The acetabular labrum has been widely recognized as a source of hip pathology. The clinical manifestations of injury to this structure are being reported with increasing frequency. Injury to the labrum has been documented as a result of femoroacetabular impingement (FAI) or hip dysplasia, hip dislocation, athletic injuries, or it may have an idiopathic origin (1, 2, 3, 4). Labral tearing can result in hip pain and mechanical symptoms and has been implicated in the accelerated development of degenerative osteoarthritis (5). Surgical techniques to manage labral pathology have also developed rapidly. Initial techniques included surgical hip dislocation with labral débridement and management of associated pathology. Current arthroscopic techniques appear to lead to similar or improved initial outcomes, while allowing a shorter recovery period and more rapid return to activity (6).

The acetabular labrum itself is a complex structure consisting of a fibrocartilaginous rim composed of circumferential collagen fibers spanning the entirety of the acetabulum, becoming contiguous with the transverse acetabular ligament (TAL) and anchored through a well-defined 1 to 2 mm transitional zone of calcified cartilage at the acetabular rim. The labral surface immediately adjacent to the articular cartilage of the femoral head becomes continuous with the hyaline articular cartilage of the acetabular surface through a similar transitional zone (1). Histologically, the labrum is composed of dense connective tissue divided into bundles at the peripheral rim and transitions to fibrocartilage at the inner surface. The vascular supply is derived primarily from the joint capsule, originating from the medial and lateral circumflex, inferior and deep branch of the superior gluteal arteries (1,7,8). There is a relatively hypovascular zone within the internal substance of the labrum and extending to the distal margin that may predispose this area to injury from acute or repetitive trauma and lead to degenerative change. The peripheral attachment of the labrum near its bony attachment has been shown to have a robust vascular supply, and in conjunction with the highly vascularized synovium, there may exist the potential of labral neovascularization and healing in the setting of labral injury (1,7).

The complete physiological function of the labrum is not completely defined, but it appears to serve multiple purposes, including a limitation of extreme range of motion and deepening the acetabulum to enhance the stability of the hip joint. Studies have shown that the labrum contributes approximately 22% of the articulating surface of the hip and increases the volume of the acetabulum by 33% (1). This serves to dissipate the large forces across the hip with stride and athletic activities as these joint reactive forces can be as high as four times the body weight (9). The labrum also provides a sealing rim around the femoral-acetabular joint, enabling increased hydrostatic fluid pressure, which facilitates synovial lubrication and resistance to joint distraction (10).

The highly organized composition of the labral fibers provides exceptional radial tensile stiffness, while its low permeability assists in maintaining the articular fluid homeostasis. In conjunction with the TAL, it contains an inherent elasticity that allows excellent conformity with the articular surfaces during range of motion while providing for minor joint incongruities. This allows the labrum to function in its most important role of dissipating the high potential contact forces encountered by the hip joint during activity and weight bearing at any flexion angle.

Pathologic alterations of the acetabular labrum have classically been associated with developmental disorders of the hip including Legg-Calve-Perthes disease, developmental dislocation, and acetabular dysplasia. Injury to
the labrum from acute trauma, repetitive injury, and impingement syndromes have more recently been identified as a source of pain (2,3,11). Once injured or torn, the role of the labrum is compromised and can lead to further damage to surrounding structures in the hip, including the articular cartilage loading, delamination, and subchondral cyst formation. It has been shown that the loads across the femoral and acetabular articular cartilage in a labrum-deficient hip are up to 92% greater than those encountered with an intact labrum. Labral deficiency also imparts a decreased constraint of the femoral head, allowing the center of joint contact to displace laterally toward the acetabular rim, creating this focal area of increased articular forces. The mechanical stability of the hip may further be compromised due to the reduced resistance to hip distraction and disruption of the intraarticular hydrostatic environment. Such alterations in the kinematics of the native hip anatomy may contribute to the progression of hip osteoarthritis following labral injury (12, 13, 14, 15). This was initially evidenced by the increased incidence of osteoarthritis in patients with developmental dysplasia of the hip, chronic labral tears, and full-thickness chondral lesions (16). Attempting to improve the symptoms of hip pain while potentially reducing the progression of osteoarthritic degeneration of the femoro-acetabular joint have spurred significant interest in the operative management of labral tears and associated pathology.

The anatomic relationship of labral tears to underlying bony and musculotendinous hip pathology has been well defined in the literature. These include trauma, FAI, capsular laxity, and hip dysplasia. There is less evidence regarding the clinical usefulness of signs, symptoms, and examination in accurately detecting labral tears without further diagnostic testing. However, the most important initial step in the evaluation of hip pain is the history and clinical examination (17).

