Pigmented villo-nodular synovitis (PVS) and teno-synovial giant-cell tumors (TSGCT) are rare diseases of joints, tendon-sheaths and other synovial structures. Regarding PVS the knee joint is the most often involved joint and TSGCT are mostly located in the tendon-sheaths of fingers. Both diseases mostly occur in adults but are also observed in children. Symptoms of both diseases are non-specific. Optimal diagnosis includes an X-ray of the involved structure and a MRI. For PVS optimal therapy is a complete synovectomy, whereas, in TSGCT tumors resection of the tumor itself within marginal margins is sufficient. Because of the high rate of recurrence (up to 50 %) in cases suffering from PVS adjuvant therapeutical strategies such as postoperative radiation or radio-synoviorthesis are recommended. Although there are no significant analyses confirming the effect of an adjuvant therapy on the rate of recurrence scientifically at least there is a tendency that these strategies may reduce the rate of recurrence. Malignant dedifferentiation is rarely seen. The prognosis of the mostly benign disease depends on the extent of the disease, the involved structure, additional bony involvement and still existing degenerative changes. In TSGCT no severe sequelae are known. In contrast, PVS in the hip regularly is followed by a secondary osteoarthrosis, in other joints degenerative changes are depending on the still existing changes at the date of diagnosis. Data on the long-term prognosis are rare and only analysed retrospectively.