Overview
The hip is a ball-and-socket joint: the femoral head sits in the acetabulum, and a ring of fibrocartilage called the labrum rims and seals the socket. Femoroacetabular impingement (FAI) is a shape problem: the ball carries a bump at the head-neck junction (cam), the socket covers too much of the ball (pincer), or both. Every deep bend presses the bump against the rim, and over thousands of squats and pivots that contact shears the labrum and peels cartilage off the socket edge.
The shape is common and present in many hips that never hurt. Treatment is decided by three things: whether the impingement is producing the pain, whether the cartilage is still healthy, and whether a proper course of rehabilitation has failed.
Common Symptoms
- Deep groin pain with squatting, lunging, low chairs or getting out of a car — patients often cup the side of the hip in a “C” to show where it hurts
- Aching after prolonged sitting or driving
- Loss of rotation: difficulty putting on a sock, or a knee that turns inward less than the other side
- Pain with pivoting, cutting or deep flexion in hockey, soccer, martial arts, dance or rowing
- Clicking or catching, which usually means the labrum has torn
Groin pain with deep flexion is the typical presentation. Outer-hip pain that hurts to lie on points to greater trochanteric bursitis; groin pain with a limp and morning stiffness after 50 points to hip arthritis; catching usually means a labral tear, which in most cases is the consequence of impingement rather than a separate problem.
Causes & Risk Factors
The cam shape develops in adolescence. Heavy loading of the growth plate at the top of the femur during the teenage years — year-round hockey, soccer, basketball and football are the classic sports — reshapes the head-neck junction, so cam impingement is most common in young men who trained hard through puberty. Pincer over-coverage is somewhat more common in women. Neither is caused by a single injury. Symptoms usually start in the 20s and 30s; a symptomatic cam hip can progress to early arthritis by the mid-40s, although most hips with the shape never do.
How It Is Diagnosed
Dr. O'Donnell measures rotation with the hip flexed to 90° — internal rotation under about 20° is typical of a cam hip — and performs the FADIR test (flexion, adduction and internal rotation), which reproduces groin pain by driving the bump into the rim. The FABER test, log roll and a resisted straight-leg raise separate joint pain from muscle, tendon or spine sources.
An AP pelvis and a Dunn lateral X-ray show the shape: the alpha angle quantifies a cam bump (over about 55° is abnormal), the crossover sign and center-edge angle show pincer over-coverage, and the joint space shows whether cartilage remains. Those two films decide more than the MRI does. MRI with contrast injected into the joint shows the labrum and cartilage and is ordered once surgery is a possibility. An ultrasound-guided anesthetic injection that abolishes the pain for a few hours confirms the joint as the source. Out-of-town patients can upload imaging through mymedicalimages.com.
Imaging Findings in People Without Symptoms
The bone shapes linked to hip impingement, a bump on the ball (cam) or a deep rim on the socket (pincer), are common in hips that have never hurt. In large studies of young adults with no hip pain, more than one in three had a cam shape, and it was more common still in athletes. When pain-free hips with these shapes were followed for nearly twenty years, most never developed arthritis.
Dr. O'Donnell separates an impingement shape from impingement syndrome, and diagnoses the syndrome only when three things agree. The story has to be groin pain with deep bending, squatting or pivoting. The examination has to reproduce that pain when the hip is flexed and turned inward, with the spine and the outer hip tendons checked so their pain is not blamed on the joint. The X-rays have to show the shape on the painful side. When the source is uncertain, a numbing injection into the joint that stops the pain confirms it, and a hip that settles with six to twelve weeks of rehabilitation is not operated on, whatever its shape.
A cam or pincer shape on an X-ray or MRI is not by itself a diagnosis of hip impingement, and it is not by itself a reason for surgery. Most people with the shape never need an operation.
Treatment Options
Non-operative care
Everyone starts here. The program runs 6 to 12 weeks: avoid the positions that pinch (deep squats, low seats, prolonged sitting, deep yoga hip openers), and work with a physical therapist on gluteal and core strength and pelvic control so the joint is loaded mid-range rather than at the end. A short course of anti-inflammatories and an ultrasound-guided corticosteroid injection into the joint can settle an irritable hip enough to let therapy work. Rehabilitation does not change the bone, but a substantial share of patients become comfortable enough to keep playing.
