A two stage, controlled animal trial was designed to observe the effects on normal and manually damaged articular cartilage of the rat knee joint of colchicine (COL) and diclofenac sodium (DIC) added into washout solutions. In the first stage, 21 rats were randomized into three groups, and right knees of all groups were washed-out by either COL, DIC or physiologic saline (PS) solutions. The left side was kept as a paired control. After 18 months, all knees were evaluated macroscopically and microscopically for cartilage changes. In the second stage, 25 rats were randomized into four groups, and a 2x2 mm defect was created surgically on the medial condyle. The joints were washed out by either COL, DIC or PS solutions. At the end of the six months, macroscopic, microscopic and transmission electron microscopy (TEM) evaluations were performed to observe the changes to the defective area. The results showed that washout procedures with certain arthroscopic fluid modifications revealed macroscopically less fibrillation and surface changes for the COL and DIC groups in the first stage. Colchicine and diclofenac sodium solutions conducted a better effect on the thickness of the cartilage and gave better results according to Mankin's criteria for degeneration. In the second stage, COL and DIC groups showed better effects on the cartilage regeneration. The pharmacological agents added into the arthroscopic washout fluid may have an effect on the ultrastructure and biologic properties of the joint cartilage, and may improve the results of arthroscopic treatment in chondral pathologies, especially in secondary arthritis.