Introduction

Synovial chondromatosis is a rare disorder characterized by formation of cartilaginous bodies within the synovia of different joints, tendon sheaths, and bursae secondary to synovial metaplastic process. It is likely a process caused by hyperplastic metaplasia of the synovial tissue. 
The exact synovial stimulus ending up with synovial metaplasia is still unknown. Embryonic remnants have been postulated to define the etiology. Although infection has been postulated as a causative factor, cultures remain negative. Trauma has been implicated as a precipitating factor in half of the patients in one study.
Synovial chondromatosis has been classified into three stages. During the first stage, the synovial lining undergoes cartilaginous metaplasia. At the second stage, the nodules begin to detach from the synovium and appear as loose bodies. During this stage, the patients become symptomatic. At the third stage the synovial lining is destroyed without any evidence of chondral metaplasia. Ossification of the nodules is possible during the third stage of the disease. 
Synovial chondromatosis is most common in 20-50 year old male patients and frequently involves large joints including the knee, hip, elbow and ankle, with the knee accounting for more than 50% of reported cases. Disease is usually intraarticular and characteristically monoarticular.

History and Physical Examination

History
Symptoms include pain at rest or on movement, crepitation, joint stiffness as well as decreased movement, and sometimes locking or catching sensation.

Physical Examination 
The physical findings vary with the joint involved and with the degree of involvement. The range of motion of the affected joint can be decreased. There can be a localized or diffuse swelling of the joint with palpable fixed or loose bodies.
Differential diagnostically disorders that may give rise to loose bodies such as degenerative joint disease, arthritis, and osteochondral lesions. 

Diagnostic Imaging

The radiographic features change according to stage of the disease. Calcification usually appears late and may not be present at all. In longstanding conditions, osteoarthritic changes can be seen. The most frequent and characteristic rontgenographic finding is multiple, small, radiopaque masses of varying size, which can only be visible in some part of the joint area. The radiographs may only reveal increased soft tissue density around the affected joint.

For pre-operative planning and when bony lesions are suspected, we usually make a CT-scan. However, for diagnostic purposes MRI is more sensitive in chondromatosis because the loose bodies are predominantly cartilaginous. 

Post-operative rehabilitation

The patient can be discharged the same day of surgery and weightbearing is allowed as tolerated. The patient is instructed to perform active dorsiflexion of the ankle to the neutral position (knee slightly bent). This exercise should be performed 2 or 3 days times per hour for the first days after surgery. The patient is instructed to elevate the foot when not walking to prevent edema. The dressing is removed 3 days post-operative. Normal walking without crutches at 4 - 5 days post surgery. Patients with limited range of motion are directed to a physiotherapist. Running can be started when range of motion is normal and in absence of swelling. This can on avarage be expected at 3 weeks post surgery. Sport resumption can on average be expected at 6 weeks post surgery. 

Recommended literature

Van Dijk CN, Fievez AWFM, Heijboer MP, et al. Arthroscopy of the ankle. Acta Orthop Scand 1993;64(suppl. 253):9.

Van Dijk CN, Scholte D. Arthoscopy of the Ankle Joint. Arthroscopy: The journal of Arthroscopic and Related Surgery, 1997;13(1):90-96.

Van Dijk, Verhagen RAW, Tol JL. Arthroscopy for problems after ankle fracture. J Bone Joint Surg (Br) 1997;79B(2):280-284.