Hip arthroscopy
When groin pain persists after a real course of rehabilitation, the impingement tests are positive, the X-rays show a cam or pincer shape and the joint space is preserved, Dr. O'Donnell recommends hip arthroscopy. The cam bump is reshaped (femoroplasty), an over-covering rim is trimmed (acetabuloplasty), the labrum is repaired to the rim with suture anchors, and the capsule is closed. Correcting the bone is the point; repairing the labrum without removing the cause is why earlier hip arthroscopy failed. The surgery is outpatient at Bayside Surgery Center under a nerve block and general anesthesia. It is not offered when the joint space is under about 2 mm, because arthroscopy does not help an arthritic hip, and it is not the right operation for a shallow, dysplastic socket.
Recovery & What to Expect
Without surgery, most patients know within 6 to 12 weeks whether rehabilitation will be enough. After arthroscopy, every phase of Dr. O'Donnell's protocol is advanced on criteria rather than elapsed time.
| Phase | Timing | What happens |
|---|---|---|
| Protection & motion | Weeks 0–3 | Flat-foot partial weight bearing on crutches (about 20 lb). No active hip flexion past 90°, no extension with external rotation. Passive motion, high-seat bike without resistance, isometrics. |
| Progressive motion & load | Weeks 3–6 | Wean crutches; restore full motion while avoiding pinch positions. Mini-squats, bridges, balance. No pivoting or aggressive stretching until 6 weeks. |
| Strengthening | Weeks 6–12 | Progressive hip and core resistance, single-leg strength, elliptical. Light jogging late in the phase if strength reaches 80% of the other side. |
| Return to sport | Months 3–6 | Running, then agility, cutting and plyometrics. Cleared on symmetric strength and functional testing, typically at 4 to 6 months. |
Desk work is realistic within 1 to 2 weeks on crutches; driving waits until you are off crutches and narcotic pain medication, usually about 3 weeks. After a microfracture, weight bearing is protected longer. Full details are in the hip arthroscopy protocol PDF.
Frequently Asked Questions
Can femoroacetabular impingement go away on its own?
The bone shape is permanent, but the pain often is not. With 6 to 12 weeks of activity modification and therapy that builds gluteal and core control, many patients settle and stay comfortable. Surgery is reserved for hips that keep hurting after that.
My X-ray shows a cam deformity. Does that mean I need surgery?
No. More than one in three young adults with no hip pain have a cam shape, and most pain-free hips with that shape never develop arthritis. Dr. O'Donnell recommends arthroscopy only when groin pain matches the shape, the examination reproduces it, the joint space is preserved, and six to twelve weeks of rehabilitation has not worked.
Does FAI lead to hip arthritis?
Cam impingement is a recognized cause of hip arthritis before 60, because the bump shears cartilage off the socket rim with every deep bend. Most hips with the shape do not become arthritic: of 96 asymptomatic hips with impingement morphology followed for a mean of 18.5 years, 82% never developed arthritis. Reshaping the bone in a painful hip while the cartilage is still healthy is intended to interrupt that process.
Do I need surgery for hip impingement?
Only if rehabilitation has failed. Dr. O'Donnell recommends hip arthroscopy when groin pain persists after a proper course of therapy, the exam reproduces the pain, X-rays show the cam or pincer shape, and the joint space is preserved. If the X-ray already shows arthritis, arthroscopy is not helpful.
How long is recovery after hip arthroscopy for FAI?
Crutches for 2 to 3 weeks, full motion and normal walking by 6 weeks, strengthening through 12 weeks, jogging around 3 months and pivoting sport at 4 to 6 months once strength is symmetric and functional testing is passed. A microfracture or a large labral repair slows the early weeks.
Can I keep running or lifting with FAI?
Straight-line running in the middle of the hip's range is usually tolerated. Deep squats, heavy lunges, low seats and deep hip-opening stretches are the positions that pinch and should be cut back while the hip is irritable. Modifying depth rather than stopping altogether is the usual advice.
This page is for general education and is not a substitute for a medical evaluation. Treatment recommendations depend on your individual diagnosis and goals. Kevin O'Donnell, MD sees patients from Coral Gables, Miami, Brickell, Pinecrest and Coconut Grove at 475 Biltmore Way, and out-of-town patients by telemedicine.