Femoroacetabular Impingement (Hip Impingement): the Hidden Cause of Groin Pain in Young Adults

Hip impingement, medically known as femoroacetabular impingement (FAI), occurs when a mismatch in shape between the ball (femoral head) and socket (acetabulum) of the hip joint causes the bones to abut one another during movement. It is one of the most common structural causes of groin pain in young, active adults, particularly athletes, and can go undiagnosed for years, dismissed as a "groin strain" or a "hernia."

Types

• Cam type: an excess of bone at the junction of the femoral head and neck; when the hip is flexed, this bump damages the cartilage at the socket rim. More common in young male athletes

• Pincer type: the socket (acetabulum) covers the femoral head more than it should, pinching the labrum (the rim cartilage). More common in middle-aged women

• Combined type: the most common form, in which both features occur together

These bone shapes are quite common in the general population; finding them on imaging does not, by itself, mean disease is present. A diagnosis of FAI syndrome requires symptoms, examination findings, and imaging findings together.

Symptoms

• Deep pain in the groin, sometimes on the outer or back side of the hip; patients often describe the location by cupping their hand in a "C" shape around the hip

• Pain with prolonged sitting, getting out of a car, squatting, sitting cross-legged, and tying shoes

• In sport: pain with changing direction, kicking, or deep squatting

• A catching, clicking, or locking sensation in the hip, when a labral tear is present

• Progressive loss of motion, particularly internal rotation

Diagnosis

On examination, pain reproduced by flexing and internally rotating the hip (the FADIR test) is characteristic. Hip X-rays taken at specific angles show the bone shape. MRI, and especially MR arthrography (MRI with contrast injected into the joint), demonstrates labral tears and cartilage damage. Not every labral tear seen on imaging is a source of pain; a diagnostic injection can confirm that the pain originates from within the joint.

Why Does It Matter?

Repeated impingement leads to progressive damage to the labrum and cartilage at the socket rim. Cam-type FAI is a known risk factor for developing hip osteoarthritis at a young age. Early diagnosis and appropriate treatment can slow this process.

Treatment

Non-Surgical Treatment (First-Line)

• Activity modification: limiting deep squatting and movements requiring excessive flexion

• Physical therapy: strengthening the muscles around the hip and trunk, correcting movement patterns, for at least 3 months

• Short-term anti-inflammatory pain relievers

• Intra-articular injection: for both diagnosis and temporary relief

Arthroscopic Surgery

In patients who do not respond to 3–6 months of non-surgical treatment, hip arthroscopy is used to shave the excess bone (osteoplasty), repair the torn labrum where possible, and treat any cartilage damage. High-quality studies have shown that in appropriately selected patients, arthroscopy produces better outcomes than physical therapy alone. The most important factors for success are age, the extent of cartilage damage, and whether joint space is preserved; arthroscopy is not recommended in patients with advanced cartilage loss.

After Surgery

• 2–4 weeks of partial weight-bearing with crutches

• Early range-of-motion work and prevention of adhesions

• Strengthening from weeks 6–12

• Running at month 3–4; return to sport typically at month 4–6

Frequently Asked Questions

Will a labral tear heal on its own? The labrum has a poor blood supply, so a tear does not heal on its own — but not every tear causes symptoms or requires treatment.

Does surgery definitively prevent osteoarthritis? Long-term data on this are not yet conclusive; surgery improves pain and function and is expected to slow cartilage damage, but there is not yet sufficient evidence that it prevents it entirely.

This article is for general information purposes; a personal examination is required for an individual treatment plan.