associated with labral and chondral damage in the anterior superior region of the hip joint.9 Currently, a small body of evidence suggests that cam FAI is more prevalent in younger to middle-aged male patients.18,19 Investigators have suggested that participation in high-impact activity at a young age may contribute to the development of the CAM deformity in this population.13

Plain radiographic imaging is routinely used when attempting to confirm FAI as an anatomic factor that may play a role in a patient’s symptomatic presentation. Plain radiographs may also identify the presence of degenerative joint changes, which may be a differential diagnosis or prognostic factor in patients with FAI or tears of the acetabular labrum.20 Radiographs can help clinicians determine the specific impingement mechanism (cam, pincer, or mixed) and the magnitude of variation from normal values. Cam impingement can be identified by specific findings on plain radiographic imaging. These findings indicate an increased diameter of the femoral neck or excessive bony formation in the region of the femoral head-neck junction that results in a decreased head-neck offset.21

The alpha angle is useful in measuring femoral head-neck offset and examining sphericity of the femoral head. The alpha angle can be measured from examining anteroposterior (AP), cross-table lateral, or modified Dunn views.20,22 The alpha angle is measured by creating a circle around the peripheral borders of the femoral head. A reference line is then drawn from the center of the femoral head through the femoral neck. A second line is drawn from the center of the femoral head to the location where bone exists outside the circular border. The angle formed between the two lines is the alpha angle. The reported values for normal alpha angles vary, with the upper limits ranging from 50 to 60 degrees.22,23 Barton and colleagues24 determined the alpha angle to be 91% sensitive and 88% specific for identification of cam FAI when using a Dunn view. Figure 4-3 demonstrates an alpha angle value associated with cam impingement. Although not a technical measurement, the appearance of cam impingement on an AP radiograph is often identified as a “pistol grip deformity.” The nonspherical head blends with the femoral neck to give the appearance of a pistol handle.


Figure 4-3 Alpha Angle. A reference line is the drawn from the center of the femoral head through the femoral neck. A second line is drawn from the center of the femoral head to the location where bone exists outside the drawn circular border. The angle formed between the two lines is the alpha angle. An alpha angle of 73 degrees is associated with cam femoral acetabular impingement.

Currently, magnetic resonance arthrography (MRA) is the most common imaging modality used to identify acetabular labral tears and chondral damage.25 When FAI of the hip joint is identified, clinicians may wish to determine whether an acetabular labral tear has developed secondary to the condition. MRA imaging is the modality of choice in confirming acetabular labral tears. A gadolinium-based contrast agent is introduced into the joint by injection before imaging is performed. This approach has been suggested to allow better intraarticular visualization and more detailed imagery of the articular surfaces when compared with standard magnetic resonance imaging (MRI). Enseki and associates12 reviewed a number of studies that examined the sensitivity and specificity of MRA in identifying labral tears. The studies reviewed reported values of sensitivity ranging from 71% to 100%2629 and specificity ranging from 44% to 100%,27,29 when compared with arthroscopic visualization as the gold standard.

Although not routinely applied in examination of patients with suspected FAI or acetabular labral tears, other imaging options may be useful in determining the potential role of other pathologic conditions in the presentation of hip pain. Additional imaging options include MRI, computed tomography (CT), diagnostic ultrasound, and bone scan. CT technology provides the ability to create three-dimensional imaging of the hip that provides further information on joint architecture.12 This modality may prove useful in presurgical planning for complicated cases because it allows the surgeon to visualize the size and location of all possible impingement sources. This modality does not provide information on the acetabular labrum. The inclusion of three-dimensional CT imaging allows the surgeon to define more clearly the amount of bone to remove in each location; this is more difficult to determine during arthroscopic techniques. The use of an arthroscopic surgical approach allows only limited or intermittent visualization of the bony contour during the procedure. The high level of radiation exposure with CT imaging typically limits the application to complicated cases.30

Pincer Impingement

Pincer impingement is an innominate bone abnormality that is characterized by excessive coverage of the acetabulum over the femoral head. Several variations of increased acetabular overhang that may create pincer impingement have been described. The presence of an excessively deep acetabular fossa creates a condition of general overcoverage (coxa profunda). Coxa profunda has been debated as an underlying mechanism for pincer FAI, with no definitive agreement on the presence or strength of the relationship.31,32 Another condition that results in general overcoverage of the femoral head is acetabular protrusio (protrusio acetabuli, acetabular protrusion). Acetabular protrusio occurs when the femoral head is abnormally located toward the midline of the body secondary to medial displacement of the acetabular wall. In comparison with coxa profunda and acetabular protrusion, a retroverted acetabulum may result in focal anterior overcoverage of the femoral head. Coxa profunda, acetabular protrusion, and acetabular retroversion may occur in combination with each other. The osseous characteristics associated with pincer impingement have been reported to be more prevalent in female patients.33 The relationship of pincer FAI and chondral damage has not been as strongly established when compared with the relationship of cam FAI and cartilage injuries.34

