Hyaluronan injection affects neither osteoarthritis progression nor loading of the OA knee in dogs

We previously reported that intraarticular injections of hyaluronan (HA), administered prophylactically to dogs in whom knee osteoarthritis had been induced by transection of the anterior cruicate ligament, did not significantly modify the intraarticular pathology but decreased the proteogylcan concentration of the articular cartilage by as much as 30%. Because the cartilage proteoglycan concentration is directly related to the stiffness of the tissue, these results raised the possibility that intraarticular HA therapy could exacerbate OA. In the present study, using a different HA formulation, with a longer interval between intraarticular HA injection and examination of joint tissues, we found that neither prophylactic nor therapeutic administration of HA had an effect on the severity of OA pathology, the magnitude of vertical ground reaction forces generated by the unstable hind limb (a surrogate for joint pain), or the cartilage proteoglycan concentration. The data suggest that the suppression of proteoglycan synthesis induced by HA is temporary and fully reversible and that HA injections do not result in overloading of the OA extremity. A significant correlation was noted between the severity of chondropathy and the magnitude of the vertical ground reaction forces generated by the unstable limb.