Clinical Presentation

A careful history and physical examination should be performed to appropriately elucidate the cause of the patient’s symptoms. The location of the pain is important because intra-articular hip pain most commonly presents in the groin but may also present on the side of the hip, in the buttock, and may refer to the anteromedial knee via the obturator nerve. Patients with FAI or other intra-articular pathologic condition may make a c-sign when describing their pain, grasping the hip in the c-shape. Buttock pain and pain radiating down the posterior leg should alert the practitioner to the possibility of pathologic state of the lumbar spine. Pain in the lateral aspect of the hip may indicate trochanteric bursitis or iliotibial band friction syndrome. Pain that is strictly medial may indicate adductor muscle disease or hernias. Pain that presents superior to the inguinal ligament and radiates to the groin can be a presentation of a sports hernia or intra-abdominal, urologic, or gynecologic disease. The description of the pain can point the practitioner in a particular direction. Dull ache with intermittent sharp symptoms can represent any number of pathologic states. However, shooting or electric pain with numbness or tingling is often neurologic in origin.

The onset and provocation of the pain can often lead the practitioner to an appropriate diagnosis. Traumatic events should be carefully investigated in terms of the position of the leg at the time of the event and force directed against it because this will give clues to the structures and muscles involved. Frank dislocation of the native hip can also result in the late sequelae of avascular necrosis. Pain with deep flexion is characteristic of labral tears or chondrolabral junction injuries. These can also present with external rotation and extension. Participation in certain sports activities has been associated with particular injuries. Labral tears are more common in patients who participate in hockey, football, gymnastics, soccer, ballet, running, yoga, and surfing. Runners are at high risk for iliotibial band friction syndrome and iliopsoas tendinitis. Mechanical symptoms indicate labral tears and chondral lesions. Painful clicking or snapping with flexion and extension is the presenting complaint of internal and external snapping hip (coxa saltans).

Medical History

Past medical history can give particular clues that should not be ignored, even in the young patient. A birth history indicating possible developmental dysplasia of the hip (DDH) should be elicited (even if the eventual diagnosis is made radiographically). First-borns, females, breech births, and oligohydramnios are the classic risk factors for DDH. It is important to know if patients had prior interventions for congenital hip dysplasia. A history of Legg-Calvé-Perthes or slipped capital femoral epiphysis may influence the choice of treatment and need for surgical intervention. A history of childhood obesity and endocrine disorders may raise suspicion for undiagnosed or subtle slipped capital femoral epiphysis. Any history with risk factors for avascular necrosis should be carefully teased out (eg, steroid use, alcohol, diving, human immunodeficiency virus infection [HIV], AIDS, antiretroviral therapy).

Physical Examination

The physical examination is a crucial portion of the diagnosis. The patient should first be observed ambulating. This exercise is most commonly done by watching the patient walk to the examination room before their knowledge of observation. Antalgic gait patterns should be observed carefully to help differentiate hip and knee disease. Knee or hip flexion contractures may also masquerade as antalgic gait. The practitioner should pay attention to foot progression angle as a clue for determining abnormal acetabular version. A Trendelenburg gait should be confirmed with the Trendelenburg sign and strength testing of the abductor muscles. Subtle abductor weakness can be present in patients with DDH. Abductor muscle weakness also increases the joint reactive force and may exacerbate problems that might not otherwise cause patient discomfort. The subtleties of abnormal gait may help in specific diagnoses but may also identify deficiencies and targets for specified therapy. Studies have shown that patients with symptomatic FAI have lower voluntary motor contraction in all hip muscle groups (adduction, abduction, flexion, internal and external rotation) as well as lower electromyography (EMG) activity in certain muscles such as the tensor fasciae latae. This can lead to specific kinematic and kinetic differences during gait. A study by Hunt and colleagues compared 30 subjects with symptomatic FAI scheduled for surgery with 30 control subjects without FAI. They found that the subjects with FAI had a slower walking speed with slower cadence. Kinematically, the FAI group exhibited significantly less peak hip extension, adduction, and internal rotation during stance. Physical therapy targeting specific deficits may have a role in the treatment of patients with FAI, or comparative kinematic measurements may have a role in determining the success of the operative therapy. However, this has not been formally studied.

