Athlete with Hip Pain

Agam Shah

Jonathan Fallon

INTRODUCTION

Athletic hip pain is a common complaint among athletes that historically has been hard to diagnose and treat. The vague nature of hip pain along with the complex anatomy has made it a diagnostic and therapeutic challenge. The advent of magnetic resonance imaging (MRI), improved exam techniques, and better understanding of the pathology surrounding the hip, including the bony, ligamentous, neurovascular, muscular, and intra-articular diseases, have allowed for the diagnosis and treatment of athletic hip pain to become more manageable and an area of active research. This chapter will focus on the overall approach to hip pain in the athlete based on a sound understanding of anatomy and the physical exam. The second half of the chapter will focus on the diagnosis and treatment of common conditions found in athletes that can cause hip pain.

FUNCTIONAL ANATOMY

The hip joint consists of the articulation of the acetabulum with the proximal femur, including the overlying musculature, ligamentous and other soft-tissue structures, and associated neurovascular structures.

The acetabulum serves as the fusion point of the three parts of the innominate bone: the ilium, the ischium, and the pubis. The ilium is located posterior-laterally and articulates with the sacrum at the sacroiliac joint and gives rise to a broad expansion termed “the iliac crest.” The ischium is located posterior-inferiorly and is bordered by the ilium superiorly and pubis anteriorly. The pubis forms the third part of the innominate bone and is found in the anterior aspect of the pelvis. All three bones meet at the center of the acetabulum. The acetabulum is a dome-shaped structure that approximates a hemisphere, with the concave portion covered by articular cartilage.

The proximal femur comprises the bony elements of the thigh and articulates with the pelvis at the hip joint. The femur is a diaphyseal structure that broadens proximally to form the trochanteric ridge, greater trochanter, lesser trochanter, and femoral neck. The neck forms an average angle with the shaft of approximately 130 degrees (neck shaft angle) and is found to have an average anteversion angle of 15 degrees. Deviations from normal anatomic geometry can lead to improper mechanics and injury, that is, femoroacetabular impingement (FAI) or stress fracture.¹

The femoral head forms two thirds of a sphere and is covered with articular cartilage. The ligamentum teres arises from the fovea of the femoral head and attaches to the center of the acetabulum in the pulvinar fossa.

Unlike the shoulder joint, the hip joint is a highly constrained ball-and-socket joint, with motion limited predominantly by its bony configuration. Additionally, the joint is surrounded by three strong ligaments: the pubofemoral ligament inferiorly, the ischiofemoral ligament posteriorly, and the iliofemoral ligament anteriorly (also known as the ligament of Bigalow). These three ligaments integrate to form the hip joint capsule. The capsular attachments are from the intertrochanteric line on the femur to a few millimeters superior to the acetabular rim.

The labrum is a fibrocartilagenous structure that is attached to the acetabular margin. The labrum serves to deepen the hip socket and contributes to the normalization of joint reactive forces across the hip joint. Although the labrum’s function remains controversial, studies show that the labrum does not participate in direct load transmission.²

The muscles around the hip can be divided into two layers, superficial (Table 17.1) and deep (Table 17.2). Although injury can occur to any of these muscles, there is a general agreement that muscles that cross two joints are more likely to sustain a strain injury than muscles that cross a single joint for two reasons. First, muscles that cross two joints have been found to be less flexible and experience a greater strain per applied force when compared to single-joint muscles.

Second, muscles that cross two joints have a higher ratio of type II fast-twitch fibers, leading to more violent contractions.³ Special attention should be given to four muscles that are more commonly injured. The gluteus maximus and the tensor fascia lata are superficial posterior lateral structures that combine to form the iliotibial band (ITB), which has been implicated in the etiology of trochanteric bursitis and external snapping hip syndrome. The iliopsoas muscle can be associated with internal snapping hip syndrome and is the most common muscle involved with hip flexor strain. Lastly, the adductor longus muscle is the most commonly involved muscle in adductor strains. Free body analysis demonstrates that the adductor longus has the least mechanical advantage on adduction of the hip, making it susceptible to the most strain.