Plain radiograph imaging is useful for identifying osseous abnormalities associated with pincer FAI. Measurements that can be used to identify the presence of general acetabular overcoverage include the lateral center edge angle (LCEA) and the Tönnis angle (also reported at the acetabular index). The LCEA and the Tönnis angle are measured on AP radiographs of the pelvis with the hip positioned in 20 degrees of hip internal rotation.20 The LCEA and Tönnis angle are radiographic indices that are routinely used to examine characteristics of the acetabular roof and the amount of coverage provided by the femoral head.20 The LCEA is a measurement of the amount of coverage afforded to the femoral head by the acetabulum. This angle is measured on an AP radiograph by drawing a vertical line down through the center of the femoral head and a second line from the center of the femoral head to the edge of the acetabulum (Fig. 4-4).20 Normal LCEA values vary by reference, but typically they are listed between 25 and 40 degrees. A measurement greater than 40 degrees is considered excessive and is associated with coxa profunda. In a study of 55 patients undergoing surgical treatment for FAI, Kutty and colleagues35 found 81% sensitivity and 100% specificity values for using the 40-degree threshold to determine acetabular overcoverage and pincer FAI. The ratio of the femoral head not covered by the acetabulum is termed the Tönnis angle.36 This measurement is used to assess the acetabular roof in the coronal plane.20 A normal Tönnis angle is between 0 and 10 degrees. A Tönnis angle less than 0 degrees is associated with pincer FAI.37 The literature evaluating the reliability of the Tönnis angle when used to diagnose FAI is scant.


Figure 4-4 Lateral Center Edge Angle (LCEA). The LCEA is measured on an anteroposterior radiograph by drawing a vertical line down through the center of the femoral head and a second line from the center of the femoral head to the edge of the acetabulum. An LCEA of 33 degrees is considered normal.

Focal anterior superior overcoverage associated with acetabular retroversion can be identified on plain radiographs by the presence of a crossover sign.38 The crossover sign is assessed using an AP radiograph. The position of the anterior and posterior walls is evaluated. If the acetabulum is positioned normally, the line formed by the anterior wall remains medial to the line formed by the posterior wall. When the acetabulum is in a retroverted position, the lines representing the anterior and posterior walls cross to form an “X” pattern. Figure 4-5 displays normal acetabular position and retroversion as indicated by a crossover sign. The validity and reliability of the crossover sign in diagnosing pincer FAI have not been agreed on in the literature. In a study of 43 pelvis samples from cadavers, Jamali and associates39 found the crossover sign to be 96% sensitive and 95% specific in determining pincer FAI. Conversely, Zaltz and colleagues40 found that 19 of 38 subjects identified with a crossover sign on plain radiographs did not have overcoverage of the acetabulum when examined with CT scanning.


Figure 4-5 Normal acetabular position (right) compared with a retroverted position (left) as indicated by a crossover sign. (From Henak CR, Carruth ED, Anderson AE, et al. Finite element predictions of cartilage contact mechanics in hips with retroverted acetabula. Osteoarthritis Cartilage. 2013;21(10):1522-1529.)

As with the case of cam FAI, other modalities such as MRI, CT, diagnostic ultrasound, and bone scan may be used on selected occasions. The applications of such modalities follow the same logic as with cam FAI cases. These imaging methods are reserved for when atypical information is required or for presurgical planning for difficult cases.

Mixed Impingement

Although FAI is commonly described as resulting from a cam or pincer deformity, most patients diagnosed with FAI have a combination of both forms of morphology. This is referred to as mixed pincer and cam impingement.41 Beck and associates9 reported that 86% of patients with FAI present with a combination of both forms of impingement, with only 14% presenting with pure cam or pincer impingement. The literature examining the reliability of specific radiographic measurements and mixed-type FAI is minimal.

It is important for clinicians to remember that symptomatic FAI is the product of both anatomic variations and patient-specific activity patterns. Patients with FAI characteristics who do not participate in activities requiring significant ROM in specific planes or who do not participate in repetitive activity may not become symptomatic.42 Although radiographic evidence of FAI is a useful tool in diagnosis and treatment, other sources of pain in the hip region must be considered and appropriately included or eliminated through the process of structured, thorough clinical evaluation of the patient. Table 4-1 summarizes the radiograph findings associated with FAI.


Radiograph Findings Associated With Femoral Acetabular Impingement

FAI Variation: Pistol Grip Deformity Alpha Angle Lateral Center Edge Angle Crossover Sign
Cam Present >50-60 degrees Normal Normal
Pincer Normal Normal >40 degrees (coxa profunda) Present (acetabular retroversion)
Mixed Present Present Variable Variable

FAI, Femoral acetabular impingement.

Joint Hypermobility and Instability

Joint hypermobility of the hip has been described as a risk factor for musculoskeletal pain, especially at regions that tend to be exposed to higher mechanical forces (anterior capsule and labrum).43 Generalized capsular hyperlaxity and focal hypermobility have been associated with the development of acetabular labral tears.43,44 Global ligamentous hyperlaxity associated with connective tissue disorders, such as Ehlers-Danlos disease, Down syndrome, and Marfan syndrome, has also been described as a significant risk factor for the development of acetabular labral tears.45 The Beighton score has been described as a method of identifying joint global hyperlaxity in patients (see Chapter 2).

Focal hypermobility of the hip joint most commonly manifests as anterior capsular hyperlaxity associated with repetitive and forceful activities that place the hip joint at end-range hip external rotation or extension, thus possibly compromising the integrity of the capsular tissue in this region, as well as creating attenuation of the iliofemoral ligament.12 If the iliofemoral ligament’s ability to restrict excessive motion is compromised, the labrum may be exposed to increased stress that raises the risk of structural failure and injury.46 Athletes such as dancers and gymnasts who participate in activities requiring repetitive and forceful hip and pelvic rotation have been noted to develop focal anterior laxity.43,47 This topic is further discussed in Chapter 8.

