Periarthritis promotes gait disturbance in zymosan-induced arthritis in rats

Objective and Design: We studied the contribution of periarthritis and syno vitis to gait disturbance in zymosan (Zy)-induced arthritis. Methods: Sixty Wistar rats were subjected to injection of Zy (1 mg) into th eir right knee joints. A first group of animals (GI) had Zy injected throug h the intact skin. A second group (GII) had Zy injected directly into the a rticular cavity after excision of the skin and subcutaneous tissue surround ing the joint. Gait disturbance was evaluated using the rat-knee joint inca pacitation test. Increase in vascular permeability and cell influx were ass essed in joint fluids and joint histology was performed. Results: Zy injection induced a dose-dependent gait disturbance which was m aximal at the third/fourth hour of arthritis, being significantly greater i n GI rats, whereas cell influx (neutrophils greater than or equal to 80%) w as maximal at the sixth hour. Cell influx and increase in vasopermeability did not differ between both groups. Histology revealed no significant diffe rence between GI and GII. A third group (GIII), subjected to immune-complex arthritis, that received anti-bovine serum albumin (BSA) antibodies intra- articularly and BSA i.v., did not present gait disturbance, despite the inc rease in cell counts. Conclusions: Vascular permeability increase and cell influx are phenomena i ndependent of gait disturbance. Neutrophils do not seem to contribute to de velopment of gait disturbance in Zy arthritis. Sensitization of specific pa in receptors in periarticular rather than in synovial tissue is responsible for gait disturbance in Zy-induced arthritis.