Primary Synovial Chondromatosis

A 62-year-old patient with increasing symptoms and progressive limitation of movement in the right elbow; clinical examination reveals diffuse joint swelling and marked limitation of flexion and extension
MRI findings: numerous loose bodies in the joint -> Elbow arthroscopy

Definition

Primary synovial chondromatosis (PSC) is a rare, benign growth of connective tissue beneath the synovial membrane. It leads to the formation of nodules of hyaline cartilage in joints, tendon sheaths, or bursae. These cartilaginous nodules can enlarge, detach from the synovial membrane, and act as loose bodies within the joint. The knee joint is most commonly affected.

Epidemiology

PSC occurs primarily in people in their third through fifth decades of life. Men are two to four times more likely to be affected than women.

Etiopathogenesis

The exact cause of PSC is unclear. While metaplasia was once thought to be the cause, it is now believed to be a benign neoplastic process.

Clinic

The knee joint is affected in 50–65% of cases, but other joints—such as the hip, elbow, shoulder, and ankle—may also be affected. Typical symptoms include:

On examination, diffuse joint swelling (40–60%), increased joint tenderness (20–40%), crepitus (20–33%), and joint locking (5–12%) are often observed. Palpable nodules are found in 3–20% of cases. Symptoms usually develop gradually and have often been present for years by the time of diagnosis.

Complications

PSC can lead to secondary osteoarthritis. Malignant transformation into a synovial chondrosarcoma is possible, with a prevalence of up to 5%. Chondrosarcoma can metastasize to the lungs; therefore, a biopsy is necessary in cases of rapid growth or clinical deterioration.

Diagnostics and Imaging

X-ray: Multiple intra-articular calcifications with typical ring- and arc-shaped mineralization.
CT: Hypodense, lobulated mass with hyperdense calcified fragments.
MRI: Variable signal intensity of the cartilage bodies, depending on the degree of mineralization.
Bone scintigraphy: Prominent radionuclide uptake.
Ultrasound: Heterogeneous mass with hyperechoic cartilage foci.

Therapy

PSC is treated with surgical synovectomy and removal of cartilage fragments. The recurrence rate is 3–23%, depending on the extent of the resection. In cases of repeated recurrences, radiation therapy may be considered.