TABLE 17.1 Superficial Muscles Surrounding the Hip Joint

Name of Muscle	Origin	Insertion	Nerve Supply	Action	Distinguishing Characteristics
*Anterior Group*
Sartorius	Anterior-superior iliac spine	Anteromedial surface of proximal tibia	Femoral nerve	Flexes, abducts, laterally rotates thigh at hip joint	Longest muscle in the body One third of pes anserine
*Lateral Group*
Tensor fascia lata	Iliac crest	Iliotibial band and then Gerdy tubercle	Superior gluteal nerve	Assists in extending the knee joint and abducting the hip	Can be responsible for external snapping hip
Gluteus medius	Outer surface of ilium	Greater trochanter	Superior gluteal nerve	Abducts hip joint	Injury to this muscle leads to trendelenburg gait
*Posterior Group*
Gluteus maximus	Surface of ilium, sacrum, and coccyx	Gluteal tuberosity of femur and iliotibial band	Inferior gluteal nerve	Extends and externally rotates the hip and extends the knee	Termed the “pelvic deltoid” by Henry Largest muscle in the body
*Medial Group*
Gracilus	Inferior ramus	Anteromedial surface of proximal tibia	Obturator nerve	Abducts hip and flexes knee	One third of pes anserinus
Adductor longus	Body of pubis	Linea aspera of femur	Obturator nerve	Adduct hip	–

TABLE 17.2 Deep Muscles Surrounding the Hip Joint

Name of Muscle	Origin	Insertion	Nerve Supply	Action	Distinguishing Characteristics
*Anterior Group*
Rectus femoris	Anterior inferior iliac spine and ilium	Quadriceps tendon into patella	Femoral nerve	Flexes hip and extends knee	Only quadriceps muscle that crosses the hip joint
Iliopsoas	Iliac fossa and T12-L5 vertebral bodies	Lesser trochanter	Lumbar plexus	Flexion, adduction, and external rotation of hip joint	Associated with internal “snapping hip syndrome”
*Lateral Group*
Gluteus minimus	Surface of ilium	Greater trochanter	Superior gluteal nerve	Abduction of hip joint	–
*Posterior Group*
Piriformis	Anterior sacrum	Greater trochanter	First and second sacral nerves	Externally rotate the hip joint	Most proximal of the short external rotators
Obturator internus	Obturator membrane and spine of ischium	Greater trochanter	Sacral plexus	Externally rotate the hip joint	–
Quadratus femoris	Ischial tuberosity	Quadrate tubercle of femur	Sacral plexus	Externally rotate the hip joint	Most distal of the short external rotators
Superior gemellus	Spine of ischium	Greater trochanter	Sacral plexus	Externally rotate the hip joint	–
Inferior Gemellus	Ischial tuberosity	Greater trochanter	Sacral plexus	Externally rotate the hip joint	–
*Medial Group*
Adductor brevis	Inferior ramus of pubis	Linea aspera of femur	Obturator nerve	Adduct the hip joint	–
Adductor magnus	Inferior ramus of pubis and ischial tuberosity	Posterior femur and adductor tubercle	Obturator and sciatic nerve	Adduct the hip joint	Muscle has dual innervation

EPIDEMIOLOGY

Muscle strain injuries are fairly common and occur as the result of forceful contraction of a stretched muscle. Eccentric contraction, or muscle contraction during elongation, is the most frequent type of contraction that causes this injury.⁴ A strain is the result of partial tearing of a muscle, generally at the myotendinous junction. Repetitive microtrauma can lead to chronic strains. Historically, soccer and hockey players are most prone to adductor strains. Poor adductor strength and conditioning has been found to be a risk factor for adductor strains.⁵ Some authors have concluded that decreased preinjury flexibility leads to muscle strain, but recent literature suggests that the two are unrelated.⁶ Strains to the iliopsoas muscle are an infrequent cause of hip pain. The mechanism of injury is usually a sudden resistance to hip flexion, that is, a collision while attempting to perform a kick. Patients with suspected strain will exhibit pain in the front of the proximal hip that radiates into the groin. Often, there will be a sharp pain in the groin, which increases with resisted hip flexion or passive external rotation. Patients with iliopsoas strains will not have pain or weakness with resisted knee extension, helping distinguish it from strains of the rectus femoris and gracilis muscles.

Apophyseal injuries and avulsion fractures typically occur in sprinters, jumpers, and soccer and football players. Once thought to be rare, these injuries are more common among the athletic population and comprised greater than 13% of pediatric pelvic fractures in one series.⁷ Typically, avulsion injuries are caused by a sudden eccentric contraction of a muscle; however, chronic overuse syndromes can present as apophysitis in the skeletally immature athlete (e.g., Sinding-Larsen dx and Osgood-Schlatter dx).³

Osteitis pubis is a painful inflammation of the pubic symphysis. This pathology occurs most commonly in the adolescent and early-adult athletic population. Causative mechanisms are not well understood, but investigators believe that the underlying feature involves overuse of the adductors and gracilis muscles.⁸ Alternative causes are hypothesized to include microstrains at the origins of these muscles, avascular necrosis (AVN) of the symphysis, osteochondritis desiccans at the symphysis, or fatigue fracture. Some believe that an imbalance between abdominal wall musculature and hip adductor strength can be a risk factor.⁸

Athletic pubalgia, also termed “Gilmore’s groin” or “sports hernia,” is a broad spectrum of injuries involving the inguinal ligament, conjoined tendon transversalis fascia, internal oblique muscle, external oblique muscle, and rectus abdominus insertion. There is thought to be an imbalance between the adductor muscle group of the thigh and the abdominal musculature, leading to a weakening and possible tearing of the structures of the pelvis floor. The pathology is noted to occur more frequently in males versus females.

