title: Quadriceps weakness, patella alta, and structural features of patellofemoral osteoarthritis.
abstract: OBJECTIVE
  To determine the relationship between quadriceps weakness and cartilage damage and bone marrow lesions (BMLs) in the patellofemoral joint (PFJ) and if this relationship is modified by patella alta.
  
  
  METHODS
  The Multicenter Osteoarthritis Study is a cohort study of persons ages 50-79 years with or at risk of knee osteoarthritis. Concentric knee extensor strength was measured using an isokinetic dynamometer. Patella alta was measured using the Insall-Salvati ratio (ISR) on the lateral radiograph, and cartilage damage and BMLs were graded on magnetic resonance imaging in the PFJ. We determined the association between quadriceps weakness with cartilage damage and BMLs in the PFJ among knees with (ISR ≥1.2) and without (ISR <1.2) patella alta using multiple binomial regression.
  
  
  RESULTS
  A total of 807 knees were studied (mean age 62 years, body mass index 30 kg/m(2) , ISR 1.10) and 64% were from women. Compared with the knees in the highest strength tertile, those in the lowest had 10.2% (95% confidence interval [95% CI] 3, 18), 9.1% (95% CI 2, 16), and 7.1% (95% CI 1, 13) higher prevalence of lateral PFJ cartilage damage, medial PFJ cartilage damage, and lateral PFJ BMLs, respectively. The association between quadriceps weakness with cartilage damage and BMLs was not different between knees with and without patella alta in the lateral PFJ.
  
  
  CONCLUSIONS
  Quadriceps weakness was associated with PFJ cartilage damage and BMLs. While both patella alta and quadriceps weakness were associated with PFJ damage, the combination of the two was not associated with more damage than either of these factors alone.
authors.affiliation: Boston University School of Medicine, Boston, Massachusetts 02118, USA. stefanik@bu.edu
authors.forename: Joshua J
authors.initials: JJ
authors.lastname: Stefanik
authors.forename: Ali
authors.initials: A
authors.lastname: Guermazi
authors.forename: Yanyan
authors.initials: Y
authors.lastname: Zhu
authors.forename: Ann C
authors.initials: AC
authors.lastname: Zumwalt
authors.forename: K Douglas
authors.initials: KD
authors.lastname: Gross
authors.forename: Margaret
authors.initials: M
authors.lastname: Clancy
authors.forename: John A
authors.initials: JA
authors.lastname: Lynch
authors.forename: Neil A
authors.initials: NA
authors.lastname: Segal
authors.forename: Cora E
authors.initials: CE
authors.lastname: Lewis
authors.forename: Frank W
authors.initials: FW
authors.lastname: Roemer
authors.forename: Christopher M
authors.initials: CM
authors.lastname: Powers
authors.forename: David T
authors.initials: DT
authors.lastname: Felson
mesh_terms: D000368:Aged; D000407:Alabama; D002358:Cartilage, Articular / Q000473:pathology; D005260:Female; D006801:Humans; D007484:Iowa; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D053580:Muscle Strength; D053581:Muscle Strength Dynamometer; D018908:Muscle Weakness / Q000209:etiology* / Q000473:pathology / Q000503:physiopathology; D020370:Osteoarthritis, Knee / Q000150:complications* / Q000473:pathology / Q000503:physiopathology; D010329:Patella / Q000000981:diagnostic imaging / Q000473:pathology*; D057071:Patellofemoral Joint / Q000473:pathology*; D052097:Quadriceps Muscle / Q000503:physiopathology*; D011859:Radiography; D012044:Regression Analysis; D018570:Risk Assessment; D012307:Risk Factors