title: Arthroscopic patterns of the poster-medial aspect of the knee joint: classification of the gastrocnemius-semimembranosus gateway and its relationship with Baker's cyst.
abstract: BACKGROUND
  The gastrocnemius-semimembranosus bursa may communicate with the knee joint. The arthroscopic anatomy of the posteromedial aspect varies depending on the angle of the oblique popliteal ligament, the level at which it crosses the medial gastrocnemius tendon, and its relationship with the capsular joint and synovia. The aim of this paper is to identify possible patterns, and to evaluate their characteristics and their relationship with Baker's cyst.
  
  
  METHODS
  data archived from 185 consecutive arthroscopies were evaluated; an anatomic description and classification was carried out; the percentages of association with BC and the associated pathologies were reported.
  
  
  RESULTS
  The different anatomies were classified into six groups based on the relationship above the medial gastrocnemius tendon, the capsular joint and synovia. The prevalence of Baker's cyst was 28.3%. The main associated intra-articular pathological condition was the contemporary presence of a meniscal tear and chondropathy.
  
  
  CONCLUSIONS
  Exploration of the posterior aspect of the knee must be performed routinely. Knowing the possible anatomy patterns of the posteromedial arthroscopic aspect of the knee joint could help to identify the cyst and its gateway, thus facilitating its treatment.
  III.
authors.affiliation: Department of Orthopaedic and Traumatology School, University of L'Aquila, Italy.
authors.forename: Vittorio
authors.initials: V
authors.lastname: Calvisi
authors.affiliation: Regina Elena National Cancer Institute, Oncological Orthopedic Department, Rome, Italy.
authors.forename: Carmine
authors.initials: C
authors.lastname: Zoccali
keywords: Baker’s cyst; arthroscopic portal; arthroscopy; knee arthroscopic anatomy