How Cam Morphology and FAI Syndrome Lead to Hip Osteoarthritis

Cam morphology is forced into the anterosuperior acetabulum during flexion and internal rotation, where it can peel cartilage off the subchondral bone in a carpet lesion. Prospective cohorts show a 2 to 9 times higher risk of hip osteoarthritis with cam morphology, but positive predictive values of only 6% to 25%, so cam morphology on imaging alone is treated as a normal shape variant. In a Dutch cohort of 1,000 people aged 45 to 65 with first onset hip or knee pain, only 21 hips met criteria for FAI syndrome. Over ten years these hips had a 26 times higher risk of osteoarthritis, with a positive predictive value of 33%. In the younger FORCe cohort, cartilage lesions were found in 17% of hips without cam morphology, 40% with alpha angles of 60 to 78 degrees and 57% above 78 degrees. Young Feyenoord players with cam morphology were 4.5 times more likely to have cartilage lesions 12 years later. Rintje closes on cam-type FAI as a syndrome that mainly predisposes the hip to later osteoarthritis.