Pigmented villous nodular synovitis is relatively rare, and there are two types: villous and nodular. Patients are mostly young and middle-aged men. They are mostly between the ages of 20 and 40. The disease is most common in the knee and ankle joints, followed by the hip, intertarsal, wrist, elbow and other joints, and occasionally in the bursa and tendon sheath.
1.Pathological manifestations
The disease may be a synovial disease between inflammation and benign tumor. The villous type is more similar to inflammatory disease. Animal studies have demonstrated that repeated injections of blood into the joint cavity can produce the same pathologic changes as the villous type. Similar changes may be seen in athletes with repeated knee bleeding. The nodular type is composed of a large number of synovial cells and is prone to recurrence if not completely excised, thus resembling a benign tumor.
In the villous type, the synovial membrane is dark red or brownish yellow and often thickens significantly, up to 1 cm or more. The synovial surface is uneven and often has folds and villi. Some of the villi are long and thin, up to 1 to 2 cm long, and float in the water like whiskers; others are shorter and fuse with each other to form nodules. The diameter of the nodules ranged from 1cm to 4-5cm. Smaller nodules were reddish brown, while larger nodules were yellowish white with rusty spots. The nodules are slightly stiff and tough, and swirling fibrous tissue is seen in section, with occasional mucus degeneration and fissures. In some cases, there are both villous and nodular lesions.
The distribution of lesions can be classified as diffuse or limited. Diffuse lesions are more common, and a few are limited. In diffuse lesions, the villi and villi nodules are usually of the nodular type, and in limited cases, they are usually of the nodular type.
Microscopically, the surface of the villi is composed of several layers of synovial cells with a little fibrous tissue, dilated capillaries and a few inflammatory cells in the center. Iron-containing haematoxylin granules are visible inside and outside the cells. The nodules consisted of dense synovial cells with little cytoplasm, indistinct cytosol, and dark nuclear staining. Fissures and papillae were seen in the dense cells. Multinucleated giant cells and foam cells were occasionally seen between the synovial cells.
2.Clinical manifestations
The disease has no obvious systemic symptoms, the patient’s body temperature is not high, the blood sedimentation is not fast, and the blood picture is not changed. The local symptoms are also mild in the early stage, so the patients are diagnosed late and have a long disease duration, and most of them have a history of trauma.
The main symptom of the disease is joint swelling, pain is relatively mild, local skin temperature is sometimes slightly high, and joint function is not significantly limited. In diffusely swollen joints, the thickened synovial membrane is spongy to the touch, and fluctuating sensations can be palpated in cases of fluid accumulation. Sometimes nodules of varying size and slightly mobile can be palpated.
The suprapatellar bursa and patella are obviously swollen when the knee is involved, and the patella test is positive if there is a lot of fluid. The hyperplastic synovial tissue may sometimes penetrate the posterior joint capsule and enter the N fossa and spread down the posterior calf muscle space, producing a deep diffuse swelling. Swelling is most pronounced around the inner and outer ankles in ankle involvement. In the case of hip involvement, the swelling is mostly located anterior to the hip joint.
Whether diffuse or limited, there is mild muscle atrophy in the affected limb. Joint puncture can extract bloody or coffee-colored fluid, which is a special kind of joint fluid and has diagnostic value.
3.Diagnosis
(1) Clinical manifestations
(2) Arthrocentesis
(3) Nuclear magnetic resonance examination
(4) Arthroscopy
(5) Pathological diagnosis
4.Treatment
(1) Arthroscopic excision of diseased synovial membrane
(2) Radiation therapy is better for the choroidal type, but not effective for the nodular type