The patient should be examined standing as well as supine. Leg-length differences should be noted and compared with radiographs (full-length films should be obtained if there is any equivocation). Range of motion should be carefully tested and compared with the asymptomatic leg. During testing, attention must be paid during hip flexion and extension to detect flexion contractures. This can be done by having the patient flex both knees to the chest and then extend 1 knee at the time, thus removing lumbar compensation. The Stinchfield test (resisted hip flexion with the leg straight and 6 inches off the table) can help diagnose intra-articular problems because it indirectly loads the joint via muscle contraction. There are several tests for impingement, including flexion abduction external rotation (FABER) and flexion adduction internal rotation (FADIR). The extreme of flexion alone may cause impingement and symptoms may also be reproduced with hip external rotation and extension. The FABER test may also be positive with sacroiliitis. However, the location of this pain is usually over the sacroiliac joint and not in the groin, buttock, or lateral hip as with FAI. The Ober test helps determine iliotibial band tightness. Clear points of tenderness that lead to specific diagnoses include the bursa over the greater trochanter and over the iliotibial band insertion on Gerdy tubercle. Tenderness in the groin may represent iliopsoas disease, a hernia, or simply an inflamed hip capsule. A straight leg raise eliciting pain in the buttock (ipsilateral or contralateral) or reproducing radiating pain down the leg is highly suspicious for lumbar disease. Nerve tension signs, muscle strength, sensation, and reflexes should all be tested.

Differential Diagnosis

A logical and systematic approach is helpful in developing a differential diagnosis for hip pain. There are several schemas that may be useful. One is differential diagnosis by process as seen in Table 1 . Another is differential diagnosis by anatomic location, as seen in Table 2 .

Imaging

Imaging is of particular importance in reaching the correct diagnosis but certain pitfalls must be avoided. The correct interpretation of plain radiographs relies first and foremost on obtaining adequate films. Initial films include an anteroposterior (AP) pelvis with neutral rotation. When performed and interpreted adequately, this single view contains a wealth of information. The film should include the lower lumbar vertebrae as well as the proximal femora below the lesser trochanters. The practitioner should ensure that the film is neither an inlet nor an outlet view with the tip of the coccyx 3 to 4 cm from the pubic symphysis. On this view, the standard pelvic lines may be traced. A center-edge angle (CEA) and Tönnis angle can be calculated and crossover, posterior wall, and ischial spine signs observed for relative retroversion. The CEA of Wiberg ( Fig. 1 ) is the angle formed between the 2 lines passing through the center of the femoral head, 1 of which extends to the lateral edge of sourcil and a line perpendicular to a horizontal line joining the centers of the 2 femoral heads (of the 2 hips). The normal Wiberg angle in an adult is greater than 25°. The CEA greater than 40° is usually considered abnormal and may indicate pincer impingement. A CEA less than 25° indicates DDH. The Tönnis angle ( Fig. 2 ) is formed by the intersection of a horizontal line connecting the femoral head centers and the line that passes through medial edge of the sourcil to its lateral edge. An angle of less than 0° may indicate impingement and an angle of greater than 10° may indicate dysplasia or instability. The crossover sign indicates acetabular retroversion and is determined when the shadow of the anterior wall crosses the shadow of the posterior wall. A hip with a normal pelvic inclination should have the anterior and posterior rims join at the edge of the acetabulum. A positive crossover sign is often accompanied by an ischial spine sign in which the ischial spine protrudes beyond the ilioischial line into the pelvis and is prominent. The posterior wall sign is positive when the posterior wall is medial to the center of the femoral head and also indicates retroversion. Superior migration and extrusion of the femoral head are also notable signs of dysplasia and subtle changes can be detected by a break in Shenton line. The practitioner should look for signs of coxa profunda (fossa acetabuli touches or is medial to the ilioischial line) and protrusion acetabula (medial aspect of femoral head is medial to ilioischial line). A cross-table lateral is unreliable in determining acetabular version and the reader may also miss head-neck offset abnormalities. A frog-leg lateral may be useful in elucidating proximal femoral disease. A Dunn lateral view (flexion-abduction) is often used to better appreciate a cam lesion. The faux profile view can aid in evaluation of anterior coverage of the femoral head. On this view one can measure the anterior CEA in a similar fashion to measuring the lateral CEA on the AP radiograph. An anterior CEA less than 20° indicates a deficient anterior wall.