A labral tear can be the result of a traumatic event, usually involving an external rotation force with the hip in a hyperextended position (18). There may also be a chronic component without acute injury, with labral tearing occurring from microtrauma associated with repetitive activities during routine hip motion, such as with FAI. A careful history including any inciting trauma; onset, duration, and progression of symptoms; aggravating and mitigating factors; previous interventions; and activity-related consequences should routinely be obtained during the initial visit. It is frequently helpful to ask the patient to demonstrate the activities or extremity position that reproduces the symptoms, as this may assist in identifying the etiology of the complaint.

Reported symptoms of a labral tear may include pain, clicking, mechanical locking, instability, a feeling of giving way, or joint stiffness. Anterior groin pain is frequently associated with intra-articular complaints, and a high number of patients diagnosed with labral tears will report this findings. The pain associated with an intra-articular source may less commonly radiate to the posterior hip, buttock, greater trochanter, medial thigh, or knee. One must use caution as these symptoms are relatively nonspecific and do not confirm the diagnosis of a labral tear (19).

Other etiologies of the presenting symptoms must also be carefully considered to identify possible contributing sources. These include the urogenital system problems, sacroiliac (SI) joint pain, spinal pain, abdominal symptoms, soft tissue contusions, and abdominal wall pain. If there is a suspicion of an extra-articular component to the patient complaint, the history and physical examination must be adjusted appropriately (20).

The clinical evaluation of a patient with hip pain can be challenging and requires a systematic approach to the physical examination to aid the clinician in correctly identifying the source of the complaint. These symptoms may arise from both an intra-articular and an extra-articular source, and care must be taken to appropriately direct the diagnostic algorithm to successfully locate the source of the complaint and guide therapeutic interventions. After an appropriate history has been obtained, the physical examination can assist the physician in further narrowing the diagnosis (20).

A focused physical examination should include evaluation of the lumbar spine, SI joints, and the femoroacetabular joint. The examination of the hip can be complicated by the relatively common incidence of referred pain from genitourinary, visceral, and gynecologic etiologies to the area in question (21). These external sources of pain may masquerade as hip pathology and must be ruled out (4).

In patients with unilateral complaints, all objective examinations should be compared to the contralateral side. A gait examination, if able to be performed, is frequently the initial step in the evaluation. Particular attention should be placed on stride length, core balance, posture, and the duration of the stance phase of gait. One should also take care to notice evidence of scoliosis, limb-length discrepancy, muscular deficit, or joint contractures (22). The focused examination of the hip should include localizing areas of maximal pain or tenderness and any atrophic muscular changes identified with palpation. Intra-articular pathology will rarely be associated with external discomfort. Hip range of motion is assessed with comparison to the contralateral extremity in the supine position with all deficiencies documented. This should include measurement of flexion, extension, internal and external rotation, and any associated deficit or discomfort. Increased passive external rotation of the leg with the hip in neutral extension may indicate the presence of capsular laxity. Provocative testing is used to functionally
evaluate patient symptoms in various limb positions. Placing the hip into flexion/adduction/internal rotation places the anterolateral femoral head and neck into proximity with the anterior and lateral acetabular margin. This may cause compression of the labrum and associated pain in the presence of a labral tear. The FABER test consists of flexion/abduction/external rotation of the hip and places the iliopsoas tendon on stretch while stressing the SI joints. The Ober test assesses iliotibial (IT) band tightness with the patient in the lateral position with the symptomatic extremity in placed superiorly. A positive result is when the leg remains abducted while the hip and the knee are passively extended. A flexion contracture of the hip can be assessed with the Thomas test as it minimizes the ability to compensate for decreased hip extension with excessive lumbar lordosis. The contralateral hip is flexed, reducing lumbar lordosis and assessing full hip extension in the supine position. Assessment of a “snapping” sensation should also be performed as this may be due to the IT band gliding across the greater trochanter or the iliopsoas tendon riding over the anterior margin of the superior pubic ramus.

While the physical examination is a critical component to diagnosis, it should be noted that multiple studies have found that the diagnostic accuracy of clinical findings may be variable. One additional function of the examination is to guide the physician in ordering appropriate diagnostic tests to identify and confirm the source of symptoms (23,24). There is also a limited correlation between physical examination findings and those patients with true intra-articular hip pathology.

Imaging of the hip is a routine part of the diagnostic algorithm for management of intra-articular pathology and includes plain radiographs, computed tomography (CT), magnetic resonance imaging (MRI), and magnetic resonance arthrography (MRA). Plain radiographs of the pelvis are the mainstay in the initial evaluation of hip pathology and are excellent in the identification of fracture, dislocation, arthritic change, bony abnormalities including FAI and dysplasia, and identification of radio-opaque loose bodies. A standard radiographic series should include anteroposterior pelvis and lateral views (25). Certain radiographic findings may immediately lead the orthopaedic surgeon to suspect labral pathology, or identify another etiology responsible for the patient’s symptoms. These may include stress fractures, cam or pincer-type femoral acetabular impingement, excessive acetabular retroversion, joint space narrowing, subchondral sclerosis, osteophyte formation, or femoral head collapse associated with avascular necrosis.