title: MRI diagnosis of patellar clunk syndrome following total knee arthroplasty.
abstract: BACKGROUND
  Patellar Clunk Syndrome is a painful condition associated with a mechanical catching or clunking during active extension following total knee arthroplasty (TKA). The syndrome is caused by growth of interposing soft tissue usually at the superior pole of the patella. This interposed soft tissue cannot be visualized on plain radiographs.
  
  
  OBJECTIVE
  The aim was to ascertain if magnetic resonance imaging (MRI) would prove helpful in confirming the clinical diagnosis of patellar clunk by visualizing the interposed soft tissues adjacent to the patella and that the recognition of this tissue would be highly reproducible.
  
  
  METHODS
  MRI scans of 12 patients with clinical suspicion or related symptoms of a patellar clunk syndrome following primary TKA were retrospectively evaluated. Size of soft tissue masses proximal to the patella were determined in sagittal and axial MRI views. Largest diameters were recorded in two dimensions by two independent observers, and interobserver reliability was determined by intra-class correlation coefficients (ICC).
  
  
  RESULTS
  Nine patients (75%) showed obvious MRI findings consistent with a patellar clunk lesion with high interobserver reliability (ICC values >0.75). In eight patients, this lead to operative treatment with arthroscopic debridement.
  
  
  CONCLUSIONS
  MRI helps confirm the clinical diagnosis of patellar clunk. The data indicate that MRI is effective in defining the soft tissue lesion that is implicated in clinically evident patellar clunk syndrome after TKA.
authors.affiliation: Department of Orthopedics and Rheumatology, University Hospital Marburg, Baldingerstrasse, 35043 Marburg, Germany.
authors.forename: Thomas J
authors.initials: TJ
authors.lastname: Heyse
authors.forename: Le Roy
authors.initials: le R
authors.lastname: Chong
authors.forename: Jack
authors.initials: J
authors.lastname: Davis
authors.forename: Steven B
authors.initials: SB
authors.lastname: Haas
authors.forename: Mark P
authors.initials: MP
authors.lastname: Figgie
authors.forename: Hollis G
authors.initials: HG
authors.lastname: Potter
keywords: MRI; TKA; magnet resonance imaging; patellar clunk; total knee arthroplasty