The underlying bony morphology associated with femoroacetabular impingement (FAI) subjects the joint to mechanical wear that predisposes young, active individuals to early osteoarthritis and chronic pain.1,2 Repetitive articulation between an abnormally shaped femur and/or acetabulum may tear the labrum and delaminate cartilage at the chondrolabral junction; osteoarthritis develops as articular cartilage continues to deteriorate.
The structural malformations associated with FAI are believed to be congenital or developmental, as the bone undergoes periods of rapid remodeling when subjected to vigorous activity throughout adolescence.3 Although FAI is thought to develop throughout skeletal maturation, clinically relevant symptoms may not manifest for several years, if ever. Because bony anatomy tends to develop symmetrically, a patient with radiographic signs of FAI on one side might be expected to demonstrate similar findings on the contralateral hip. However, not all patients with FAI will present with bilateral symptoms; the pathophysiologic explanation for this phenomenon remains to be explored, although injury or hip dominancy may play a role.1
Although some patients present with a sudden onset of symptoms in response to a traumatic insult, the more common presentation is insidious hip pain as a result of formation of excess bone at the femoral head-neck junction and rim of the acetabulum.
Two types of FAI are recognized, although most patients have a combination of these types and are categorized as mixed.
Cam deformity or cam impingement is an osseous deformity caused by a growth abnormality in the femoral capital epiphysis, and is most commonly detected in young, athletic men.4 This “bump” generally forms in the anterosuperior or lateral portion of the femoral head-neck junction and can be further attributed to a multitude of disease processes and structural abnormalities (Figure 1).
Pincer deformity, located on the acetabular side, is caused by excessive coverage of the femoral head and is more common in middle-aged women who participate in activities requiring an extreme range of motion, such as dance, tumbling, or hurdling (Figure 2).1
Both forms of FAI present with a similar patient history and physical examination and contribute significantly to gradual arthritic changes within the hip joint. Secondary bony changes and soft tissue damage are more common with cam deformities, which result from the aspherical femoral head forcing its way into a round socket. Patients with either deformity who are asymptomatic or only minimally bothered at the time of diagnosis should continue to monitor symptoms diligently. To avoid irreparable damage to the articular cartilage, patients should seek surgical evaluation promptly if their condition changes or continues to worsen.
HISTORY AND PHYSICAL EXAMINATION
The clinical diagnosis of FAI can be challenging—patients often present with unilateral hip pain but have similar bony morphology on the contralateral side. In other patients, imaging studies may reveal findings consistent with FAI but the patient reports back, pelvic, hip, or groin pain suggestive of an entirely different diagnosis. Despite its variable presentation, five core elements are essential to making a diagnosis of authentic FAI:
- abnormal morphology of the femoral head/neck and/or acetabulum
- mechanical contact between these bony elements
- vigorous motion throughout the three-dimensional plane of contact
- continuous insult due to repetitive motion
- soft-tissue damage to the labrum and/or articular cartilage.2
Though neither clinical hip symptoms nor physical examination findings are among these criteria, they can help determine appropriate treatment. Additional guidelines have been established so that, when coupled with a targeted history, appropriate physical examination, and a high index of suspicion, FAI can be successfully diagnosed (Table 1).
FAI is not an exclusive condition; many activities can cause hip pain, and the patient population can be diverse. However, classically, the presentation of FAI is fairly consistent. Patients experiencing hip pain due to FAI are typically in their 20s to 40s, and men and women are equally affected.5 Traditionally, patients are active in recreational or occupational activities that require deep flexion or an extreme range of motion; for example, dancers, gymnasts, cyclists, and football, hockey, and soccer players.
More sedentary patients, such as those whose jobs involve prolonged periods of sitting or standing, or those who participate in low-resistance activities such as yoga, may present once the joint irritation and inflammation has progressed to the point of affecting daily activities such as walking or climbing stairs. These patients may have constant pain that intensifies with activity and may be positional in nature.
