Hip impingement is diagnosed through a combination of physical exam maneuvers, imaging, and sometimes a diagnostic injection. No single test confirms it on its own. The 2016 Warwick Agreement, the international consensus on femoroacetabular impingement (FAI) syndrome, requires all three elements to be present: symptoms, clinical signs on examination, and imaging findings that show abnormal bone shape.
What Symptoms Point Toward Impingement
The hallmark symptom is pain in the hip or groin that gets worse with certain movements or positions, particularly deep flexion like squatting, sitting for long periods, or pivoting. Some people also feel clicking, catching, locking, or a sense that the hip might give way. Pain can radiate to the back, buttock, or thigh, which is one reason impingement often gets mistaken for other conditions.
A characteristic sign is the “C-sign,” where you instinctively grip the side of your hip just above the bony prominence with your thumb behind and fingers in front, forming a C shape around the joint. If that gesture feels familiar when someone asks where it hurts, it’s a useful clue that the pain originates from inside the hip joint rather than from a tendon or muscle on the surface.
Physical Exam Tests Your Provider Will Use
The most widely used hands-on test is the FADIR maneuver (flexion, adduction, internal rotation). You lie on your back while the examiner bends your hip to 90 degrees, moves the knee across your body, and rotates the shin outward so the thighbone rotates inward. A positive result means this reproduces your typical hip or groin pain. The FADIR test is highly sensitive, meaning it catches most true cases, but it’s not very specific. Plenty of other hip problems also produce pain during this maneuver, so a positive FADIR alone doesn’t seal the diagnosis.
The FABER test (flexion, abduction, external rotation) is often performed alongside FADIR. For this one, you place the ankle of your affected leg just above the opposite knee, letting the hip fall open into a figure-four position. The examiner stabilizes the opposite side of your pelvis and gently presses the bent knee toward the table. Pain in the hip or groin counts as a positive result. Together, the FADIR and FABER give a more complete picture than either test alone.
Internal rotation is typically the most restricted movement. Your examiner will compare both sides with the hip bent to 90 degrees. A noticeable difference, where the affected hip rotates inward significantly less than the other side, is one of the most consistent physical findings. Flexion and abduction may also be limited, though this tends to show up later as the condition progresses.
Testing for Posterior Impingement
Not all impingement happens at the front of the hip. Ischiofemoral impingement occurs at the back, where the thighbone pinches against the sit bone. The provocative test for this involves passively extending and slightly pulling the leg inward (adduction) while rotating it outward. Pain during this maneuver, which resolves when the leg moves into abduction instead, suggests posterior impingement. A long-stride walking test, where you simply take exaggeratedly large steps, also provokes symptoms with about 92% sensitivity and 82% specificity. If your pain is more in the buttock and flares with walking rather than sitting, posterior impingement deserves specific evaluation.
Imaging: X-Rays Come First
A standard evaluation starts with two X-rays: a front-on view of the pelvis and a lateral (side) view of the femoral neck. These reveal the bone shapes that cause impingement. In cam-type impingement, the femoral head isn’t perfectly round, creating a bump that jams against the socket during movement. In pincer-type, the socket rim extends too far over the femoral head. Many people have elements of both.
The key measurement on imaging is the alpha angle, which quantifies how round or misshapen the femoral head is. A commonly used threshold is 55 degrees or above to indicate cam morphology, though more recent evidence suggests 60 degrees is a better cutoff for identifying a true cam deformity. An alpha angle of 78 degrees or higher has been linked to progression toward significant joint damage over time. Normal values vary by sex, with men tending to have slightly higher baseline angles.
One important caveat: abnormal bone shape on imaging doesn’t automatically mean you have FAI syndrome. Many people with cam or pincer morphology on X-ray have no symptoms at all. That’s precisely why the diagnostic criteria require symptoms and exam findings alongside imaging. The bone shape explains the mechanism, but only matters clinically when it’s causing problems.
When MRI or MR Arthrography Is Needed
If X-rays confirm abnormal bone shape and your symptoms and exam are consistent, your provider may order cross-sectional imaging to look at the soft tissue damage impingement causes, particularly labral tears and cartilage injury. This information becomes important when surgery is being considered.
Standard MRI detects labral tears with about 66% sensitivity and 79% specificity. MR arthrography, where contrast dye is injected into the joint before scanning, performs better at roughly 87% sensitivity and 64% specificity. The dye separates the structures inside the joint and makes tears easier to see. A meta-analysis of 19 studies covering 881 hips confirmed that MR arthrography is the superior option overall for detecting labral pathology. If your MRI comes back looking normal but suspicion remains high, MR arthrography is a reasonable next step.
Diagnostic Injections as a Confirmation Tool
When the picture is still unclear, or when your provider wants to confirm that the hip joint itself (rather than a nearby structure) is the true source of pain, a diagnostic injection can help. A numbing agent is injected directly into the hip joint under imaging guidance. You then perform the activities that normally provoke your pain.
A positive response is defined as 75% or greater improvement in pain after the injection. Research shows that patients who meet this threshold go on to have significantly better outcomes after hip arthroscopy compared to those with a weaker response. In other words, the injection serves double duty: it confirms the diagnosis and helps predict whether surgery is likely to help.
Conditions That Mimic Hip Impingement
Groin and hip pain have a long list of possible causes, and several conditions overlap significantly with FAI in how they present. Hip dysplasia, where the socket is too shallow, can cause similar motion-related groin pain. Iliopsoas tendinitis produces front-of-hip pain that worsens with flexion. Greater trochanteric bursitis and gluteal tendinopathy cause pain on the outer hip that can be confused with the C-sign region. Snapping hip syndrome creates audible or palpable clicking that mimics the mechanical symptoms of impingement.
Less obvious mimics include lumbar radiculopathy, where a pinched nerve in the lower back refers pain into the hip or groin, and avascular necrosis of the femoral head, which causes progressive hip pain without a clear mechanical trigger. Even iliotibial band syndrome can be mistaken for hip pathology. This is why the diagnostic process involves layering symptoms, exam findings, and imaging rather than relying on any single piece of evidence. Each step narrows the list until the picture becomes clear.