Synovial hyperplasia is the massive growth of synovial membrane due to external stimuli, such as osteoarthritis and trauma. Synovial membrane can secrete synovial fluid to nourish articular cartilage and meniscus and lubricate joints, and it can also reabsorb synovial fluid to form joint fluid circulation. If synovial hyperplasia occurs, the synovial membrane will secrete a large amount of inflammatory synovial fluid and its function of reabsorbing synovial fluid will be inhibited, resulting in excessive intra-articular fluid and clinical manifestations such as joint swelling and joint effusion. If intra-articular hemorrhage is caused by trauma, the synovial membrane will be stimulated and lead to synovial hyperplasia, which may result in pigmented villous nodular synovitis. The disease has a low malignant tendency, and treatment requires arthroscopic total synovectomy and postoperative intra-articular radiotherapy to prevent recurrence. In contrast, synovitis due to osteoarthritis requires joint rest and braking, physical therapy, and oral anti-inflammatory and pain medications that can relieve synovial hyperplasia symptoms.