This study investigated the possible local adverse effects of intra-articular administration of tenoxicam in the rat knee joint. A total of 50 rats were given 0.25 ml of a standard preparation of tenoxicam by injection into the right knee joint and 0.25 ml of 0.9% saline solution by injection into the left knee joint as a control. Groups of 10 rats were killed 24 h, 48 h, 7 days, 14 days and 21 days after tenoxicam administration. Two rats were sham operated; one was killed on the first day and the other on the second day after this procedure. All the joints were prepared and sectioned for histological examination. Tissue loss and oedema were observed in the specimens obtained 24 h and 48 h after treatment with tenoxicam.. No pathological changes were observed in the 7-day, 14-day and 21-day specimens, or in the control joints. Caution should be exercised when using intra-articular tenoxicam for postoperative analgesia.