title: Denuded subchondral bone and knee pain in persons with knee osteoarthritis.
abstract: OBJECTIVE
  It is unclear how articular cartilage loss contributes to pain in patients with knee osteoarthritis (OA). Full-thickness cartilage defects expose the subchondral bone plate. The relationship between denuded bone and pain has not been examined. The aim of this study was to investigate whether the percent of denuded bone is associated with moderate-to-severe knee pain or frequent knee pain and longitudinally with frequent knee pain 2 years after the baseline evaluation.
  
  
  METHODS
  We studied 182 persons with knee OA (305 knees). Applying specialized magnetic resonance imaging techniques, manual segmentation was used to compute cartilage-covered and denuded bone areas for each surface. Moderate-to-severe knee pain was defined as a score of >or=40 mm on a knee-specific 100-mm visual analog scale, and frequent knee pain was defined as pain on most days during the past month. Logistic regression and generalized estimating equations were used in analyses, adjusting for age, sex, body mass index, and bone marrow lesions.
  
  
  RESULTS
  Cross-sectional analyses revealed that moderate-to-severe knee pain was associated with percent denuded bone in the medial compartment (adjusted odds ratio [OR] 3.90, 95% confidence interval [95% CI] 1.33-11.47), in the medial and patellar surfaces together, and in the lateral and patellar surfaces. Frequent knee pain was associated with percent denuded bone in the patellar surface (adjusted OR 3.11, 95% CI 1.24-7.81), in the medial and patellar surfaces, and in the lateral and patellar surfaces. Longitudinal analyses (in 168 knees without frequent knee pain at baseline) revealed that percent denuded bone in the medial and patellar surfaces was associated with frequent incident knee pain (adjusted OR 4.19, 95% CI 1.56-11.22).
  
  
  CONCLUSIONS
  These results support a relationship between subchondral bone plate exposure and prevalent and incident knee pain in patients with knee OA.
authors: Feinberg School of Medicine, Northwestern University, Chicago, Illinois 60611, USA.
authors: Kirsten
authors: K
authors: Moisio
authors: Felix
authors: F
authors: Eckstein
authors: Joan S
authors: JS
authors: Chmiel
authors: Ali
authors: A
authors: Guermazi
authors: Pottumarthi
authors: P
authors: Prasad
authors: Orit
authors: O
authors: Almagor
authors: Jing
authors: J
authors: Song
authors: Dorothy
authors: D
authors: Dunlop
authors: Martin
authors: M
authors: Hudelmaier
authors: Ami
authors: A
authors: Kothari
authors: Leena
authors: L
authors: Sharma
mesh_terms: D000368:Aged; D002358:Cartilage, Articular / Q000473:pathology*; D015331:Cohort Studies; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D020370:Osteoarthritis, Knee / Q000150:complications / Q000473:pathology* / Q000503:physiopathology; D010146:Pain / Q000209:etiology / Q000473:pathology* / Q000503:physiopathology; D057071:Patellofemoral Joint / Q000473:pathology* / Q000503:physiopathology; D013977:Tibia / Q000473:pathology* / Q000503:physiopathology