Ankle joint urate arthritis in rats provides a useful tool for the evaluation of analgesic and anti-arthritic agents.

Arthritis was induced in ether anesthetised rats by injecting 1.25 mg of sodium urate crystals into the ankle joint. Twenty-four hr after the injection the ankle is swollen and the animal does not place full weight on the affected foot. The ankle is more sensitive than normal to movement and pressure. Responses to stimulation of the foot and toes on the arthritic limb are reduced due to a reluctance to move the affected limb. These measures, which reflect ongoing pain, hyperalgesia or tenderness and guarding, are attenuated in animals treated with dexamethasone, phenylbutazone, and morphine, as well as in animals whose nerves to the ankle had been pretreated with capsaicin. Guanethidine and colchicine failed to influence the behavioural responses to the urate injection. Ankle joint urate arthritis has advantages over other models of arthritis for therapeutic testing in that in a short time it affects a single joint in rats, and it produces responses which can be assessed by simple, sensitive measures.