Hip effusion is a manifestation of inflammation of the bone, cartilage, synovium and surrounding soft tissues of the hip. The effusion is mainly produced by the secretion of synovial fluid, which is stimulated by various etiologies (such as osteophytes, arthritis, joint tuberculosis, rheumatism, etc. and traumatic trauma, bone injury, intra-articular injury, surrounding soft tissue injury, surgery, etc.) or directly stimulated by synovial injury to produce an inflammatory response, and the synovial membrane responds to the stimulation of inflammation by secreting exudate that Synovitis is a sterile inflammation caused by poor microcirculation, and the main symptom is the production of fluid. The synovial membrane is a layer of membranous tissue surrounding the joint, which is connected to the joint cavity and secretes lubricating fluid to lubricate the joint. It is not only a layer of tissue that protects the joints, but also produces joint fluid, providing “lubricating fluid” for joint movement. The production and absorption of joint fluid is a dynamic balance. When the reabsorption of joint fluid is impaired, joint effusion occurs because the dynamic balance of joint fluid production and absorption is disrupted and the production of joint fluid is greater than reabsorption. Therefore, as long as there is exudate accumulation in the joint, it proves the existence of synovial inflammation, whose main manifestations are joint congestion and swelling, pain, increased exudate, joint effusion, difficulty in moving and squatting, and functional limitation. Therefore, the main treatment of synovitis is to regulate the microcirculatory system, as long as the microcirculation is smooth, the fluid will disappear, and the inflammation will also be lifted. There are many causes of hip effusion, the most important ones are osteoarthritis, compulsory spondylitis, rheumatoid arthritis and hip tuberculosis. Osteoarthritis of the hip joint mainly manifests as soreness and swelling in the groin after activity or weight-bearing, and radiates along the front and back of the thigh to the knee joint, as well as soreness and swelling around the hip and at the greater trochanter of the femur, and walking with a limp. The most common cause of hip lesions is ankylosing spondylitis. In addition, if a single hip joint lesion produces effusion, we should pay more attention to hip joint tuberculosis, which is the most common site of bone and joint tuberculosis after the thoracic spine. From time to time, we encounter single hip lesions that make it difficult to distinguish between tuberculosis and immunity. At this time, there are 2 aspects to refer to: first, MRI examination of the hip joint, if the surrounding soft tissues are obviously swollen, it supports tuberculosis; second, close follow-up, if there is obvious progression of radiological damage within 1 to 3 months, it is tuberculosis.