CEA.

Tönnis angle.

Advanced imaging is commonly performed in young patients with hip pain. Ultrasound can play a role in the diagnosis and management of certain tendinopathies, including tendinitis and tears of the abductors and iliopsoas, as well as trochanteric bursitis. Advanced cross-sectional imaging includes computed tomography (CT) and MRI, with or without intra-articular contrast. Further advanced imaging includes specialty MRI scans that examine the status of the articular cartilage, including T1-rho and delayed gadolinium-enhanced MRI of cartilage (dGEMRIC). MR arthrograms are valuable tools for evaluating labral tears and chondral lesions with relatively high sensitivity and specificity but are limited by only fair interobserver reliability as well as a lower reliability for detecting delaminated but not detached chondral lesions. A study by Keeney and colleagues examined 102 hips comparing MR arthrography with arthroscopic findings. In that study, magnetic resonance arthrography showed a sensitivity of 71%, specificity of 44%, positive predictive value of 93%, negative predictive value of 13%, and accuracy of 69% when evaluating labral disease. With respect to articular cartilage disease, MR arthrography had a sensitivity of 47%, specificity of 89%, positive predictive value of 84%, negative predictive value of 59%, and accuracy of 67%. A significant concern with MR arthrography, beyond the modest diagnostic accuracy, is the interpretation. Reurink and colleagues compared 2 radiologists examining MR arthrograms of 95 hips scheduled for arthroscopy. They found a kappa of 0.268, indicating fair reliability at best. CT arthrography can also be used for assessment of the labrum and cartilage with high sensitivity and specificity but is less commonly used because it delivers a relatively high radiation dose. Nishii and colleagues reported on the use of isotropic high resolution CT arthrography in 20 hips compared with arthroscopic findings. With respect to labral tears, a sensitivity of 97%, specificity of 87%, and accuracy of 92% was found. For diagnosis of cartilage lesions, 88% sensitivity, 82% specificity, and 85% accuracy was reported.

With the aid of 3-T magnets, several MRI techniques have been developed that demonstrate the ability to examine cartilage quality. As the availability of 3-T MRI becomes more widespread, these techniques will likely become more commonly used in clinical practice. T2-MR mapping is able to distinguish between superficial and deep cartilage layers based on distribution of water relaxation times. Patients with hip dysplasia and normal radiographs have demonstrated high signal in the superficial layer using T2-mapping compared with healthy controls. T1-rho MRI is a technique that is sensitive to low frequency chemical exchange between water molecules and the extracellular matrix of hyaline cartilage, revealing an inverse correlation between proteoglycan content and relaxation times. Rakhra and colleagues compared 10 hips in symptomatic subjects with cam-type FAI to 10 controls. The control group demonstrated a T1-rho value trend, increasing from deep to superficial cartilage layers ( P = .008). The FAI group demonstrated loss of this trend. The deepest third in the FAI group demonstrated greater T1-rho relaxation values than controls ( P = .028). This suggests that the early cartilage changes in the FAI group not appreciated on normal MRI or plain radiographs can be teased out. Aside from clear applicability, the current downsides to T1-rho imaging include the specialized technology needed as well as the labor-intensive cartilage mapping required. Another recent, and more heavily studied, MRI development is dGEMRIC. The technique involves intravenous administration of gadolinium followed by a period of activity and subsequent MRI. The technique is sensitive to the charge density of glycosaminoglycans and has become a validated modality for detecting arthritis. This imaging modality has established clinical utility. Studies have shown that the failure of pelvic osteotomies rises steeply in patients with a dGEMRIC index of less than 390 msec. This further supports the evidence that articular damage is poorly predictive of outcomes and this technology could become useful to develop more sensitive and specific cutoff values for hip preservation procedures than the current Tönnis grading system. The main downside to dGEMRIC is the intravenous administration of gadolinium and its inherent risk of nephrogenic systemic fibrosis or nephrogenic fibrosing dermopathy. Although many of the new imaging techniques are in their relative infancy regarding clinical utility, they hold promise for better patient selection and outcome measurement.

