title: Natural history of popliteal cysts in the pediatric population.
abstract: BACKGROUND
  Cystic mass lesions in the popliteal area, called popliteal cysts or Baker's cysts, are usually minimally symptomatic and not related to intra-articular morbidity in the pediatric population. Although multiple studies have described cases of spontaneous resolution over a period of several months to a few years, others still consider surgical treatment necessary. Furthermore, no previous studies have used magnetic resonance imaging (MRI) to confirm the disappearance of popliteal cysts. In this retrospective study, we reviewed records of patients with popliteal cysts to investigate the natural history of this disease.
  
  
  METHODS
  The medical records of patients with popliteal cysts followed for at least 12 months were retrospectively reviewed. The patient set comprised of 17 knees in 15 males and 3 knees in 2 females. Mean age was 5.6±2.0 years (range, 1.8 to 11.4 y) at their initial visit to the clinic, and mean follow-up period was 53.1±31.6 months (range, 12.6 to 147.8 mo). MRI findings were reviewed for the 16 knees in 13 patients who had undergone MRI. Symptoms and clinical course were extracted from the medical records of all the study subjects and analyzed.
  
  
  RESULTS
  Although 6 knees (30%) had histories of pain in the popliteal area, no patient complained of pain at their initial visit. Seventeen cysts (85%) naturally decreased in size or disappeared on clinical examination and/or ultrasound. Cysts confined to either the gastrocnemio-semimembranosus bursa or the subgastrocnemius bursa according to the MRI findings were classified as type I, and cysts which occupied both bursae were classified as type II. Eight knees received MRI examination more than once, and complete disappearance was confirmed in 5 of these knees. All type II cysts converted to type I, and all cysts which completely disappeared were type I before disappearance.
  
  
  CONCLUSIONS
  The MRI findings in our study population confirmed that popliteal cysts in pediatric populations can be expected to completely resolve in due course without treatment.
  
  
  METHODS
  Therapeutic study Level IV (Case series).
authors.affiliation: Department of Orthopaedic Surgery, Chiba Children's Hospital, Chiba, Japan. ryu-a@nona.dti.ne.jp
authors.forename: Ryuichiro
authors.initials: R
authors.lastname: Akagi
authors.forename: Takashi
authors.initials: T
authors.lastname: Saisu
authors.forename: Yuko
authors.initials: Y
authors.lastname: Segawa
authors.forename: Takahisa
authors.initials: T
authors.lastname: Sasho
authors.forename: Hideshige
authors.initials: H
authors.lastname: Moriya
authors.forename: Kazuhisa
authors.initials: K
authors.lastname: Takahashi
authors.forename: Makoto
authors.initials: M
authors.lastname: Kamegaya
mesh_terms: D002648:Child; D002675:Child, Preschool; D018450:Disease Progression; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D011151:Popliteal Cyst / Q000175:diagnosis*; D012189:Retrospective Studies