Proximal dissection of a popliteal giant synovial cyst: a case report.

Giant synovial cysts in patients with rheumatoid arthritis are well-recognized soft-tissue masses adjacent to the knee. Cases involving the elbow, hip, and other synovial joints have been reported as well. Regardless of location, these expanding, space-occupying lesions usually present with nonspecific symptoms of swelling and pain. Less commonly, the original presentation may be related to the secondary effects of the cyst on nearby anatomic structures. We present a case of a giant synovial cyst originating posteriorly in the knee, which, rather than dissecting distally into the calf, dissected proximally into the posterior soft tissue of the thigh in a patient with long-standing rheumatoid arthritis.