INCREASED FRICTION OF ANIMAL JOINTS BY EXPERIMENTAL DEGENERATION AND RECOVERY BY ADDITION OF HYALURONIC-ACID

Objective. To investigate the lubricating ability in osteoarthritic (O A) stifle joints. Design. An experimental study in rabbit stifles in v itro. Background. The lubricating ability in OA joints, and the effect s of the application of hyaluronic acid (HA), a drug for OA, to the os teoarthritic joints have not yet been reported. Methods. The friction in OA stifles induced by two different methods, the intra-articular in jection of papain, and transection of the anterior cruciate ligament ( ACL) was measured using a robotic arm under force control. Results. Th e frictional coefficient in the papain-injected model, that caused sli ght degeneration in the articular cartilage, was 1.3 to 1.8 times as l arge as that in the contralateral uninjected stifles. The elevated val ues decreased significantly by addition of HA to the articular surface (P<0.05). In another group (n = 4), the frictional coefficient in the stifle at 9 months after ACL transection that caused severe degenerat ion in the articular cartilage was 1.6 to 7.8 times as large as that i n the contralateral unoperated stifle. The addition of HA decreased th e elevated values in three of the four ACL-transected joints. Conclusi on. Friction was higher in the OA joints than in the healthy joints. T he addition of HA was effective in the early stage of OA represented b y papain injected case, while its effect seems not to be evident for a dvanced OA produced ACL transection which accompanies macroscopic shap e changes. Relevance The present findings are relevant to the current research investigating the case of human osteoarthritis. We measured t he frictional coefficients of experimentally degenerated rabbit stifle s. The frictional coefficients can be used as an index of joint degene ration. We also assessed the recovery of the lubricating ability by ad dition of hyaluronic acid, a drug used for human osteoarthritis. (C) 1 997 Elsevier Science Ltd.