Aspiration or Injection

An intra-articular injection of a local anesthetic agent can provide both temporary pain relief and be a valuable diagnostic tool for differentiating from extra-articular causes of pain. Studies have shown injections to be safe and effective at reducing pain for up to 3 months in hip osteoarthritis, and the degree of relief has been correlated with the radiographic severity of arthritis. The efficacy of this intervention has not been fully studied in other diagnoses. It is advisable for patients to keep a journal for the period surrounding the injection because the effectiveness of the injection has often decreased by the next clinic visit. Counseling younger patients without radiographic osteoarthritis of the purpose of this diagnostic tool can help avoid patient frustration with the outcome. Injections can also be directed into the iliopsoas tendon sheath or trochanteric bursa and can provide significant pain relief. If infection is suspected, aspiration is a crucial part of diagnosis but should not delay treatment in the native hip. Both aspiration and injection should be performed by a qualified practitioner under radiographic or ultrasound guidance.

Extra Tests

EMG and nerve conduction studies can be helpful in differentiating nerve compression syndromes and radiculopathy. Unfortunately, certain muscles groups around the hip are difficult to test due to their depth in the soft tissue.

Treatment Options

The treatment options for all possible conditions affecting the hip is beyond the scope of this article. Instead, the focus is on anatomic disease with possible surgical interventions. Labral tears, FAI, and dysplasia often lie on a spectrum of severity, and associated pathologic states should be carefully weighed before treatment ensues.

Nonoperative Management

The treatment of many conditions affecting the hip of a young patient should begin with nonoperative management. The initial nonoperative measures include activity modification, administration of nonopioid analgesics and topical anesthetics, anti-inflammatories, physical therapy, chiropractic or osteopathic therapy, weight loss, and injections. Overall, the quality of evidence for nonoperative management is low. A meta-analysis of 53 papers examining nonoperative treatment of FAI found only 5 papers with any experimental analysis. All of these were small case series or descriptive epidemiologic studies of low or very low quality. Several similarities were found in the studies that may aid in advising patients. First, nonoperative management may improve symptoms in certain patients. Second, attempts to improve passive or active range of motion may be counterproductive given the mechanical nature of the deformity. Overall, there is little harm in attempting a course of nonoperative management with therapy and counseling regarding activity modification. Short-term use of anti-inflammatories may be helpful to progress the patient through a difficult period of symptoms. Long-term use of anti-inflammatories includes significant risks such as gastrointestinal distress, bleeding, myocardial infarction, and stroke, and should be pursued with caution.

Labral Tears

Which labral tears are most amenable to repair remains a matter of controversy. Careful diagnostic evaluation includes appropriate imaging, and intra-articular injection should be strongly considered before treatment. A long trial of nonoperative management should be the norm before any surgical intervention. If surgical intervention is deemed necessary, the surgeon should carefully address the labral tear and any underlying anatomic abnormality that could lead to recurrence. There is no consensus regarding arthroscopic versus open repairs. Proponents of the arthroscopic approach note the ability to visualize the central compartment and small, minimally invasive incisions. There is no literature comparing outcomes between arthroscopic in the supine or lateral decubitus positions. Despite being minimally invasive, there are significant risks, including neurovascular injury either from the instruments or traction. Ankle fractures from the positioning boot are another known risk. Arthroscopically assisted, mini-open procedures have been described without the use of a traction table. Advantages to the open approach include a relatively small incision that can be extended for hip arthroplasty or periacetabular osteotomy (PAO), a relatively short procedure time, lack of need for a specialized table, and avoidance of traction. Both arthroscopic and mini-open procedures allow for visualization and repair of the labrum, as well as the ability to address osseous lesions involved in FAI. However, both procedures are limited in their ability to address posterior lesions.