Most patients, whether sedentary or active, will complain of deep groin pain, occasionally accompanied by mechanical symptoms such as popping, clicking, and catching that is mostly activity-related but that may evolve to include simple tasks such as sitting and squatting. Other frequently noted pain distributions include the lower back, buttock, and thigh; the ipsilateral knee and/or the contralateral hip may suffer due to postural compensation. Straight plane or inline activities are relatively well tolerated, but torsional or pivoting movements become more problematic.
Obtain a detailed history, including a thorough review of sports and daily activities that exacerbate symptoms as well as any previous treatments such as conservative measures, diagnostic studies, and prior surgical attempts. Document any history of congenital malformations and musculoskeletal disease, especially in children.
When asked to describe the location of pain, many patients point with one finger to the groin. Other patients may demonstrate the C-sign, cupping a hand above and around the greater trochanter with the thumb pressing the posterior aspect of the trochanter and the fingers gripping the groin. This gesture, highly suggestive of intra-articular hip pathology, is also fairly common in patients with acetabular dysplasia, or a shallow acetabulum. In addition, patients with FAI often present with postural changes, such as slouching while seated, in an effort to minimize the degree of flexion on the affected side.
Physical assessment involves gait evaluation (including type of limp and weight-bearing status of the affected side), palpation of the hip and surrounding area, examination of range of motion, and diagnostic testing. Patients with FAI typically have a normal gait pattern; an antalgic or Trendelenburg gait (lateral lurch) may be detectable only occasionally or if the patient has sustained acute hip trauma.5,6 Significant leg-length discrepancies (differences greater than 1 cm) should be identified. Palpation of the anterior superior iliac crest, groin, and greater trochanter usually is unremarkable. Provocative testing is the most sensitive portion of the examination and should include testing for anterior impingement, flexion/adduction/internal rotation, and flexion/abduction/external rotation (Table 1). The anterior impingement test will reveal remarkably limited internal rotation and should re-create, or nearly reproduce, the identical character and location of pain as does the chief complaint (Figure 3). Additional tests may be helpful in excluding alternative or secondary diagnoses (Table 2). Perform a cursory examination of the patient's lower back, ipsilateral knee, and contralateral hip to rule out concomitant pathology.
Diagnosing FAI is complex. Pelvic pain can be caused by musculoskeletal, genitourinary, gastrointestinal, gynecologic, or neurovascular issues. The differential diagnosis for hip pain is vastly diverse, consisting of intra-articular and extra-articular pathologies, as well as systemic diseases that may closely mimic the seemingly straightforward hip pain likened to FAI (Table 3).
Viewing the differential from a purely anatomic standpoint is one method of ensuring the patient receives a thorough and methodical examination. One approach is to establish whether the source of hip pain is intra-articular or extra-articular. In addition, the ability to differentiate pain that arises from surrounding musculature from true bone or joint pain is oftentimes very helpful in determining whether conservative treatment (such as physical therapy) or surgical intervention is indicated.
Among extra-articular pathologies, the painful groin is perhaps the most tenuous to diagnose. Despite evidence that suggests strains represent the most common cause of groin pain, among athletes as great as 60% of intra-articular disorders may be initially misdiagnosed as extra-articular complications.7 Classic hernias (inguinal hernias with a palpable bulge), occult groin injuries (including athletic pubalgia [sports hernia] and osteitis pubis), and strains are considered to be major diagnostic groups of musculoskeletal groin disorders.8 Adductor injuries—more commonly the adductor brevis and adductor longus and less commonly the gracilis and pectineus—also are frequently treated.8 Because these findings are all associated with repetitive hip abduction and extension, aggressive movement, rapid acceleration-deceleration, and quick lateral cutting movements, clinicians should not assume that they are the sole cause of pain—acute labral tears share the same mechanisms of injury.
