O12 An ultrasonographic study for Baker's cyst in knee arthritidis

Introduction: There is paucity of studies regarding asymptomatic Baker’s cyst during the course of knee involvement in degenerative and inflammatory diseases. This prospective study was conducted to find out the prevalence and anatomical characteristic of this poplitial cyst. Objectives:To assess by ultrasonography the frequency of the popliteal cysts and its complications in patients with knee osteoarthritis (OA) and rheumatoid arthritis (RA) and seronegative spondyloarthritis (SSA). Methods: This prospective study included 112 patients with RA, 200 symptomatic patients with osteoarthritis of the knee and 150 patients of SSA who had had involvement of knee in form of pain or/and swollen joint. All patients had pain/discomfort in poplitial fossa or calf muscle. Results: In knee osteoarthitis the popliteal cysts were found in 122 patients (61.05%), 5 of them with bilateral cysts. the cysts usually had medium size (90% below 5 cm) or proliferated synovium (32% cysts). Dissection (8 cysts), rupture (6 cysts) and popliteal vein compression (1 cysts) were the complications encountered. Only 22 % of the cysts could be detected clinically. There were 8 knees with lipomatosis of the politeal fosa, which were clinically falsely interpreted as cysts. One patient had multiple cold abscesses extending from poplitial fossa to lower half of calf. The Baker’s cyst was detected in 62 RA patient (66.2%) but in 32 cases the cyst were bilateral (80 cysts in 158 knees). there is predominance of medium and large cysts over 5 cm (65% cysts), with proliferated synovium more than 0.4 cm (95% cysts) and in three patients with synovium calcifications. The complications encountered were dissection (10 cysts), rupture (2 cysts), deep vein thrombosis (2 cysts). On clinical examination, a popliteal cyst was detected only in 33 knees. (38.7%); all small cysts and the majority of the medium cysts were undetected. In 150 patients of SSA with knee involvement, 22 had unilateral and five had bilateral cyst. All were more than 5 cm in size (100%). The complications included dissection (2 cysts), rupture (2 cysts). In majority of patients, large cysts were drained successfully from posterior approach. Conclusion: There is a high frequency of Baker’s cysts in OA, RA and SSA patients. Ultrasonography is superior to the clinical examination in detection of small and medium cysts. Large cyst can be successfully drained from posterior approach.