Over the last decade, there has been an increasingly large body of literature regarding the treatment of labral tears. Almost all studies are low-grade evidence in case series, prospective cohorts, and small randomized controlled trials. However, outcomes have been good in carefully selected subjects. A review of literature by Robertson and colleagues found a patient satisfaction rate of 67% at 3.5 years with 50% relief of mechanical symptoms. There is some evidence that repair of the labrum is a better option than debridement. A systematic review of the treatment of labral tears during surgery for FAI looked specifically at debridement versus repair. The investigators found a significant improvement in patient outcomes in the modified Harris hip score of 7.4 points favoring repair. It is also critical to recognize that up to 90% of patients with labral tears have an underlying structural abnormality.

Femoroacetabular Impingement

FAI is defined as abnormal femoral and/or acetabular morphology resulting in adherent contact between the 2 surfaces. As a result, there is supraphysiologic motion and repetitive loading that leads to soft tissue damage. The entity is typically grouped into cam, pincer, or combined cam-type and pincer-type. Usually pain presents in the groin, radiating laterally toward the greater trochanter and medially toward the adductors. Symptoms may rarely radiate to the buttock and down to the medial knee. Pain is often positional and exacerbated by flexion or prolonged sitting. There is a distinct loss of motion of the hip, particularly in flexion, abduction, and internal rotation. Imaging signs consistent with FAI include a crossover sign, ischial spine sign, increased CEA, increased alpha-angle on CT or Dunn radiograph, and small cysts at the femoral head neck junction (ie, herniation pits). Labral tears and cartilage delamination can occur as a result of FAI. Another distinct, although rare, impingement entity is femoral-ischial impingement and the practitioner should be aware of patients with extremely low offset.

Whether or not FAI is a prearthritic condition or a reaction to an arthritic process remains a debate. Ganz and colleagues have championed that greater than 90% of hip osteoarthritis may be attributable to pre-existing deformity. However, cross-sectional and epidemiologic studies create some doubt in this claim by revealing morphologic abnormalities in a large, asymptomatic portion of the population.

Treatment of FAI has shown relatively good results in a carefully selected population who have Tönnis grade 0 or 1 osteoarthrosis. Arthroscopy allows access for treatment of anterior cam lesions and labral repairs. There is increased difficulty in addressing acetabular lesions, cartilage damage, or impingement in the inferior and posterior aspects of the hip. Additionally, neurovascular risks from instruments and prolonged traction are disadvantages of this intervention. The mini-open option via 4 cm modified Smith-Peterson approach can address both femoral and acetabular lesions without difficulty, does not require a special table or traction, and has a relatively quick recovery. However, there is a limitation in the access to posterior lesions as well as the central compartment. Surgical hip dislocation with a trochanteric osteotomy can address the full spectrum of femoral and acetabular pathologic conditions with good results but is associated with significant surgical morbidity. If the patient has acetabular retroversion and concomitant cam-type FAI, then a PAO should be considered. For the patient with posterior impingement and excessive posterior wall coverage, a reverse PAO is an option but outcomes have been variable.

Overall outcomes from treatment of FAI are generally good with arthroscopic, mini-open procedures, or surgical hip dislocations. Literature reviews show that, overall, 75% to 90% of athletes return to sport at their preinjury level. Reduced pain and improvement of function are reported in 68% to 96% of patients with an improvement range of 2.4 to 5 points on the Merle d’Aubigné and Postel score. The heterogeneity of outcomes and lack of positive outcomes in some studies can be partially explained by the consistent findings that patients with pre-existing arthritis, advanced chondral degeneration, and older age had worse outcomes with faster progression to total hip replacement. This finding confirms that conservative patient selection is critical for success when considering hip preservation.

