Effect of intraarticular hyaluronan injection on synovial fluid hyaluronanin the early stage of canine post-traumatic osteoarthritis

Objective. To determine how the quantity and molecular weight of synovial f luid hyaluronan (HA) within the synovial fluid (SF) of osteoarthritis (OA) joints is affected by intraarticular injection of HA. Methods. Dogs in which OA was induced by transection of the anterior crucia te ligament received 5 weekly injections of HA (1.5 x 10(6) Da) in saline ( 10 mg/0.67 ml) or an equal volume of saline into the operated knee, beginni ng the day after surgery. Immediately before each injection, SF was aspirat ed and the volume of SF and the concentration of HA was measured (uronic ac id), and the molecular weight of the HA in each sample was estimated by ele ctrophoresis in agarose. Results. The volume of SF in the unstable knee increased after surgery, and the molecular weight decreased from similar to2.5 x 10(6) Da to similar to 2 x 10(6) Da. Injection of HA did not affect the volume of SF or average mo lecular weight of HA in samples obtained immediately before each injection or at the end of the experiment, 12 weeks after surgery. The SF HA concentr ation fell from a baseline value of 2.3 +/- 0.1 mg/ml to 1.1 +/- 0.2 mg/ml the day after surgery and remained low throughout the course of injections. The HA concentration 12 weeks after surgery in the HA injected knees was s imilar to 40% lower than the preoperative value, although it increased slig htly relative to saline injected knees (1.4 +/- 0.3 vs 1.1 +/- 0.01 mg/ml, respectively; p = 0.04). Conclusion. Intraarticular injection of HA did not alter the volume of SF o r molecular weight of HA in SF of OA canine knees, nor did it restore the H A concentration to that of normal canine SF.