Osteoarthritis, magnetic resonance imaging, and biochemical markers: a one year prospective study

Objective: To investigate the relation between biochemical markers of bone, cartilage, and synovial remodelling and the structural progression of knee osteoarthritis. Methods: 62 patients of both sexes with knee osteoarthritis were followed prospectively for one year. From magnetic resonance imaging ( MRI), done at baseline and after one year, the volume and thickness of cartilage of the femur, the medial tibia, and the lateral tibia were assessed. A whole organ magnetic resonance imaging score ( WORMS) of the knee was calculated for each patient at baseline and at the one year visits. This score consists in a validated, semiquantitative scoring system for whole organ assessment of the knee in osteoarthritis using MRI. Biochemical markers ( serum hyaluronic acid, osteocalcin, cartilage glycoprotein 39 ( YKL-40), cartilage oligomeric matrix protein ( COMP), and C-telopeptide of type I collagen ( CTX-I), and urine C-telopeptide of type II collagen ( CTX-II)) were measured at baseline and after three months. Results: Baseline markers were not correlated with one year changes observed in cartilage volume and thickness. However, an increase in CTX-II after three months was significantly correlated with a one year decrease in mean thickness of medial tibial and lateral tibial cartilage. Patients in the highest quartile of three month changes in CTX-II experienced a mean loss of 0.07 ( 0.08) mm of their medial thickness, compared with a mean increase of 0.05 ( 0.19) mm for patients in the lowest quartile ( p = 0.04) Multiple regression analysis showed that high baseline levels of hyaluronic acid are predictive of a worsening in WORMS ( p = 0.004). Conclusions: These results suggest that a single measurement of serum hyaluronic acid or short term changes in urine CTX-II could identify patients at greatest risk of progression of osteoarthritis.