Several bony abnormalities occurring at the hip joint may contribute to instability or hypermobility. Insufficient coverage of the femoral head by the acetabulum or excessive inclination of the acetabulum has been described as potentially affecting the stability of the hip joint. Various imaging studies may be used in determining the possible contribution of osseous anatomy to symptoms in patients with hip pain secondary to joint hypermobility.

Plain film radiographs are commonly implemented early during the evaluation process for patients with hip pain, to aid in the differential diagnosis and identify the presence of pathologic bony anatomy features associated with instability of the joint. The previously described LCEA and Tönnis angle measurements are useful in identifying the insufficient coverage of the femoral head that is often associated with hip joint dysplasia. Hips with LCEA measurements less than 25 degrees are considered to be dysplastic.26 Hips with a Tönnis angle greater than 10 degrees are considered to be at risk for structural instability.26,36 Patients with acquired focal hypermobility of the hip joint may have no associated bony abnormalities, and therefore plain radiographic imaging findings may be normal for these patients.

Cartilage Lesions of the Hip Joint

The degree and specific pattern of cartilage damage associated with FAI or hypermobility and acetabular labral tears may be of clinical interest, particularly when considering the prognosis of patients with these disorders. Beck and colleagues9 studied 302 hips to determine whether specific anatomic variations affected the pattern of labral damage and cartilage degeneration. These investigators noted distinct differences in cartilage wear patterns when comparing the conditions of cam and pincer impingement. They observed that cam impingement was associated with focal anterior superior chondral damage that occurred as a result of separation of the cartilage from the labrum in a shearing manner. In contrast, pincer impingement was associated with more circumferential cartilage damage around the acetabulum. These investigators concluded that with pincer impingement, the labrum is crushed between the femoral neck and the acetabular rim, often leading to ossification of the labrum. Isolated cam or pincer FAI was not commonly observed in isolation. The most common presentation was a mixed type of both entities. These variations of acetabular labrum lesions were suggested to result in different patterns of cartilage damage.


The acetabular labrum plays a significant role in normal hip function. Injury to the acetabular labrum has been associated with pain and dysfunction. Numerous factors may lead to the development of labral compromise. Variations in bony anatomy may lead to FAI or joint instability. Labral tears have been associated with chondral damage. Cam and pincer FAI create distinct patterns of cartilage lesions. Identifying acetabular labral tears and associated conditions can be a challenging process. Successful diagnosis depends on an understanding of hip joint anatomy and structured clinical examination, and it may be assisted with the use of imaging modalities.

Differential Diagnosis of Related Conditions

The clinical evaluation of patients with suspected nonarthritic hip and groin pain is challenging because of numerous competing differential diagnoses that often produce overlapping symptom presentations.45,48 Although a common clinical priority is differentiating among the various causes (musculoskeletal and nonmusculoskeletal) of hip pain, clinicians should consider the coexistence of multiple conditions in conjunction with a intraarticular disorder that may require specific intervention considerations to maximize the patient’s rehabilitation potential. Several conditions examined in the literature may produce similar symptoms or complicate the presentation of patients with acetabular labral tears. Conditions that occur adjacent to the hip joint may refer pain or other symptoms to this region. Lumbar radiculopathy, pelvic floor dysfunction, and peripheral nerve entrapment should be considered or ruled out during the process of evaluating a patient with the presentation of localized hip joint involvement and other suspicious symptoms. The reader is encouraged to review Chapter 2.

The association of FAI with the clinical syndrome of athletic pubalgia has been described in the literature. Athletic pubalgia or sports hernia is an overuse syndrome that has been observed to be more prevalent in patients with FAI. Controversy remains regarding the specific anatomic structure responsible for pain and symptoms experienced in this population. However, it is generally accepted that the spectrum of athletic pubalgia injuries are the result of compromise of the musculature and or fascial attachments to the anterior pubis that leads to weakening of the abdominal or posterior inguinal wall.49 Hammoud and associates50 examined 38 consecutive professional athletes for an association of FAI and athletic pubalgia in a retrospective case series. These investigators found that 32% of the athletes who underwent arthroscopy to address FAI had undergone surgical procedures to address athletic pubalgia in the past. Additionally, 39% of patients reported relief of athletic pubalgia symptoms with surgical procedures to address FAI alone.

FAI has been associated with decreased hip and pelvic ROM.51,52 The limited ROM associated with FAI may contribute to soft tissue injuries of the hip resulting from the increased strain experienced by these structures during repetitive physical activities.50 Investigators have suggested that decreased hip ROM predisposes athletes to injury secondary to the resulting compensatory pelvic motion or trunk hyperextension during sport-specific movements.53,54 Birmingham and colleagues55 examined the effects of simulated cam FAI on pubic symphysis movement in cadaver hips. Transverse plane ROM was measured at the pubic symphysis. The investigators noted a significant increase in internal rotation motion at the pubic symphysis in the cam FAI group. The clinical diagnosis of athletic pubalgia is a process of exclusion. The reader is encouraged to review Chapter 5.

