Synovial Chondromatosis

Synovial chondromatosis is a benign condition that can result in severe disability and dysfunction of an involved synovial joint. Observation of involved cases indicates that this benign condition rarely undergoes malignant degeneration. The initial diagnosis is made through a thorough history and physical examination and radiological evaluation of an affected joint. These joints usually present as having a large effusion and sometimes appearing deformed due to swelling or synovial hypertrophy. They are painful at rest and are more painful with motion. The range of motion is usually decreased. X-ray evaluation reveals multiple loose radio-opaque chondroid bodies of varied sizes in a joint.  MRI arthrogram enables better evaluation of the process and the extent of involvement within the joint and surrounding tissue. Synovial chondromatosis is usually monoarticular although rare cases of multiple joint involvements occur. The process may occur in two forms: primary synovial chondromatosis (also referred to as Reichel syndrome) and secondary synovial chondromatosis). The primary and secondary forms have different presentations, and as such are treated differently. In rare cases, an extra-articular form of the condition can be identified. In these cases, the lesions are found to be in bursal tissue and/or in tenosynovial tissue in proximity to an involved joint.[1][2][3][4]

The etiology of the primary form has not been determined. Elevated levels of bone morphogenic protein in the loose body lesions and the affected synovial joints of patients with primary synovial chondromatosis have been documented. However, the etiological importance of this has not been determined. Similarly, elevated levels of interleukin-6 and vascular endothelial growth factor-A have been found in these joints, but the importance of these findings is not certain.  Secondary synovial chondromatosis is felt to occur ar a result of mechanical changes in a joint due to arthropathy. The formation of loose chondral bodies is thought to be part of the degenerative process in these joints.

Men are reported to be affected with synovial chondromatosis up to four times more commonly than women. The knee is most common joint affected. However, synovial chondromatosis can affect any synovial joint (the hip, the elbow, the shoulder, the temporal mandibular joint, and the ankle may also be affected). A rare occurrence is an extra-articular presentation of synovial-chondral lesions. This occurs in synovial lined bursal tissue or tenosynovium in which the typical chondral loose bodies form. These are referred to as tenosynovial chondromatosis or bursal chondromatosis. Synovial chondromatosis occurs most commonly in the fifth decade of life, it is rarely present before the age of 20, and it is very rare in children. Reference to both primary form (no evidence of concurrent joint pathology) and secondary form (occurring in the setting of joint degeneration) is made in the literature. The secondary form occurs more common and usually, in older individuals.

X-ray examination reveals irregularly shaped loose bodies within a synovial joint. This number varies anywhere from two or three loose bodies to several dozens. They present in varied sizes and several loose bodies may combine to form larger bodies. The number of intraarticular lesions is greater in the primary type than the secondary type. The gross and microscopic evaluation of the loose bodies reveals lobulated masses of hyaline cartilage surrounded by a layer of synovial tissue. The hyaline cartilage is hypercellular, and the cells are often atypical. These atypical changes are multinucleated cells, myxoid degeneration of matrix, crowding of cell nuclei, and large nuclei. In long-standing disease, the lobules can undergo peripheral ossification. High levels of bone morphogenic protein have been found in the loose cartilaginous bodies and synovial tissue. The loose bodies may create pathological mechanical wear on joint surfaces and result in various types of erosion of articular surfaces. The process is classified as a benign neoplastic rather than a metaplastic lesion.