Coxa sultans, more commonly known as “snapping hip,” is a term used to describe several different disease entities. Although these entities can occur in patients of any age, external and internal snapping hip tends to occur in patients in the late teens or early 20s.⁹ The common feature of all patients with snapping hip syndrome is that there is a reproducible audible or palpable “snap” with certain hip motion. There are three main categories of coxa sultans: external snapping hip syndrome, internal snapping hip syndrome, and intra-articular snapping hip syndrome. External snapping hip is the most common and is most often caused by thickening of the ITB or gluteus maximus snapping over greater trochanter.¹⁰ In contrast, internal snapping hip, often seen in ballet dancers,¹¹ is most often caused by the iliopsoas snapping over the iliopectineal eminence of the pelvis or over the femoral head.¹⁰ Intra-articular causes of snapping hip can be labral tears, loose bodies, or osteochondral injuries. Most patients with intra-articular causes have a history of trauma.

Acetabular labral tears have been reported as the most common form of intra-articular pathology in the hip. Increased shear forces in the hip joint have been suggested as a cause for labral tears. Five distinct pathologic entities have recently been linked to this condition: FAI, hip dysplasia, trauma, capsular laxity, and joint degeneration.¹²

FAI in the athletic population is thought to be caused by a combination of subtle morphologic variants in the acetabulum and/or proximal femur and use of the hip through an extreme range of motion.¹³ Posttraumatic deformities, deepened acetabulum (protrusion or coxa profunda), and acetabular retroversion are thought to be the most common anatomic variants that cause the femoral neck to repeatedly abut against the rim of the acetabulum. This pathologic impingement, either cam (femoral neck based) or pincer (acetabular based), causes chondral and labral damage that, if left untreated, can lead to early joint degeneration.¹⁴

AVN of the femoral head in the athletic population is an incompletely understood pathology that frequently affects patients in the third to fifth decade.¹⁵ Interrupted vascular supply secondary to lipid circulation and coagulation pathways are the most commonly cited mechanisms of subchondral bone death. Approximately 80% of cases have a predisposing risk factor, systemic steroid use, hypercoagulable states, and alcoholism, which is the most common. There have also been reports of AVN after traumatic subluxations of the hip in football players.¹⁶

Degenerative joint disease (DJD) can be the final common pathway of many disease processes that affect the hip, including osteoarthritis, traumatic arthritis, congenital hip dysplasia, systemic inflammatory diseases, and AVN (Table 17.3).
All of these entities result in the destruction of cartilage within the hip joint, increased friction with hip motion, and irritation of the surrounding synovium.

TABLE 17.3 Common Etiologies of Hip Arthritis

Osteoarthritis

Trauma

Rheumatoid arthritis

Infection

Reiter arthropathy

Psoriatic arthropathy

Avascular necrosis

Gout

Pseudogout

Ankylosing spondylitis

Hemophilia

Paget disease

Legg-Calvé-Perthes disease

Slipped capital femoral epiphysis

Developmental dysplasia of the hip

NARROWING THE DIFFERENTIAL DIAGNOSIS

Discerning the cause of hip pain in the athlete can be daunting due to the complex anatomy and large number of potential etiologies. The following is a list of common causes of hip pain in the athlete followed by appropriate history and physical exam findings that can help narrow the differential diagnosis:

Strain or avulsion injury
Osteitis pubis
Athletic pubalgia
Snapping hip syndrome (external and internal)
Labral tear
FAI
AVN
DJD
Stress fracture (femoral neck or pubic ramus – see Chapter 22, “Athlete with Stress Fracture”)
Referred pain from lumbosacral spine or gastrointestinal/gastrourinal process

History

As with any patient, significant diagnostic information can be gained from the injured athlete’s history. Physicians should discuss onset, duration, character, intensity, location, exacerbating factors, prior history, and quantification of the athlete’s pain. Use of a visual analog scale can provide consistent comparison throughout the treatment process. Information should also be gathered about the athlete’s training regimen, noting any recent changes in intensity, frequency, or equipment. Relevant medical and surgical history should also be gathered, including obstetric, gynecologic, and urologic. Any prior history of hip pain should be thoroughly explored, obtaining old records, films, or test when applicable and available. Finally, prior treatment modalities should be noted along with a measure of their success.