An emerging body of literature has identified extraarticular causes of hip impingement that are associated with patients who have poor outcomes after intraarticular surgical procedures. The types of extraarticular causes of impingement may include central iliopsoas impingement, subspine impingement, and ischiofemoral impingement. Central iliopsoas impingement is a source of anterior hip pain and has been linked to acetabular labral tears. This type of impingement causes a distinct pattern of anterior labral damage that does not extend into the anterosuperior portion of the labrum (e.g., 1- to 2-o’clock position). The damage often occurs directly adjacent to the iliopsoas tendon at the 2- to 3-o’clock position of the anterior labrum, is often confirmed via MRA, and is often treated with a surgical release of the tendon.55a It has been postulated that the impingement may be caused by one of two mechanisms: (1) a repetitive traction injury by the iliopsoas tendon that is scarred on adherence to the capsule-labrum complex of the hip or (2) a tight or inflamed iliopsoas tendon that causes impingement during hip extension.56 Subspine impingement is caused by a prominent anterior inferior iliac spine (AIIS) abnormally contacting the distal femoral neck during hip flexion.57 This may be caused by excessive muscular activity of the rectus femoris during repetitive knee flexion with hip extension, resulting in an avulsion injury of the AIIS. This repetitive traction injury is common in running sports and in sports such as soccer that involve rapid high-energy kicking.57 Upon healing, this often results in an enlarged bony protrusion at the AIIS that abnormally abuts the femoral neck during movements into hip flexion.56 Subspine impingement has been related to CAM-type FAI and may be corrected surgically.56 Ischiofemoral impingement is characterized by a narrowed space between the ischial tuberosity and the lesser trochanter, resulting in repetitive pinching of the quadratus femoris muscle.5757b The impingement has been reported to be mainly congenital but may also be acquired from a hip fracture or superior medial migration of the hip joint as seen with OA.56 Other forms of atypical hip impingement include greater trochanteric/pelvic impingement, abnormal femoral antetorsion, abnormal pelvic and acetabular tilt, and extreme hip motions.5657

The presence of radicular symptoms originating from lumbar or sacral regions may make the evaluation and treatment of patients with FAI and acetabular labral tears more difficult. Referred pain from the lower lumbar or sacral nerve roots typically causes symptoms in the gluteal region or posterior thigh. Fortunately, the referral patterns extend distal to the gluteal and posterior thigh as well, thus enabling the clinician to recognize the radicular presentation. Upper lumbar nerve roots may produce anterior thigh and groin pain and should be assessed through appropriate neurologic screening tests during the clinical examination.58 A complete discussion of nerve root patterns may be found in Chapter 10. Pudendal neuropathy is typically produced from compression and may manifest as groin pain and parasthesia.58 Pudendal neurapraxia has been reported in patients undergoing hip arthroscopy.58a Postoperative pudendal neurapraxia is typically a transient event.10 Obturator nerve entrapment may also produce exertional groin pain and adductor muscle weakness. Obturator nerve entrapment has been associated with significant adductor muscular development in athletes. Bradshaw and associates58b conducted a case series investigation that described 32 cases of athletes presenting with exercise-induced medial thigh pain secondary to fascial entrapment of the obturator nerve. Lateral femoral cutaneous nerve involvement (meralgia paresthetica) is generally not challenging to differentiate from a mechanical hip disorder. Symptoms are sensory related (anterior and lateral thigh), with no motor changes. The surgical procedure during hip arthroscopy or hip replacement by the anterior approach may contribute to the development of this condition. In a review of the literature, Cheatham and colleagues59 discussed other orthopedic surgical procedures involving the hip, spine, or pelvis as potential causes of iatrogenic meralgia paresthetica. When evaluating patients who present with nonmechanical signs or symptoms or vague clinical examination results, neurologic influences should be considered. This rationale should be employed in both conservative treatment and postoperative settings.

Clinical Examination

A detailed and structured approach to clinical examination is imperative in implicating acetabular labral tears and associated conditions as the primary cause of a patient’s symptoms occurring in the hip region. The reader is directed to Chapter 2 for a comprehensive description of this approach. An outline describing the approach for clinical evaluation of patients from the labral tear and FAI population, as described in this section, is contained in Box 4-1.


Box 4-1

Clinical Examination Approach for Patients With Suspected Acetabular Labral Tears or Associated Conditions

History (Through Self-Report Questionnaire and Interview)

Demographics: age, gender, living situation, and so forth




Symptom description or chief complaint




Burning or shooting

Locking or catching


Subjective feeling of instability

Symptom location

Anterior or groin*

Medial thigh or adductor region

Lateral thigh or greater trochanter region*

Buttock or gluteal region

Functional limitations

Activities of daily living

Labor- or sport-specific

Prior injury

Hip or other lower extremity joints

Nature of previous injury and description of symptoms

Previous treatment and reported effectiveness

Previous low back injury

Previous surgical procedure

Childhood disorders

Legg-Calvé-Perthes disease

Slipped capital epiphysis

Congenital dysplasia

Other significant past medical history

Physical Examination: Observation and Inspection

Static observation

Lower extremity alignment

Knee (valgus, varus, patellar position), foot position

Lumbar spine (increased or decreased lordosis)

Indicators of leg-length discrepancy

Pelvic landmarks: palpate ASIS, PSIS, iliac crests

Muscle atrophy

Gait observation

Selective Tissue Tension Testing

Range of motion testing




General muscle groups of hip and pelvis

Specific muscles

Palpation of Anatomic Landmarks

Anterior region: ASIS, femoral triangle and contents

Lateral region: greater trochanter, bursae and proximal iliotibial band region, gluteus medius muscle belly

Posterior region: PSIS, ischial tuberosity, sciatic nerve


Thomas test/modified Thomas test

Ober test

Hamstring length

Adductor group

Clinical Tests

FABER test

Impingement test (FADIR)

Log roll test (anterior laxity)

Resisted straight leg raise test

Scour test

Craig test (femoral anteversion)

Accessory Motion and Joint Mobility Testing

Joint distraction assessment

Determination of Leg-Length Discrepancy

Weight bearing

Non–weight bearing

ASIS, Anterior inferior iliac spine; FABER, flexion abduction external rotation; FADIR, flexion adduction internal rotation; PSIS, posterior inferior iliac spine.