Cartilage Lesions

Most cartilage lesions are associated with labral tears and often with FAI or dysplasia. Major cartilage lesions are usually best treated with arthroplasty. However, other options exist, including chondroplasty, microfracture, articular cartilage repair or reattachment, autologous chondrocyte implantation (ACI), mosaicplasty, and osteochondral allograft transplantation (OAT). Most of these techniques are well described in the knee but outcomes in the hip are less reported. Microfracture is described for contained lesions less than 4 cm ² , and several case series have been published with generally favorable results. Byrd and Jones reported on microfracture during management of FAI in 58 hips with a grade 4 chondral defect, an intact subchondral plate, and healthy surrounding cartilage. The modified Harris hip score improved from 65 preoperatively to 85 at 2-year follow-up. The relative advantages of microfracture over other cartilage procedures are low expense and ease of performing. The durability of the subsequent fibrocartilage repair is unknown. ACI is performed in a staged manner in which chondrocytes are harvested from 1 joint, grown in a laboratory, and then reimplanted using a patch or with matrix-assisted ACI (MACI). Fontana and colleagues compared the outcomes of simple debridement versus MACI for management of hip chondral defects in 30 subjects with Outerbridge grade 3 or 4 lesions. The area of the defect was equal in both groups, as was the preoperative Harris hip score, with 48.3 in the MACI group and 46 in the debridement group. The investigators reported better clinical outcomes with MACI than with simple chondroplasty, with an average Harris hip score of 87.4 in the MACI group and an average score of 56.3 in the debridement group ( P <.05) at final follow-up. Mosaicplasty is the use of cylindrical cartilage plugs with subchondral bone attached to fill defects of large size. The technique has been well described in the knee but only small case series have been reported in the hip with good results. Girard and colleagues reported 10 subjects with femora head defects and an average age of 18 years with a variety of congenital hip diseases. Average lesion size was 4.8 cm ² and the average follow-up was 29.2 months. The Merle d’Aubigné and Postel score improved from an average of 10.5 preoperatively to an average of 15.5 postoperatively. The Harris hip score also improved from 52.8 preoperatively to 79.5 postoperatively. At 6 months postoperatively, CT arthrograms showed excellent graft incorporation with intact cartilage in all subjects. At final follow-up, none of the subjects required total hip arthroplasty (THA). The downsides to the procedure include donor site morbidity and the necessity for surgical hip dislocation. An OAT procedure may be appropriate for larger defects with subchondral bone loss. An early study by Meyers and colleagues had a 32% failure rate (8 out of 25 hips). More recently, Khanna and colleagues reported good outcomes in 76% of subjects (13 out of 17 hips). Failures, durability, and risk of disease transmission are the major concerns regarding OAT procedures. Overall, larger, high quality studies are needed to delineate the appropriate patients and lesions for cartilage restoration.

Dysplasia

There is a spectrum of abnormal hip morphology under the umbrella term of congenital hip dysplasia. This includes acetabular version, depth and coverage, proximal femoral deformities, and their combined resultant altered biomechanics and pathologic states. The spectrum can cause pain and labral disease either through too little bone, as seen in the undercoverage and anteversion of classic dysplasia, or too much bone, as seen in coxa profunda, the cam, and pincer FAI. Treatment of these morphologies in the prearthritic hip of the younger patient includes a variety of acetabular and proximal femoral osteotomies, combined with treatment of any underlying labral disease, and FAI. When indicated, a Bernese PAO can be combined with a femoral osteoplasty and labral repair through a single direct anterior incision ( Figs. 3–5 ). Certain femoral deformities may require a proximal femoral osteotomy. In general, these are complex procedures that require specialized training and have relatively high complication rates. A systematic review revealed a major complication rate of 6% to 37%, including symptomatic heterotopic ossification, major nerve injuries, intra-articular osteotomies, loss of fixation, and malreduction.

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