Femoroacetabular impingement (FAI) occurs when extra bone develops along one or both of the bones forming the hip joint, giving them an irregular shape. This abnormal contact between the bones causes friction during movement, damaging the cartilage and labrum over time.

There are two types: cam impingement (extra bone on the femoral head) and pincer impingement (extra bone on the acetabular rim). Many patients have a combination of both (mixed impingement). FAI is common in young, active adults and athletes.

If left untreated, FAI can lead to labral tears and early-onset osteoarthritis. Early diagnosis and appropriate management — including activity modification, physiotherapy, and in some cases arthroscopic surgery — can prevent long-term joint damage.