*Presence of “C-sign”?

Demographics and Patient Interview

Basic demographic information helps clinicians determine whether a patient falls into the typical age range for acetabular labral tear and FAI. As previously mentioned, these conditions typically occur in the younger population. In relatively older individuals, OA of the hip may become a more likely primary diagnosis. Persons older than 50 years of age with hip pain of gradual onset have a higher likelihood of hip OA.60

Although traumatic injury is a possible cause of acetabular labral tears, most often the onset is gradual, and the tears result from an associated underlying condition (FAI or hypermobility).12 When injury is traumatic, it is often associated with a mechanism of sudden twisting or pivoting.45 Hyperflexion or forced squatting positions have also been associated with labral injury.61 Persons who participate in activities that require repetitive movements into positions of end-range extension, flexion, or internal rotation that potentially create impingement or excessive stress on the passive stabilizers of the hip joint may be at higher risk to develop acetabular labral tears. Specific sporting activities that have been associated with the development of acetabular labral tears include golf, soccer, ice hockey, running, and dancing.62,63

The patient’s description of symptoms may be beneficial when attempting to determine whether an acetabular tear is the primary cause of a patient’s hip pain. Pain is the most common complaint and may be described as sharp or aching.37 The primary location of pain is typically the groin region, but pain may also occur in the lateral thigh region.46,64 The presence of deep pain in a distribution that the patient can demonstrate by cupping the hand above the greater trochanter is often reported as the “C-sign” (Fig. 4-6), indicative of potential intraarticular pain.65 This should not be confused with superficial palpable pain that is often noted with tensor fasciae latae tendinitis, proximal iliotibial band (ITB) irritation, or trochanteric bursitis. Mechanical symptoms such as clicking, popping, or catching may be noted with acetabular tears.29,66 However, extraarticular conditions such as a snapping iliopsoas tendon or ITB may also cause audible symptoms67 (see Chapter 3).


Figure 4-6 C-Sign of the Hip. The hand is cupped around the anterolateral region of the thigh.

Symptoms that occur in atypical locations or are described with a quality different from pain should cue the clinician to consider alternate or significant concurrent conditions. The complaint of stiffness, particularly when occurring in the morning, is often associated with hip OA.60 Reports of paresthesia, burning, or radiating pain may indicate peripheral nerve involvement or involvement of the lumbosacral spine complex (e.g., meralgia paresthetica). Pain may also occur at the tendinous insertions of the pelvis (anterior superior iliac spine, posterior superior iliac spine, ischial tuberosity). Gluteal region pain may indicate lumbar or sacral spine involvement. Pain in adjacent regions, such as the knee and lumbopelvic areas, should be noted because these areas may be involved as part of the cause or result of underlying injury mechanisms.68

Physical Examination

Basic principles of structured musculoskeletal examination should be followed when evaluating a patient with symptoms that are expected to originate from involvement of the acetabular labrum and associated hip disorders.45 Assessment of lower extremity alignment, posture, gait, active range of motion (AROM) and passive range of motion (PROM), flexibility, strength, and joint mobility helps the clinician determine the contribution of various structures in proximity to the hip joint.

Posture Assessment

Static and postural observation may yield findings that predispose a patient with FAI to become symptomatic. An exaggerated valgus position of the knee may predispose the hip to move into excessive adduction and internal rotation with weight-bearing activities. This motion may contribute to the symptomatic presentation of patients with FAI.69 Austin and associates69 described controlling excessive hip adduction and internal rotation as an effective method to decrease symptoms of a patient with FAI. Pelvic position in the sagittal plane and the associated lumbar spine position should be noted. Of particular concern are exaggerated anterior pelvic tilt and concurrent increased lumbar lordosis. Ross and colleagues70 found that dynamic anterior pelvic tilt results in an earlier occurrence of FAI through movement of the hip in flexion and internal rotation. If this postural tendency is noted, further investigation to determine the underlying causes and whether they are treatable is warranted.

Gait Observation

Although no specific gait pattern is associated with FAI or acetabular labral tears, gait examination can be used to determine the effect of impairments on function.20 If gait deviations are noted, further examination should be performed to determine responsible impairments. Lewis and Sahrmann71 observed that patients who ambulate with anterior hip pain often tend to ambulate with a swayback posture (posterior displacement of upper torso and anterior displacement of the pelvis) and symptomatically improve when posture is corrected to a more normal position. These investigators examined 15 healthy persons walking with 3 postural variations (normal, swayback, and forward flexed). Those persons walking with a swayback posture demonstrated higher peak hip extension angles, hip flexor moments, and hip flexion angular impulse when compared with subjects walking with a normal posture.71 Tendencies of the pelvis to drop excessively into adduction or internal rotation in stance phase should be recognized. As previously mentioned, this pattern of movement has been associated with symptomatic FAI.69 Decreased peak angles of adduction, extension, and internal rotation have been reported in patients with symptomatic FAI.72 The clinician should note any abnormalities with gait such as an abductor-deficient pattern, asymmetrical step lengths, or excessive foot internal or external rotation during limb advancement.73 Additionally, the occurrence of abnormal or excessive movements at the lumbopelvic complex to compensate for insufficient or painful hip motion should be noted.

