title: Thigh muscle cross-sectional areas and strength in advanced versus early painful osteoarthritis: an exploratory between-knee, within-person comparison in osteoarthritis initiative participants.
abstract: OBJECTIVE
  To compare cross-sectional and longitudinal side differences in thigh muscle anatomic cross-sectional areas (ACSAs), strength, and specific strength (strength/ACSA) between knees with early versus advanced painful radiographic osteoarthritis in the same person.
  
  
  METHODS
  Forty-four of 2,678 Osteoarthritis Initiative participants (31 women and 13 men) met the inclusion criteria of bilateral frequent knee pain, medial joint space narrowing (JSN) in 1 knee, and no medial (or lateral) JSN in the contralateral knee. Thigh muscle ACSAs of the quadriceps, hamstrings, adductors, and individual quadriceps heads at consistent locations were determined using magnetic resonance imaging. Isometric muscle strength was determined in extension/flexion (Good Strength Chair). Baseline quadriceps ACSAs and strength were considered primary end points, and longitudinal changes of these factors were considered secondary end points (by paired t-tests).
  
  
  RESULTS
  No significant side differences in quadriceps (or other thigh muscle) ACSAs, strength, or specific strength were observed between medial JSN knees versus knees without JSN, or between specific medial JSN knee strata and contralateral knees without JSN, either in men or women. Two-year longitudinal changes in thigh muscle ACSAs and strength were small (≤5.2%) and did not differ significantly between medial JSN knees and knees without JSN.
  
  
  CONCLUSIONS
  In the context of previous findings that side differences in pain are associated with side differences in quadriceps ACSAs, the current results suggest that quadriceps (and other thigh muscle) properties are not independently associated with radiographic disease status (JSN) once knees have reached frequent pain status. Further, our longitudinal findings indicate that a more advanced radiographic stage of knee osteoarthritis is not necessarily associated with a longitudinal decline in muscle function.
authors: Paracelsus Medical University, A5020 Salzburg, Austria. anja.ruhdorfer@pmu.ac.at
authors: Anja
authors: A
authors: Ruhdorfer
authors: Torben
authors: T
authors: Dannhauer
authors: Wolfgang
authors: W
authors: Wirth
authors: Wolfgang
authors: W
authors: Hitzl
authors: C Kent
authors: CK
authors: Kwoh
authors: Ali
authors: A
authors: Guermazi
authors: David J
authors: DJ
authors: Hunter
authors: Olivier
authors: O
authors: Benichou
authors: Felix
authors: F
authors: Eckstein
mesh_terms: D000368:Aged; D018771:Arthralgia / Q000175:diagnosis / Q000209:etiology*; D005260:Female; D006801:Humans; D007537:Isometric Contraction; D007719:Knee Joint / Q000000981:diagnostic imaging; D008137:Longitudinal Studies; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D053580:Muscle Strength; D020370:Osteoarthritis, Knee / Q000150:complications* / Q000473:pathology / Q000503:physiopathology; D010147:Pain Measurement; D011379:Prognosis; D052097:Quadriceps Muscle / Q000473:pathology* / Q000503:physiopathology*; D011859:Radiography; D013997:Time Factors