For patients with a small amount of fluid in bilateral hip joints, this condition is mostly caused by bilateral hip synovitis. The small amount of fluid in the hip joint is related to strain injury and cold, which causes the synovial membrane inside the hip joint to be stimulated and then cause the synovial membrane to become edematous and hyperplastic, which will lead to an increase in the exuded fluid, causing a small amount of fluid in the hip joint bilaterally. Under normal circumstances, the synovial membrane secretes synovial fluid to lubricate the joint, but when the synovial membrane is stimulated, especially after the stimulation of the formation of aseptic inflammation, resulting in synovial edema, hyperplasia, the secretion of fluid increases, will break the balance of the fluid inside the joint, there is a fluid retention in the hip joint, the formation of a small amount of effusion.