title: Patellar tendinitis: MR imaging features, with suggested pathogenesis and proposed classification.
abstract: OBJECTIVE
  To characterize the magnetic resonance (MR) imaging features of patellar tendinitis.
  
  
  METHODS
  Fifteen patients with a clinical diagnosis of patellar tendinitis underwent gadolinium-enhanced MR imaging of the knee.
  
  
  RESULTS
  Grades of patellar abnormality, based on findings in the enthesial region at MR imaging, correlated with signs of increasing fibrovascular repair: grade 1 (n = 4), enhancing area adjacent to patellar apex, with marginal zone of intermediate signal intensity, and a patellar apical chondral-bone avulsion; grade 2 (n = 5), same signs as grade 1 damage but without avulsion; grade 3 (n = 6), homogeneous, nonenhancing area of intermediate signal intensity adjacent to the patellar apex seen on all images. Changes were most obvious posteriorly and involved the central and medial thirds of the tendon. Chronic injury to the medial retinaculum was a common associated finding.
  
  
  CONCLUSIONS
  Patellar tendinitis demonstrates a consistent spectrum of changes at MR imaging that can aid understanding of the origin and treatment of damage.
mesh_terms: D000293:Adolescent; D000328:Adult; D001265:Athletic Injuries / Q000145:classification / Q000209:etiology / Q000473:pathology*; D002358:Cartilage, Articular / Q000293:injuries / Q000473:pathology; D002908:Chronic Disease; D003287:Contrast Media; D005260:Female; D050723:Fractures, Bone / Q000145:classification / Q000209:etiology / Q000473:pathology; D050724:Fractures, Cartilage; D005682:Gadolinium; D019786:Gadolinium DTPA; D006801:Humans; D004204:Joint Dislocations / Q000145:classification / Q000209:etiology / Q000473:pathology; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D009942:Organometallic Compounds; D010329:Patella / Q000293:injuries / Q000473:pathology; D017847:Patellar Ligament / Q000293:injuries / Q000473:pathology; D004369:Pentetic Acid / Q000031:analogs & derivatives; D012421:Rupture; D052256:Tendinopathy / Q000145:classification / Q000209:etiology / Q000473:pathology*
chemical_list: D003287:Contrast Media; D009942:Organometallic Compounds; D004369:Pentetic Acid; D005682:Gadolinium; D019786:Gadolinium DTPA