title: Knee effusions, popliteal cysts, and synovial thickening: association with knee pain in osteoarthritis.
abstract: OBJECTIVE
  To evaluate the association of effusions, popliteal cysts, and synovial thickening with knee symptoms in older persons with and without radiographic (XR) osteoarthritis (OA), using magnetic resonance imaging (MRI).
  
  
  METHODS
  Subjects with and without knee symptoms were recruited from Veterans Affairs and community sources. All had weight-bearing knee radiographs. Subjects were divided into 3 groups: Knee pain/XROA group had knee symptoms and radiographic OA; No knee pain/XROA group had no knee symptoms and radiographic OA; and No knee pain/no XROA group had no knee symptoms and a normal radiograph. A single knee was imaged using a 1.5 T MR scanner using T1 and T2 weighted and proton density SE imaging sequences. MRI were read for effusion, popliteal cysts, and synovial thickening.
  
  
  RESULTS
  The mean age of subjects was 67.0 years (66.6% male). We studied 381 subjects with Knee pain/XROA, 52 with No knee pain/XROA, and 25 with No knee pain/no XROA. The prevalence of moderate or larger effusions was: Knee pain/XROA 54.6%, No knee pain/XROA 15.6%, and No knee pain/no XROA 11.1%. Popliteal cysts were present in 33.0% of Knee pain/XROA subjects, 28.0% No knee pain/XROA, and 9.1% No knee pain/no XROA. After adjusting for the severity of radiographic OA, there was a difference between those with and without knee pain in prevalence of moderate or larger effusions (p < 0.001) and synovial thickening, independent of effusion (p < 0.001), but not in the prevalence of popliteal cysts. Further, among those in Knee pain/OA group, synovial thickening was associated with the severity of knee pain.
  
  
  CONCLUSIONS
  Effusions and popliteal cysts are common in middle aged and elderly people. After adjusting for the degree of radiographic OA, moderate or large effusions and synovial thickening were more frequent among those with knee pain than those without pain, suggesting these features are associated with the pain of knee OA. In those with knee symptoms, synovial thickening is uniquely associated with the severity of knee pain.
authors.affiliation: Boston University Arthritis Center, Boston, USA.
authors.forename: C L
authors.initials: CL
authors.lastname: Hill
authors.forename: D G
authors.initials: DG
authors.lastname: Gale
authors.forename: C E
authors.initials: CE
authors.lastname: Chaisson
authors.forename: K
authors.initials: K
authors.lastname: Skinner
authors.forename: L
authors.initials: L
authors.lastname: Kazis
authors.forename: M E
authors.initials: ME
authors.lastname: Gale
authors.forename: D T
authors.initials: DT
authors.lastname: Felson
mesh_terms: D000368:Aged; D005122:Exudates and Transudates; D005260:Female; D006801:Humans; D007719:Knee Joint / Q000473:pathology*; D008297:Male; D008875:Middle Aged; D020370:Osteoarthritis, Knee / Q000000981:diagnostic imaging / Q000453:epidemiology* / Q000473:pathology; D010146:Pain / Q000453:epidemiology* / Q000473:pathology; D011151:Popliteal Cyst / Q000000981:diagnostic imaging / Q000453:epidemiology* / Q000473:pathology; D015995:Prevalence; D011859:Radiography; D013583:Synovial Membrane / Q000473:pathology; D013585:Synovitis / Q000000981:diagnostic imaging / Q000453:epidemiology / Q000473:pathology