:6; Personal non-commercial use only

ABSTRACT. Objective. To determine whether serum markers of bone formation and resorption, used individually or in combination, can be used to identify subgroups who lose cartilage volume at different rates over 2 years within a knee osteoarthritis (OA) population. Methods. Changes in cartilage volume over 2 years were measured in 117 subjects with knee OA using magnetic resonance imaging. We examined relationships between change in cartilage volume and baseline serum markers of bone formation [intact N-terminal propeptide of type I procollagen (PINP) and osteocalcin] and resorption [N-telopeptide of type I collagen (NTX-I), C-telopeptide of type I collagen (CTX-I), and C-telopeptide of type I collagen (ICTP). Results. The baseline markers of bone formation, PINP and osteocalcin (p = 0.02, p = 0.01, respectively), and the baseline markers of bone resorption, CTX-I and NTX-I (p = 0.02 for both), were significantly associated with reduced cartilage loss. There were no significant associations between baseline ratios of bone formation to resorption markers and cartilage loss. However, when subjects were divided into subgroups with high or low bone formation markers (based on levels of marker ≥ mean or < mean for the population, respectively), in the subgroup with high PINP there was a significant association between increasing bone resorption markers CTX-I and NTX-I and reduced cartilage loss (p = 0.02, p = 0.001, respectively). Similarly, in the subgroup with high osteocalcin, there was a significant association between increasing CTX-I and NTX-I and reduced cartilage loss (p = 0.02, p = 0.003, respectively). In contrast, in subgroups with low bone formation markers, no significant associations were obtained between markers of bone resorption and cartilage loss. Conclusion. Overall, the results suggest that higher bone remodeling (i.e., higher serum levels of bone formation and resorption) is associated with reduced cartilage loss. Central and Eastern Clinical School, Alfred Hospital, Melbourne, Victoria 3004, Australia. E-mail: anita.wluka@med.monash.edu.au Accepted for publication January 12, 2010. Osteoarthritis (OA) is a complex disease that affects tissues of the entire joint, including articular cartilage and subchondral bone simultaneously. In those with OA, skeletal size and composition is abnormal, even distant to affected joints 1,2 . Increased osteoblastic activity, demonstrated by bone scans, has been linked to increased progression of knee OA 3 . Recently, the presence of bone marrow lesions, occurring in the subchondral region, has been linked to pain and disease progressio