Medial femur T2 Z-scores predict the probability of knee structural worsening over 4-8 years: Data from the osteoarthritis initiative.

OBJECTIVE: The purpose of this study was to determine the probability of structural worsening of knee cartilage and whole joint degeneration over 4-8 years based on cartilage T2 Z-scores at baseline.
DESIGN: Right knees with Kellgren-Lawrence (KL) grades of 0-2 in 587 participants from the Osteoarthritis Initiative were studied. 3T MR images were used to perform baseline cartilage T2 quantification and assess 4-year changes in cartilage morphology (WORMS scoring) in 5 regions. Changes in joint space narrowing (JSN) and KL were assessed over 8 years. T2 Z-scores were based on a reference database of knees without morphologic cartilage degeneration at baseline. Odds ratios for, and predicted probabilities of any worsening in WORMS cartilage, JSN and KL grade were obtained from logistic regression models.
RESULTS: A one-unit increase in the baseline medial femur T2 Z-score was associated with cartilage worsening in the same region (OR = 1.59; P < 0.0001) and in any region (OR = 1.37; P < 0.0001), and with worsening JSN (OR = 1.82; P < 0.0001) and KL grades (OR = 1.69; P < 0.0001). Predicted probabilities of worsening in knees with a medial femur T2 Z-score from 2-4 were 38% for medial femur cartilage WORMS, 70% for any cartilage region, 28% for increasing JSN and 31% for increasing KL grade.
CONCLUSION: Knees with elevated cartilage T2 (especially in the medial femur and those that are 2 to 4 SDs above the mean reference values) are significantly more likely to have structural worsening over 4 to 8 years. Knowing cartilage T2 Z-scores may aid in targeting prevention efforts at early stages of osteoarthritis. LEVEL OF EVIDENCE: 2 Technical Efficacy: Stage 3 J. Magn. Reson. Imaging 2017;46:1128-1136.