title: Longitudinal assessment of cyst-like lesions of the knee and their relation to radiographic osteoarthritis and MRI-detected effusion and synovitis in patients with knee pain.
abstract: BACKGROUND
  The purpose of the present study was to determine the prevalence of cystic lesions and cyst-like bursitides in subjects with frequent knee pain and to assess their relation to radiographic osteoarthritis (OA) severity; to describe bilaterality and size fluctuation of the lesions over 6 months; and to assess relations between the prevalence of synovium-lined lesions communicating with the joint capsule and severity of magnetic resonance imaging (MRI)-detected effusion and synovitis.
  
  
  METHODS
  One hundred and sixty-three subjects (total 319 knees) aged 35 to 65 with chronic, frequent knee pain were included. Imaging with 3 Tesla MRI was performed at baseline and 6-month follow-up with the same protocols as those used in the Osteoarthritis Initiative. Severity of radiographic OA was assessed using the Kellgren-Lawrence grade (0 to 4). Severity of effusion and synovitis was graded 0 to 3 based on the Whole Organ Magnetic Resonance Imaging Score system. The associations of cysts and cyst-like bursitides and severity of radiographic OA, MRI-detected effusion and synovitis were analyzed using logistic regression controlling for clustering by person. The Wilcoxon signed-rank test was used to determine whether there was a significant change in the size of lesions between baseline and follow-up.
  
  
  RESULTS
  At least one lesion (any type) was present in 222 (70%) knees. The most prevalent lesions were popliteal cysts (40%, 128/319), followed by subgastrocnemius bursitis (15%, 49/319) and proximal tibiofibular joint cysts (8%, 26/319). Bilateral lesions were seen in 49% of the subjects. Only popliteal cysts and subgastrocnemius bursitis showed a significant change in size (P < 0.001). No trend was observed between prevalence of any of the cyst-like lesions analyzed and the increasing radiographic OA severity. Increasing prevalence of subgastrocnemius bursitis was associated with increasing severity of effusion (P = 0.0072) and synovitis (P = 0.0033).
  
  
  CONCLUSIONS
  None of the cyst-like lesions analyzed seems to be a marker of radiographic OA severity in knees with chronic frequent pain. Subgastrocnemius bursitis may be used as a marker of effusion/synovitis severity. Bilateral cyst-like lesions are relatively commonly observed in people with chronic knee pain.
authors.affiliation: Quantitative Imaging Center, Department of Radiology, Boston University School of Medicine, FGH Building 3rd Floor, 820 Harrison Avenue, Boston, MA 02118, USA. Daichi.Hayashi@bmc.org
authors.forename: Daichi
authors.initials: D
authors.lastname: Hayashi
authors.forename: Frank W
authors.initials: FW
authors.lastname: Roemer
authors.forename: Zineb
authors.initials: Z
authors.lastname: Dhina
authors.forename: C Kent
authors.initials: CK
authors.lastname: Kwoh
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Hannon
authors.forename: Carolyn
authors.initials: C
authors.lastname: Moore
authors.forename: Ali
authors.initials: A
authors.lastname: Guermazi
mesh_terms: D000328:Adult; D000368:Aged; D002062:Bursitis / Q000453:epidemiology* / Q000473:pathology; D003560:Cysts / Q000453:epidemiology / Q000473:pathology; D005122:Exudates and Transudates; D006801:Humans; D007719:Knee Joint / Q000473:pathology*; D008137:Longitudinal Studies; D008279:Magnetic Resonance Imaging; D008875:Middle Aged; D020370:Osteoarthritis, Knee / Q000473:pathology*; D010146:Pain / Q000473:pathology*; D011151:Popliteal Cyst / Q000453:epidemiology* / Q000473:pathology; D015995:Prevalence; D013585:Synovitis / Q000473:pathology*