Summary Objective To evaluate the longitudinal reproducibility and variations of cartilage T1ρ and T2 measurements using different coils, MR systems and sites. Methods Single-Site study : Phantom data were collected monthly for up to 29 months on four GE 3T MR systems. Data from phantoms and human subjects were collected on two MR systems using the same model of coil; and were collected on one MR system using two models of coils. Multi-site study: Three participating sites used the same model of MR systems and coils, and identical imaging protocols. Phantom data were collected monthly. Human subjects were scanned and rescanned on the same day at each site. Two traveling human subjects were scanned at all three sites. Results Single-Site Study : The phantom longitudinal RMS-CVs ranged from 1.8% to 2.7% for T1ρ and 1.8–2.8% for T2 . Significant differences were found in T1ρ and T2 values using different MR systems and coils. Multi-Site Study: The phantom longitudinal RMS-CVs ranged from 1.3% to 2.6% for T1ρ and 1.2–2.7% for T2 . Across three sites ( n  = 16), the in vivo scan-rescan RMS-CV was 3.1% and 4.0% for T1ρ and T2 , respectively. Phantom T1ρ and T2 values were significantly different between three sites but highly correlated ( R  > 0.99). No significant difference was found in T1ρ and T2 values of traveling controls, with cross-site RMS-CV as 4.9% and 4.4% for T1ρ and T2 , respectively. Conclusion With careful quality control and cross-calibration, quantitative MRI can be readily applied in multi-site studies and clinical trials for evaluating cartilage degeneration.