Cam-type femoroacetabular impingement (FAI) is a major cause of hip osteoarthritis. Quantitative T1ρ MRI has the potential to detect early cartilage degeneration due to its sensitivity to proteoglycan. In this study we performed longitudinally (124 days (average) after surgery and 4.8 years (average) follow up) T1ρ mapping in patients with bilateral (symptomatic and asymptomatic) cam-type FAI on the asymptomatic side after the symptomatic cam-FAI was surgically corrected. The cartilage of the contralateral hip did not show significant proteoglycan depletion and therefore no further degeneration between the initial and the follow up scan was detected. The contralateral hips remained stable.