Arthroscopic anatomic study of posteromedial joint capsule in knee joint associated with popliteal cyst

The purpose of this study was to examine the arthroscopic anatomy of posteromedial capsule and magnetic resonance imaging (MRI) findings in internal derangement of the knee joint and to analyze the relationship between popliteal cysts and the posteromedial capsule.

From 2011 to 2012, a prospective study included 194 knees of consecutive arthroscopic surgeries for assorted knee problems. The anatomy of the posteromedial joint capsule was evaluated arthroscopically and divided into three types by the presence of capsular fold and opening: no capsular fold and no opening (type I), capsular fold without opening (type II), capsular fold with opening (type III). The presence and size of popliteal cyst were documented by MRI.

Type I was observed in 160 knees (82.5 %), type II in 10 (5.1 %) and type III in 24 (12.4 %). Popliteal cysts were found in 25 knees (12.9 %) by MRI. Of these cases, symptomatic popliteal cysts were identified in 12 knees (6.9 %). On 160 knees demonstrated to be type I, only 3 knees (1.9 %) had popliteal cysts in MRI, 6 knees (60 %) in 10 knees of type II and 16 knees (66.7 %) in 24 knees of type III. Therefore, there was a statistically significant relationship between the type of anatomy in the posteromedial capsule and the popliteal cyst (p < 0.001).

An association between popliteal cyst and arthroscopic anatomy of posteromedial capsule was demonstrated. Comprehensive understanding and knowledge of the arthroscopic anatomy of posteromedial capsule would contribute to the arthroscopic approach in understanding the pathogenesis of popliteal cyst.

Development of diagnostic criteria on basis of consecutive patients.

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