The synovial membrane is a very delicate structure. As a result of previous knee injuries or various rheumatic diseases, i.e. rheumatoid arthritis, juvenile idiopathic arthritis, gout, lupus erythematosus and systemic sclerosis, or in tumors and tuberculosis, it may overgrow, thus increasing its secretory activity. This leads to an overproduction of synovial fluid with an abnormal chemical composition, so its value as a substance facilitating the glide of the articular surfaces and nourishing the articular cartilage is significantly reduced, which leads to generalized synovitis.