Posterior interosseous nerve syndrome associated with rheumatoid synovial cysts of the elbow joint.

Three rheumatoid arthritis patients developed synovial cysts of the elbow joint and an acute compression neuropathy of the posterior interosseous nerve. All patients had weakness of the finger extensors; in one the extensor tendons were explored before the exact diagnosis was made. Intraarticular steroid injections were effective in one patient. In the other two patients surgical decompression of the radial nerve and elbow synovectomy with radial head resection were curative. Although relatively rare, the diagnosis of an antecubital cyst must be considered when complications such as a nerve compression syndrome are present.