Peritrochanteric space disorders consist of pathological conditions within the space between the greater trochanter and the iliotibial band (an area analogous to the subacromial space within the structure of the shoulder) and include external snapping hip, recalcitrant trochanteric bursitis, and abductor injuries of the gluteus medius or gluteus minimus.9 Greater trochanteric pain syndrome, formerly called trochanteric bursitis, manifests as lateral-sided hip pain with painful symptoms that are commonly reproducible with direct palpation of the greater trochanter. Symptoms of external snapping hip, or iliotibial band syndrome, develop as a result of either a tight or weak iliotibial band that slips over the greater trochanteric bursa when the hip is brought into flexion. Movement of internal structures under the skin “can be seen from across the room.” Slipping of the iliotibial band may create a dislocating sensation, eliciting pain laterally over the greater trochanter that can radiate down the lateral aspect of the thigh and into the buttock.10
Conversely, internal snapping hip syndrome may be due to intra-articular pathology, or might simply be attributed to overuse, and the clunking sound “can be heard from across the room.” Pain with internal snapping hip is often described as anterior groin pain or pain that radiates to the anteromedial thigh or even to the ipsilateral knee.10 The mechanical symptoms of both external and internal snapping hip are easily reproducible on examination. Recognize that many patients with internal or external snapping hip syndromes report that, though bothersome, the mechanical findings of these diagnoses do not re-create the same sensation of hip pain as the chief complaint, if true FAI is the underlying pathology. Lastly, hamstring injuries are among the most common sports injuries; differentiation between a strain and an avulsion is critical.
Intra-articular pathology is the strongest indication for hip surgery and includes diagnoses such as capsular instability, articular trauma, loose body, acute or degenerative damage to the labrum or ligamentum teres, synovial disorders, degenerative disease, and osteonecrosis. Capsular instability in the posterior direction traditionally occurs with macrotrauma related to dashboard injuries or high-impact sports contact and is usually accompanied by a labral tear. On the other hand, laxity in the anterior direction is typically atraumatic in nature and may be attributed to repetitive microtrauma or collagen vascular disorders such as Ehlers-Danlos syndrome.11 Articular trauma also may be acute or degenerative and could potentially result in a loose body detectable on first-line imaging studies. Synovial disease is identified as either focal or diffuse. If intra-articular pathology is the cause of pain, consider inflammatory arthritides (such as rheumatoid arthritis), pigmented villonodular synovitis, chondromatosis, or chemically induced and nonspecific synovial pathology.11
Other conditions can degrade or compromise the bony integrity within the joint. Osteonecrosis, whether due to idiopathic or avascular causes, and bone marrow edema syndrome (transient osteoporosis or transient marrow edema syndrome), a self-limiting skeletal disease, have both been found to localize most commonly to the hip joint.12
The sequelae of pediatric hip diseases such as Legg-Calvé-Perthes disease (idiopathic osteonecrosis of the femoral capital epiphysis) and slipped capital femoral epiphysis predispose patients to FAI based on inherent characteristics of bony malformation.4
Developmental dysplasia of the hip, also called acetabular dysplasia, is a congenital or developmental abnormality of the hip that ultimately results in a deficient acetabulum (shallow socket). The presentation is most often confused with FAI. On plain radiographs, developmental dysplasia of the hip presents as inadequate coverage of the femoral head by the weight-bearing dome, or sourcil, of the acetabulum (Figure 4). Ideally, dysplastic hips are identified at newborn and well-baby examinations, but an increasing number of patients develop symptoms between their late teenage years and their 40s. Like patients with FAI, those with dysplasia also commonly experience referred deep groin pain. Yet, unlike FAI, patients with developmental dysplasia of the hip complain of occasional instability, and lateral-sided muscle fatigue with endurance-type activity, such as running or walking long distances. These patients generally do not have tenderness over the greater trochanter and their physical examination may reveal excessive femoral anteversion, with greater internal rotation than external rotation of the hip. Patients with dysplasia also may sustain a torn labrum after a traumatic injury, compounding the presentation and further emphasizing the need to collect an accurate history and perform a careful review of diagnostic imaging.
