title: Posteromedial knee friction syndrome: an entity with medial knee pain and edema between the femoral condyle, sartorius and gracilis.
abstract: OBJECTIVE
  To describe MRI features of an entity consisting of medial knee pain and edema between the posteromedial femoral condyle (PMFC), sartorius and/or gracilis tendons and determine whether reduced tendon-bone distances may account for these findings.
  
  
  METHODS
  We retrospectively identified MRI cases of edema between the PMFC, sartorius and/or gracilis tendons (25 subjects, 26 knees). Two musculoskeletal radiologists independently graded edema and measured the sartorius- and gracilis-PMFC distances and knee flexion angle. Age- and gender-matched subjects with normal knee MRIs (27 subjects, 27 knees) served as controls for measurements. Statistical analyses compared abnormal to control subjects.
  
  
  RESULTS
  Sartorius-PMFC and gracilis-PMFC spaces were narrower in abnormal compared to control subjects (1.6 ± 1.0 vs. 2.1 ± 1.2 mm, P = 0.04; 2.3 ± 2.0 vs. 4.6 ± 3.0 mm, P = 0.002, respectively). The knee flexion angle was similar between groups (P > 0.05). In subjects with clinical information, medial knee pain was the main complaint in 58 % (15/26) of abnormal subjects, with 42 % (11/26) having clinical suspicion of medial meniscal tear. Edema between the PMFC, sartorius and/or gracilis was mild in 54 % (14/26), moderate in 35 % (9/26) and severe in 12 % (3/26), and it was most frequent deep to both the sartorius and gracilis (50 %, 13/26).
  
  
  CONCLUSIONS
  Edema between the PMFC, sartorius and/or gracilis tendons identified on knee MRI may be associated with medial knee pain and may represent a friction syndrome.
authors.affiliation: Division of Musculoskeletal Imaging and Intervention, Department of Radiology, Massachusetts General Hospital and Harvard Medical School, 55 Fruit Street-YAW 6048, Boston, MA, 02114, USA.
authors.forename: F Joseph
authors.initials: FJ
authors.lastname: Simeone
authors.forename: Ambrose J
authors.initials: AJ
authors.lastname: Huang
authors.forename: Connie Y
authors.initials: CY
authors.lastname: Chang
authors.forename: Maximilian
authors.initials: M
authors.lastname: Smith
authors.forename: Thomas J
authors.initials: TJ
authors.lastname: Gill
authors.forename: Miriam A
authors.initials: MA
authors.lastname: Bredella
authors.forename: Martin
authors.initials: M
authors.lastname: Torriani
mesh_terms: D000328:Adult; D002357:Cartilage Diseases / Q000150:complications / Q000473:pathology*; D004487:Edema / Q000209:etiology / Q000473:pathology*; D005260:Female; D005269:Femur / Q000473:pathology; D017276:Friction; D006801:Humans; D007718:Knee Injuries / Q000150:complications / Q000473:pathology*; D007719:Knee Joint / Q000473:pathology*; D008279:Magnetic Resonance Imaging; D008297:Male; D015588:Observer Variation; D010146:Pain / Q000209:etiology / Q000473:pathology*; D012189:Retrospective Studies; D013577:Syndrome