Functional Testing

In addition to gait, the clinician should observe the patient during performance of basic functional movements and assess the presence of pain or compensatory movement patterns. The use of total body functional movement assessment is recommended to assist in the identification of regional impairments local to and distal to the symptomatic region that may be contributing to symptoms.74An example of one such tool is the Selective Functional Movement Assessment. Whether a formal functional movement assessment tool is used or not, important information can be gained from assessing movements such as gait, sit to stands or squats, and step-downs. These basic movement patterns can be assessed in any clinic setting with minimal equipment and can provide additional information to the basic orthopedic examination. Sit to stand and squatting are basic activities of daily living (ADLs) repeated often throughout the day. This movement pattern should be assessed to identify any pain provocation or deviations, because a typical sit to stand transfer requires approximately 105 degrees of hip flexion.75 Figure 4-7 demonstrates weakness of the hip abductors and external rotators resulting in valgus collapse of the lower extremity during a “step-down” maneuver.


Figure 4-7 The patient demonstrates valgus collapse (excessive hip adduction and internal rotation) during a “step-down” maneuver, indicating weak hip abductors and external rotators.

Range-of-Motion Testing

Selective tissue tension testing should be used to differentiate deficits in PROM, AROM, and muscle strength. When assessing PROM, the quality of end feel should be examined to determine any observed limitations that are caused by insufficient muscle length, capsular restriction, or bony block or derangement. A marked loss of internal rotation (<15 degrees), particularly in the relatively older population, may indicate the presence of degenerative changes within the hip joint.76 When AROM values are markedly less than PROM values, a strength deficit should be suspected. The results of selective tissue tension testing may be particularly useful in guiding treatment.

Strength Assessment

Strength assessment in all planes of motion should be included in the standard examination of any patient whose symptoms may be secondary to an acetabular labral tear or associated condition of the hip joint. Although evaluation in all planes of movement should be performed, clinicians should note that specific patterns of weakness have been described in patients with nonarthritic pain.77,78 Harris-Hayes and associates77 compared hip muscle strength differences in 35 younger adults (18 to 40 years old) with chronic hip joint pain against 35 asymptomatic matched controls. The controls were matched by sex, age within 5 years, body mass index, and limb side. Diagnoses of the test group included cam FAI, pincer FAI, structural instability, and hip pain without notable radiographic findings for bony abnormalities. The investigators found that when compared with controls, the patients with chronic hip pain did exhibit weakness of the hip abductor and external rotator muscles groups. Furthermore, a trend of weakness of the uninvolved hip for the group with chronic hip pain was also identified. Casartelli and colleagues79 found that patients (n = 15) with symptomatic FAI produced less peak hip flexor torque when compared with healthy controls (n = 15). This finding was consistent in both isometric and isokinetic conditions. However, when analyzing electromyography (EMG) data, the investigators found that fatigability of the hip flexor muscle groups was not more pronounced when compared with controls. Weakness of hip adductors in patients with FAI has also been described.78

Lumbopelvic strength should also be considered during the evaluation process of patients with suspected acetabular labral tears. Although many differences exist in functional anatomy and pathologic process, an analogy can be made to the well-established concept of proximal stabilization that is often employed when evaluating patients with suspected pathologic conditions of the shoulder joint complex. Much like the scapular complex, the lumbopelvic complex must maintain appropriate stabilization to provide a solid foundation for use of the peripheral joints. The lower abdominal muscles may be of particular interest because of their role in controlling dynamic anterior pelvic tilt. As previously mentioned, the presence of dynamic anterior pelvic tilt has been correlated with FAI occurring earlier in the motions of flexion and internal rotation.70 Deficient lumbopelvic control may contribute to the development of lumbopelvic instability and sacroiliac joint disorders, which are commonly observed in conjunction with FAI and labral tears.

Muscle Length Assessment

A flexibility assessment of the hip and pelvic musculature should be performed to identify any muscle length impairments that may be contributing to abnormal movement patterns that increase the risk of symptoms in patients with labral tears of the hip. A differential diagnosis to consider when evaluating patients suspected of having intraarticular hip dysfunctions is the involvement of hip and pelvic musculotendinous structures.12,45 The iliopsoas muscle complex should be of particular interest. Damage to the labrum caused by excessive iliopsoas friction and even cases of iliopsoas impingement have been described in the literature.80 Internal coxa saltans (snapping hip) may be caused by snapping of the iliopsoas tendon across the anterior femoral head or joint capsule.81 The Thomas test can be used to evaluate flexibility of the iliopsoas complex and ITB complex.20 Lateral hip pain is often associated with trochanteric bursitis or proximal ITB inflammation. The Ober test can also be used to evaluate flexibility of the ITB complex.20

Joint Mobility Testing

Joint mobility testing may be useful in determining whether capsular mobility deficits are present in patients with acetabular labral tears. This determination may be particularly useful in patients with symptoms related to FAI. As discussed, FAI may be part of the degenerative process eventually leading to OA of the hip joint.6,82 The benefits of joint mobilization have been reported in patients with hip OA.83 Decreased joint mobility or pain relief with accessory motion testing is often considered an indication for the use of joint mobilization techniques. Because of the variable but relatively small amount of translational movement that occurs at the hip joint,84 joint mobility may best be assessed through long-axis distraction. Given that current clinical practice guidelines recommend manual therapy as a potential intervention option for patients with nonarthritic hip pain, joint mobility testing should be considered as part of clinicians’ examination methodology.12

Clinical Tests

Certain clinical tests have been described as useful in diagnosing acetabular tears or the underlying conditions associated with tears. Clinicians should have an understanding of which clinical tests are supported by the evidence in patients with nonarthritic hip pain. If a patient is younger, is involved in cutting or pivoting sports, and is found to have positive findings on a cluster of the following tests, the clinician should suspect the presence of an acetabular labral tear or an intraarticular disorder.45

Flexion Abduction External Rotation Test

The flexion abduction external rotation (FABER), or Patrick test, is intended to indicate the irritability of the hip joint in relation to passive movement (Fig. 4-8). The test can also serve as a general indicator of hip joint mobility. The FABER test may elicit pain in various regions (anterior, lateral, and posterior), and it may symptomatically implicate structures other than the hip joint, such as the sacroiliac joint when the test causes symptoms in the sacroiliac joint region.