For evaluation of FAI, anteroposterior (AP) pelvis, frog-lateral (some prefer cross-table lateral or the Dunn view), and false-profile radiographic views are sufficient. As with any imaging study, malalignment of patient position and equipment may result in perceived pelvic tilt or rotation that will ultimately affect the interpretation of the underlying deformity. Remember that FAI may exist (despite minimal evidence of radiologic deformity) in patients with ligamentous laxity who participate in deep hip flexion activities or supraphysiologic motion, such as ballet. Identify signs of moderate-to-severe osteoarthritis of the hip, fractures, and significant lumbar pathology. Advanced imaging modalities such as MRI or CT scan of the hip may be used to further diagnose the source of ambiguous hip pain or to evaluate patients for surgery. Magnetic resonance arthrogram with a diagnostic injection of cortisone and a local anesthetic is potentially helpful in differentiating intra-articular from extra-articular pathology.
For some patients, a period of conservative management, including rest, activity modification, and athletic restrictions that limit deep flexion, and over-the-counter anti-inflammatory drugs, is appropriate. Other patients require more intensive measures, such as physical therapy or intra-articular corticosteroid injections. Patients also may achieve adequate relief with an occasional focused physical therapy program that targets core exercises and lower extremity muscle balance, stabilization, and strengthening. However, the success of physical therapy alone is limited by the patient's bony anatomy, which remains unchanged. For patients who have failed to improve after at least 3 months of conservative measures, referral to an orthopedic provider for surgical intervention may be indicated. Physical examination and imaging alone are insufficient to warrant surgical management; the ultimate indications for surgery depend on the limitations to the patient's daily activities and the patient's scope of preferred activities. Given that 10% to 15% of young adults in their 20s to 40s experience symptoms of FAI, and the correlation between FAI and the development of early hip osteoarthritis, proper evaluation and treatment of this highly prevalent hip deformity is imperative.1
2. Sankar WN, Nevitt M, Parvizi J, et al. Femoroacetabular impingement
: defining the condition and its role in the pathophysiology of osteoarthritis
. J Am Acad Orthop Surg
. 2013;21(suppl 1):S7–S15.
3. Siebenrock KA, Ferner F, Noble PC, et al.The cam-type deformity of the proximal femur arises in childhood in response to vigorous sporting activity. Clin Orthop Relat Res. 2011;469(11):3229–3240.
4. Millis MB, Lewis CL, Schoenecker PL, Clohisy JC. Legg-Calvé-Perthes disease and slipped capital femoral epiphysis: major developmental causes of femoroacetabular impingement
. J Am Acad Orthop Surg
. 2013;21(suppl 1):S59–S63.
5. Peters CL, Erickson JA, Anderson L, et al. Hip-preserving surgery: understanding complex pathomorphology. J Bone Joint Surg Am
. 2009;91(suppl 6):42–58.
6. Nepple JJ, Prather H, Trousdale RT, et al. Clinical diagnosis of femoroacetabular impingement
. J Am Acad Orthop Surg
. 2013;21(suppl 1):S16–S19.
7. Byrd JW, Jones KS. Hip arthroscopy in athletes. Clin Sports Med
8. Gerhardt MB. The painful groin: athletic pubalgia, osteitis pubis and adductor injuries. Presentation. American Orthopaedic Society for Sports Medicine annual meeting, Orlando, FL, 2008.
9. Kelly BT. Non-articular disorders of the hip: evaluation and management of peritrochanteric space disorders. Presentation. American Orthopaedic Society for Sports Medicine annual meeting, Orlando, FL, 2008.
10. Safran MR. Snapping hip syndromes and hamstring injuries. Presentation. American Orthopaedic Society for Sports Medicine annual meeting, Orlando, FL, 2008.
11. Byrd JWT. Intraarticular injuries. Presentation. American Orthopaedic Society for Sports Medicine annual meeting, Orlando, FL, 2008.
12. Orth P, Anagnostakos K. Coagulation abnormalities in osteonecrosis and bone marrow edema syndrome. Orthopedics
Keywords:Copyright © 2015 American Academy of Physician Assistants
hip pain; young adults; femoroacetabular impingement; osteoarthritis; cam deformity; pincer deformity