Knee cartilage defects in a sample of older adults: natural history, clinical significance and factors influencing change over 2.9 years.

OBJECTIVE: To describe the natural history of knee cartilage defects, and their relationship to cartilage volume loss and risk of knee replacement in a longitudinal study of older adults.
DESIGN: 395 randomly selected older adults (mean age 62.7 years) had magnetic resonance imaging of their right knee at baseline and approximately 2.9 years later to determine cartilage defect grade (0-4), cartilage volume, medial and lateral tibial bone size, and presence of bone marrow lesions (BMLs). Height, weight, body mass index (BMI) and radiographic osteoarthritis were measured by standard protocols.
RESULTS: At baseline higher grade cartilage defects (grade ≥2) were significantly associated with age, BMI, lateral tibial bone size, BMLs, and radiographic osteoarthritis. Over 2.9 years, the average defect score increased statistically significantly in all compartments; however, the majority of defects remained stable and regression of defects was rare. Baseline factors associated with increase in defect score over 2.9 years were radiographic osteoarthritis, tibial bone size, BMI and being female. In multivariate analysis, baseline cartilage defect grade predicted cartilage volume loss at the medial tibia, lateral tibia and patella over 2.9 years (β = -1.78% to -1.27% per annum per 1 grade increase, P < 0.05 for all comparisons), and risk of knee replacement over 5 years (odds ratio (OR) = 1.73 per 1 grade increase, P = 0.001).
CONCLUSION: Knee cartilage defects in older adults are common but less likely to regress than in younger life. They independently predict cartilage volume loss and risk of knee replacement, suggesting they are potential targets for intervention.