Synovial oedema is a frequent complication in arthroscopic procedures performed with normal saline as the irrigating fluid. The authors have studied the effect of saline solution, Ringer lactate, 5% Dextran and 10% Dextran in normal saline on 12 specimens of human synovial membrane. They found that 10% Dextran in normal saline decreases the water content of the synovium without causing damage, and recommend this solution for procedures lasting longer than 30 minutes.