Figure 4-8 The patient is placed in the flexion abduction external rotation (FABER) test position. Groin pain is associated with a potential hip joint disorder.


The patient assumes the supine position. The heel of the patient’s test extremity is placed above the opposite knee, thus allowing that hip to be in a flexed, abducted, and externally rotated position. The pelvis is stabilized at the anterior superior iliac spine of the contralateral side. Instruct the patient to indicate whether symptoms are provoked by the assumed position. General mobility can be estimated by measuring the distance from the lateral knee of the test leg to the treatment surface. If tolerated, overpressure can be placed at the medial surface of the knee toward the treatment surface. This additional pressure may elicit symptoms when passive stabilizers of the joint are loaded in this end-range position.


Pain (groin, lateral hip region, buttock) that resembles the patient’s primary symptoms is considered a positive finding, although identification of a specific pain generator with this test is difficult. The location of symptoms produced during this test must be considered when attempting to differentiate between hip joint involvement (typically groin pain) and sacroiliac joint dysfunction (often buttock pain).65 Differences in general hip mobility between the involved and noninvolved extremity should also be noted.

The studies examining diagnostic accuracy of the FABER test are inconsistent in regard to condition specificity, study methods, and overall quality.20,85 The FABER test has a reported sensitivity range of 57% to 100% and a specificity range of 25% to 100% when used to identify intraarticular disorders.85,86 Martin and Sekiya87 reported a positive likelihood ratio of 0.73 (95% confidence interval [CI]: 0.41, 0.77) and a negative likelihood ration of 2.2 (95% CI: 0.8, 6).

Flexion Adduction Internal Rotation Test

The flexion adduction internal rotation (FADIR) test is intended to identify symptomatic anterior impingement occurring at the hip joint (Fig. 4-9). The patient is placed in a position associated with anterior hip joint impingement, and symptom reproduction is monitored. It is suggested that patients with acetabular labral tears secondary to FAI often report pain with this test.


Figure 4-9 The patient is placed in the flexion adduction internal rotation (FADIR) test position. Complaints of groin pain are associated with symptomatic femoral acetabular impingement.


The patient assumes the supine position. The symptomatic hip and knee are passively flexed to 90 degrees. The hip is then passively internally rotated and horizontally adducted to the end ROM. Instruct the patient to note provocation of symptoms during performance of the test.


Pain (typically in the groin region) that reproduces the patient’s primary symptoms is considered a positive finding. Clinicians should exert caution when interpreting pain that occurs in areas other than the groin region. Tension or pressure placed across soft tissues (muscle, tendons, bursae) may elicit pain in other areas around the hip region.

When attempting to identify acetabular labral tears or other symptomatic intraarticular disorders, the FADIR test has a reported sensitivity range of 75% to 100%, and specificity range of 10% to 100%.11,87,88 In a systematic review, Reiman and associates88 reported a negative likelihood ratio range from 0.04 to 2.2 and a positive likelihood ratio range from 0.86 to 2.4.

Internal Rotation Over Pressure Test

The internal rotation over pressure (IROP) test is intended to identify symptomatic hip joint disorders (Fig. 4-10). The patient is placed in a position associated with anterior hip joint impingement; anterior-to-posterior pressure is then applied through the femur, and symptom reproduction is monitored. It is suggested that patients with acetabular labral tears and other intraarticular disorders often report pain with this test.


Figure 4-10 Internal Rotation and Over Pressure (IROP) Test. The patient is placed in 90 degrees of flexion and end-range internal rotation. A posteriorly directed force is placed through the femur. Reproduction of pain (typically in the groin) indicates an intraarticular hip disorder.


The patient assumes the supine position. The test hip and knee are passively flexed to 90 degrees. The hip is then passively internally rotated to the end ROM. Posterior pressure is then applied through the axis of the femur. The patient is instructed to note provocation of symptoms during performance of the test.


Pain (typically in the groin region) that resembles the patient’s primary symptoms is considered a positive finding.86 Clinicians should exert caution when interpreting pain that occurs in areas other than the groin region. Tension or pressure placed across soft tissues (muscle, tendons, bursae) may elicit pain in other areas around the hip region.

A small body literature has examined the IROP test. Maslowski and colleagues86 found sensitivity and specificity to be 0.91 (95% CI: 0.68, 0.99) and 0.18 (95% CI: 0.05, 0.40), respectively. Additionally, these investigators calculated a negative predictive value of 0.17 (95% CI: 0.04, 0.40) and positive predictive value of 0.88 (95% CI: 0.67, 0.98).86

Log Roll Test

The log roll test is intended to identify anterior capsular-ligamentous hyperlaxity of the hip joint (Fig. 4-11).12 Additionally, this test has been described as a method of assessing symptoms of intraarticular disorders.65


Figure 4-11 Positive Log Roll Test Result. After the hips are passively moved through internal and external rotation, the left foot is rotated further outward. This may indicate anterior laxity of the left hip joint.


