Pigmented Villonodular Synovitis (PVS) is a proliferative disease that often occurs in synovial joints, tendon sheaths, and bursae of unknown etiology. The lesions often present as villi or nodular fibrous connective tissue protrusions, or both. Hyperpigmented villous nodular synovitis is the end result of chronic synovitis and recurrent bleeding. PVS has an insidious onset, a long course, and progressive symptoms. The most common knee symptom is swelling and progressively more painful discomfort and stiffness in one joint. Patients may or may not have a history of trauma. When the lesion involves cartilage and bone, symptoms such as painful walking up and down stairs, semi-squatting pain, ringing sounds in the joint during extension and flexion, and interlocking may occur. These symptoms of bone and cartilage lesions are not characteristic, but instead often confuse the diagnosis. Examination may reveal swelling of the joint, especially in the suprapatellar capsule, and sometimes synovial masses or nodules may be felt. Aspiration of dark red or brown bloody synovial fluid by arthrocentesis may reveal the disease, but is not specific, and in some patients the fluid may be yellow-green. Laboratory analysis of synovial fluid is also not specific and is therefore not diagnostic. The main manifestations of PVS of the knee on X-ray are joint swelling without calcification and, in severe cases of joint bone destruction, round-like erosive defects, but the imaging changes themselves lack specificity and do not allow a definitive diagnosis. MRI has been used as the most sensitive method for the early diagnosis of PVS because of its characteristic features: whether the lesion is diffuse or limited, the MRI presentation corresponds to its corresponding pathological component. The T2-weighted image is even more depressed, and may be accompanied by signs such as joint effusion or joint space shrinkage. Complete removal of the diseased synovial tissue is the key to the treatment of PVS. The knee joint is used as an example. Pigmented villous nodular synovitis is classified as diffuse or limited. For limited lesions, local excision of the lesion via arthroscopy is satisfactory and has the advantages of less surgical trauma, fewer complications, and shorter recovery time, so it should be the treatment of choice. There are many ways to treat diffuse PVS lesions. Subtotal synovectomy, radiation therapy, surgery plus radiation therapy, arthrodesis, arthroplasty, etc. have been used. Total synovectomy is currently the more advocated procedure. However, neither open surgery nor arthroscopic total synovectomy can completely remove the synovium and cure the diffuse lesion. Monoradiotherapy is effective when the PVS lesion is in its early stages, but when it is advanced and contains large amounts of fibrin, it is less responsive to radiation therapy and has the potential to induce sarcoma in young people. Subtotal synovectomy supplemented with radiation therapy can reduce complications and recurrence rates. Arthroplasty can also be performed in advanced stages affecting joint motion and pain to achieve good results and function.