OBJECTIVE: Changes in biomarkers for bone and cartilage in knee osteoarthritis (KOA) may reflect changes in tissue turnover induced by interventions. The aim of this study was to assess the effect on osteoarthritis biomarkers of an intensive weight loss intervention in obese KOA patients.

METHODS: 192 obese KOA patients followed a 16 weeks weight loss intervention (ClinicalTrials.gov: NCT00655941). Serum Cartilage Oligomeric Matrix Protein (sCOMP), Urine C-terminal telopeptide of collagen type II (uCTX-II) and type I (uCTX-I) were determined by enzyme-linked immunoassay (ELISA) at baseline and after 16 weeks. Patient-reported symptoms were assessed by the Knee Injury and Osteoarthritis Outcome Score (KOOS) Questionnaire without the sports and recreation score (KOOS-4). Change from baseline was analyzed using Analysis of CoVariance (ANCOVA) adjusting for sex, age, and body mass index (BMI). Bivariate associations were analyzed using Spearman's test of rank correlation.

RESULTS: 175 patients completed the treatment and lost mean 13.4 (95% CI: 12.5-14.4) kg. sCOMP concentration decreased on average 1.1 (95% CI: -1.5 to -0.8) U/L with a correlation to weight loss (r = -0.17, P = 0.028), but not to change in KOOS-4 (r = -0.13, P = 0.091). uCTX-II increased significantly, mean 69 (95% CI: 31-106) ng/mmol creatinine, with no relation to weight loss (P = 0.14). Change in uCTX-II was reversely related to change in KOOS-4 (r = -0.28, P = 0.0003). uCTX-I increased, mean 67 (95% CI: 47-87) μg/mmol creatinine, and correlated to weight loss (r = 0.22, P = 0.0007), while not to KOOS-4 (P = 0.93).

CONCLUSION: A rapid substantial weight loss in obese KOA patients was weakly, while significantly associated with a reduction in sCOMP, and increases in both uCTX-II and uCTX-I.