The patient assumes the supine position. The examiner grasps the patient’s thighs, and the hips are moved through passive internal and external rotation. After the maneuver is performed several times, the hips are allowed to rest. The resting positions of the involved and noninvolved extremities are compared.


A notable increase of external rotation ROM in the involved hip is considered positive for hyperlaxity of the anterior capsular-ligamentous joint structures. Additionally, motion-induced pain in the groin or anterior lateral region of the thigh may indicate an associated intraarticular disorder of the hip joint. No diagnostic validity has been reported for the log roll test.89

Resisted Straight Leg Raise Test

The resisted straight leg raise test is intended to identify potential irritability of the anterior joint capsule or acetabular labrum (Fig. 4-12).20 Isometric contraction of the iliopsoas muscle is thought to place tension through the tendon across these structures.


Figure 4-12 Resisted Straight Leg Raise Test. The patient is asked to perform a straight leg raise maneuver against resistance. Reproduction of groin pain may indicate irritability of the anterior hip capsule, acetabular labrum, or iliopsoas complex.


The patient assumes the supine position. The test hip is actively flexed (knee remains extended) to approximately 30 degrees. The patient is instructed to maintain this movement as the examiner applies force into extension. The patient is instructed to note if groin pain is provoked by the test procedure.


The reproduction of groin pain when an extension force is applied to the patient’s hip may indicate irritability of the anterior hip capsule, acetabular labrum, or iliopsoas complex.86 Maslowski and associates86 found a sensitivity of 0.59 (95% CI: 0.34, 0.82) and specificity of 0.32 (95% CI: 0.14, 0.55). They calculated a negative likelihood ratio of 1.28 and a positive likelihood ratio of 0.87.

Posterior Rim Impingement Test

The posterior rim impingement test is used to assess the congruence of the posterolateral aspect of the femoral neck and the posterior acetabular rim clinically (Fig. 4-13).75


Figure 4-13 Posterior Rim Impingement Test. The patient is supine with the legs hanging freely. Both knees are drawn toward the chest, and the leg not being tested is stabilized by the patient. The clinician lowers the test hip into extension. Then the hip is passively abducted and externally rotated. Reproduction of posterior symptoms may indicate posterior hip impingement.


This test is performed by positioning the patient supine at the foot of the examination table and allowing the legs to hang freely at the hip. Instruct the patient to draw both knees up toward chest. While the patient holds the lower extremity not being examined in this flexed position, the clinician lowers the patient’s opposite leg off of the table into a position of extension. From this position, the hip is abducted and externally rotated in an attempt to reproduce the patient’s symptoms.75


Reproduction of the patient’s posterior hip pain when the leg is taken through this arc of motion may indicate posterior impingement between the posterior acetabular rim and the posterior aspect of the femoral head and neck. It has also been reported that if anterior pain is recreated in the position, it may indicate the presence of hip instability.1,75 Data to evaluate the clinometric properties of this test are scant.

Clustering of Clinical Tests

A limited but growing body of research has examined the use of clinical tests in patients with nonarthritic hip pain. More recent studies have often focused on the use of clinical tests and the population of patients with FAI. Martin and Sekiya87 conducted a study that examined the interrater reliability of the FABER test, FADIR test, log roll test, and greater trochanter palpation in patients with a mean age of 42 years (range, 18 to 76 years; SD, 15.4). These investigators found moderate to substantial agreement for all four tests. Acceptable reliability (moderate or greater as defined by a kappa coefficient >0.40) was found for the FABER test, log roll test, and tenderness with greater trochanter palpation. Kappa coefficients with 95% CIs were 0.63 (95% CI: 0.43 to 0.83) for the FABER test, 0.58 (95% CI: 0.29 to 0.87) for the FADIR test; 0.61 (95% CI: 0.41 to 0.81) for the log roll test, and 0.66 (95% CI: 0.48 to 0.84) for tenderness to palpation at the greater trochanter. All four tests demonstrated low bias index values (0.06 to 0.08). Higher bias index values can inflate the kappa coefficient. However, because of a high prevalence index (0.76) for FAI, the FADIR test was not considered reliable. A high prevalence index is correlated with an increased likelihood that the test result is positive by chance agreement.

Maslowski and colleagues86 examined pain provocation maneuvers before and after diagnostic intraarticular injection to determine the validity of the tests in the diagnosis of intraarticular hip disorders. If pain decreased greater than or equal to 80% after the injection, the symptom was considered to originate from within the hip joint. They found the most sensitive tests to be the FABER test, with a sensitivity of 0.82 (95% CI: 0.57 to 0.96), and the IROP test, with a sensitivity of 0.91 (95% CI: 0.68 to 0.99). The IROP test is performed similarly to the FADIR test, with added posterior overpressure. None of the tests showed high specificity (e.g., most had many false-positive results), with the resisted straight leg raise showing the highest value of 0.32 (95% CI: 0.14 to 0.55). The tests with the highest positive predictive value were the IROP and FABER tests, with respective values of 0.47 (95% CI: 0.29 to 0.64) and 0.46 (95% CI: 0.28 to 0.65). The IROP demonstrated the highest negative predictive value of 0.71 (95% CI: 0.25 to 0.98). These tests seem to have the ability to identify pathologic processes when present; however, they also tend to be associated with a high false-positive rate. Thus, a complete examination offers the best clinical utility, with special tests reserved as a means of confirmation. The results of this study justify the use of these tests for purposes of screening, as opposed to confirming specific disorders.

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Apr 27, 2020 | Posted by in ORTHOPEDIC | Comments Off on Femoral Acetabular Impingement and Labral Tears
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