The pathology and evaluation of surgical treatment in a ruptured giant popliteal/crural cyst associated with rheumatoid arthritis

Abstract

Popliteal cysts are often observed in patients with rheumatoid arthritis (RA), and giant cysts that extend from the popliteal to the crural region (popliteal/crural cysts) are occasionally encountered. We studied the background of popliteal/crural cysts and therapeutic results, and evaluated its etiologic factors and the effectiveness of surgical treatment. Nine knees of eight patients with popliteal/crural cyst secondary to RA, which was treated surgically because it resisted conservative treatment, and was followed up for 1 year or longer after surgery, were evaluated. The patients were five men and three women, with a mean age at surgery of 59.1 years and a mean duration of RA disease of 4.5 years. Only one male patient suffered pain in the bilateral joints. The mean level of erythrocyte sedimentation rate was 61.3 mm/h (range 3.9–100.2), the mean level of C-reactive protein was 3.6 (0.1–8.2) mg/dl, and the mean Lansbury index was 36.4 (12–61) at surgery. The cyst disappeared completely after surgery, and the postoperative course was uneventful in eight knees, but recurrence was observed in just one knee of the bilateral case. However, in this patient the cyst that recurred was not as large as the one before surgery, and it was eventually brought under control by subsequent outpatient medical management. Inflammatory reactions were suppressed, if temporarily, in all patients. The patients evaluated in this study showed the following characteristics: the male–female ratio of the patients was biased to males compared with that of RA patients in general; although knee joint damage was radiographically mild, marked symptoms of arthritis were observed in not only the knees but also other joints in all patients; and the disease could not be controlled effectively by medication. However, after surgical resection of the cysts, general as well as local signs of inflammation were mitigated, and surgery was considered to be very effective for the treatment of ruptured giant popliteal/crural cyst associated with RA.