Location of hip pain will often be useful in arriving at an accurate diagnosis. Lateral hip pain associated with snapping or popping may suggest ITB friction syndrome, while painful snapping in the inguinal crease region may indicate iliopsoas tendonitis/bursitis or a labral tear. Diffuse deep groin pain that is gradual onset may suggest a femoral neck stress fracture in the appropriate setting. Diffuse hip pain in the older athlete that improves as the day progresses may indicate underlying hip osteoarthritis.

Pain that radiates past the knee or has any paresthesias or dysthesias may indicate referred pain from the lumbar spine.

Evidence-based Physical Exam

The physical exam of the hip and pelvis should begin with a general inspection of gait, posture, and pelvic and limb alignment. Normal and symmetric anatomic contours should exist when comparing the injured hip to the contralateral hip. In the setting of an acute injury, gross deformity, tenderness, inability to bear weight, ecchymosis, edema, or erythema may be present. Chronic or subacute injuries are more likely to be manifested in altered gait, limited range of motion, or persistent restrictive pain altering the athlete’s ability to participate in desired activities. Regions of tenderness, limited range of motion or strength, relevant neurologic findings, and muscle atrophy should all be documented on initial examination. Palpable landmarks that deserve attention include the greater trochanter, the superior and inferior iliac spines, and the femoral pulse.

When evaluating muscle strains and tears, regions of tenderness and rarely identification of palpable defects can isolate involved musculotendinous units. Active and passive range of motion should be tested in all planes. Strength and resistance testing should also be performed focusing on the specific action of the involved muscle. Although strains occur most commonly at the musculotendinous junction, points of origin and insertion should be palpated if an avulsion injury is suspected.⁴ Loss of strength in certain planes can be diagnostic in strain injuries, nerve damage, and avulsion injuries. Tenderness in the region of the superior pubic ramus and symphysis is suggestive of ramus stress fractures, osteitis pubis, or athletic pubalgia. Reproduction of this pain with passive abduction and resisted adduction is highly suggestive of osteitis pubis. Athletic pubalgia can have associated tenderness along the conjoined tendon, inguinal ring, or adductor origin. If a hernia is suspected, thorough examination of the abdominal wall, inguinal canal, scrotum, and testicles is indicated. Provocative testing for hernias include pain with resisted sit-ups and with resisted adduction with the hip externally rotated.¹⁷

The standing sign, the hop test, and the fulcrum test are well-described provocative maneuvers designed to reproduce the pain associated with stress fractures about the hip.¹⁸ A more thorough discussion is provided in the section of this text dedicated to stress fractures.

External and internal snapping hip syndrome can often be delineated by the position of the leg while reproducing the snapping sensation. With internal snapping hip, the symptoms can be reproduced by placing the patient supine, flexing and abducting the hip, followed by an extension and adduction maneuver. Pressure applied over the iliopsoas tendon at the level of the femoral head should block the snapping, thereby corroborating the diagnosis. The snapping sensation associated with external snapping hip can be reproduced by having a supine patient actively flex the affected hip with the examiner’s hand over the region of the greater trochanter. As with internal snapping hip, pressure at the point of snapping should block the event. Although there are no scientific data to delineate the specificity or sensitivity of these tests, they are generally considered the most effective test available. Ober’s test is helpful in confirming a diagnosis of external snapping hip. The test is performed with the patient in the lateral decubitus position with the affected hip up. With the knee flexed and the hip maximally extended, the hip is brought from a maximally abducted position to an adducted position. If the patient’s hip cannot be adducted beyond the midline, then the test is positive, indicating a tight ITB associated with external snapping hip.⁹

The “log roll” is thought to be the most specific indicator of intra-articular pathology. The passive rotation of the leg of a supine patient through maximal internal and external rotation allows for motion of the femoral head relative to the acetabulum and capsule without stressing the surrounding structures.²⁰

Physical exam tests suggestive of labral pathology include the flexion abduction external rotation test as well as the anterior-superior impingement test. The FABER test is performed with the patient supine; the involved hip is flexed, abducted, and externally rotated by the examiner while stabilizing the anterior superior iliac spine. The impingement test involves flexing, internally rotating, and adducting the hip of a supine patient. If the original pain is reproduced, these tests are considered positive. These tests are thought to be more sensitive for intra-articular pathology; however, recent studies have questioned their accuracy.²⁰, ²¹, ²² Both the FABER and impingement tests have demonstrated good interrater reliability and remain the best physical exam tests available to screen for labral pathology.

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