Procaine and saline have similar effects on articular cartilage and synovium in rat knee.

Background: Intra-articular local anaesthetics are widely used for providing postoperative analgesia and decreasing the need for opioids. Procaine has proven positive effects in carpal tunnel syndrome and chondromalacia patella. However, the effect of procaine on articular cartilage has not yet been studied. The aim of this study was to evaluate the effects of intra-articular procaine injection on the articular cartilage and the synovium.

Methods: Twenty adult Sprague-Dawley rats were enrolled in the study. After providing anaesthesia and aseptic conditions, 0.25 ml of 10% procaine was injected to the right knee joint, and 0.25 ml of normal saline (as control group) was injected to the left knee joint. Knee joint samples were obtained from four rats in each group after appropriate euthanasia on days 1, 2, 7, 14 and 21. The histological sections of the articular and periarticular regions and the synovium were evaluated by two histologists, and inflammatory changes were graded according to a five-point scale in a blinded manner. The apoptosis of chondrocytes was determined by the caspase-3 indirect immunoperoxidase method.

Results: There were no significant differences in inflammation between procaine and saline groups at any of the time intervals. Slight inflammatory infiltration due to injection was seen in both groups on the 1st day. Haemorrhage was observed in both groups at days 1 and 2, and the difference between groups was not found to be significant. No significant difference was detected in the percentage of apoptotic chondrocytes between groups at any of the time intervals.

Conclusions: Injection of procaine seems safe to use intra-articularly based on this in vivo study on rat knee cartilage. However, further studies investigating both the analgesic and histopathological effects of procaine on damaged articular cartilage and synovium models are needed.