Hip pain is a notoriously imprecise complaint — patients point to a broad zone from the outer thigh to the groin to the buttock and call all of it "hip pain," when the anatomy generating those symptoms may be completely different in each location. The differentiation that matters most clinically is separating intra-articular hip pathology — disease within the hip joint itself — from extra-articular causes. That distinction determines whether the patient needs an orthopedic hip specialist, a sports medicine evaluation, a spine workup, or a physiatrist focused on the soft-tissue envelope around the joint.
Femoroacetabular Impingement: The Most Underdiagnosed Condition in Active Adults
Femoroacetabular impingement (FAI) is an abnormality in the shape of the femoral head, the acetabular socket, or both, that causes abnormal contact between these two surfaces at the limits of hip range of motion. FAM-type impingement (cam) involves an aspherical femoral head that jams into the acetabulum in flexion. Pincer-type impingement involves over-coverage of the femoral head by the acetabulum. Mixed type — both — is the most common presentation. The consequence of chronic impingement is labral tear and, eventually, articular cartilage damage that progresses to early osteoarthritis.
FAI classically presents in young to middle-aged active adults — often in their 20s and 30s — with anterior groin pain provoked by prolonged sitting, rising from a chair, hip flexion activities, and the specific motion of bringing the knee toward the chest and across the body. Many patients describe a "C-sign" — cupping the lateral hip with the thumb and fingers to indicate the deep, diffuse ache they feel with activity. Morning stiffness that loosens with movement is common.
- Lateral hip or outer thigh aching, worse with prolonged standing or lying on that side
- Buttock pain that improves with walking and worsens after prolonged sitting
- Mild groin pull sensation after a specific athletic exertion that improved quickly
- Full range of motion in the hip without groin pain at end range
- No night pain at rest
- Groin or anterior hip pain with hip flexion that limits daily activity
- Clicking, catching, or sharp stabbing sensation deep in the hip with movement
- Groin pain worse with prolonged sitting and rising from chairs
- Antalgic gait — shortened stride or limp
- Night pain that is non-positional
- Any hip pain in a child or adolescent — proximal femoral physeal problems are age-specific emergencies
The Diagnosis Problem
FAI and labral tears are frequently attributed to "hip flexor tightness" or "piriformis syndrome" for months to years before appropriate imaging establishes the correct diagnosis. Plain radiographs with specific views (AP pelvis, Dunn view, cross-table lateral) are required to assess bony morphology — standard hip X-rays with poor positioning miss the diagnosis. MR arthrography with intra-articular gadolinium contrast provides the most accurate evaluation of labral anatomy and cartilage status, with sensitivity for labral tears exceeding 90% in experienced centers. Standard MRI without arthrogram misses a meaningful percentage of labral pathology.
- Griffin DR, Dickenson EJ, O'Donnell J, et al. The Warwick Agreement on femoroacetabular impingement syndrome (FAI syndrome): an international consensus statement. Br J Sports Med. 2016;50(19):1169–1176.
- Laborie LB, Lehmann TG, Engesæter IØ, et al. Prevalence of radiographic findings thought to be associated with femoroacetabular impingement in a population-based cohort of 2081 healthy young adults. Radiology. 2011;260(2):494–502.
- Philippon MJ, Maxwell RB, Johnston TL, et al. Clinical presentation of femoroacetabular impingement. Knee Surg Sports Traumatol Arthrosc. 2007;15(8):1041–1047.
- Register B, Pennock AT, Ho CP, et al. Prevalence of abnormal hip findings in asymptomatic participants: a prospective, blinded study. Am J Sports Med. 2012;40(12):2720–2724.