title: Thigh muscle cross-sectional areas and strength in knees with early vs knees without radiographic knee osteoarthritis: a between-knee, within-person comparison.
abstract: OBJECTIVE
  To compare cross-sectional and longitudinal side-differences in thigh muscle anatomical cross-sectional areas (ACSAs), muscle strength, and specific strength (strength/ACSA), between knees with early radiographic change vs knees without radiographic knee osteoarthritis (RKOA), in the same person.
  
  
  METHODS
  55 (of 4796) Osteoarthritis Initiative (OAI) participants fulfilled the inclusion criteria of early RKOA in one limb (definite tibiofemoral osteophytes; no radiographic joint space narrowing [JSN]) vs no RKOA (no osteophyte; no JSN) in the contralateral limb. ACSAs of the thigh muscles and quadriceps heads were determined using axial MRIs at 33%/30% femoral length (distal to proximal). Isometric extensor and flexor muscle strength were measured (Good Strength Chair). Baseline quadriceps ACSA and extensor (specific) strength represented the primary analytic focus, and 2-year changes of quadriceps ACSAs the secondary focus.
  
  
  RESULTS
  No statistically significant side-differences in quadriceps (or other thigh muscle) ACSAs, muscle strength, or specific strength were observed between early RKOA vs contralateral limbs without RKOA (P ≥ 0.44), neither in men nor in women. The 2-year reduction in quadriceps ACSA in limbs with early RKOA was -0.9 ± 6% (mean ± standard deviation) vs -0.5 ± 6% in limbs without RKOA (statistical difference P = 0.85).
  
  
  CONCLUSIONS
  Our results do not provide evidence that early unilateral radiographic changes, i.e., presence of osteophytes, are associated with cross-sectional or longitudinal differences in quadriceps muscle status compared with contralateral knees without RKOA. At the stage of early unilateral RKOA there thus appears to be no clinical need for countervailing a potential dys-balance in quadriceps ACSAs and strength between both knees.
authors.affiliation: Institute of Anatomy, Paracelsus Medical University, Salzburg, Austria. Electronic address: anja.ruhdorfer@pmu.ac.at.
authors.forename: A S
authors.initials: AS
authors.lastname: Ruhdorfer
authors.affiliation: Institute of Anatomy, Paracelsus Medical University, Salzburg, Austria. Electronic address: torben.dannhauer@pmu.ac.at.
authors.forename: T
authors.initials: T
authors.lastname: Dannhauer
authors.affiliation: Institute of Anatomy, Paracelsus Medical University, Salzburg, Austria. Electronic address: wolfgang.wirth@pmu.ac.at.
authors.forename: W
authors.initials: W
authors.lastname: Wirth
authors.affiliation: Institute of Anatomy, Paracelsus Medical University, Salzburg, Austria. Electronic address: sebastian.cotofana@pmu.ac.at.
authors.forename: S
authors.initials: S
authors.lastname: Cotofana
authors.affiliation: Department of Radiology, Boston University School of Medicine, Boston, MA, USA. Electronic address: Frank.Roemer@klinikum-augsburg.de.
authors.forename: F
authors.initials: F
authors.lastname: Roemer
authors.affiliation: Department of Epidemiology & Biostatistics, University of California, San Francisco, CA, USA. Electronic address: MNevitt@psg.ucsf.edu.
authors.forename: M
authors.initials: M
authors.lastname: Nevitt
authors.affiliation: Institute of Anatomy, Paracelsus Medical University, Salzburg, Austria. Electronic address: felix.eckstein@pmu.ac.at.
authors.forename: F
authors.initials: F
authors.lastname: Eckstein
mesh_terms: D000368:Aged; D016022:Case-Control Studies; D018450:Disease Progression; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D053580:Muscle Strength; D018482:Muscle, Skeletal / Q000473:pathology / Q000503:physiopathology; D009929:Organ Size; D020370:Osteoarthritis, Knee / Q000150:complications / Q000473:pathology* / Q000503:physiopathology; D054850:Osteophyte / Q000000981:diagnostic imaging / Q000209:etiology; D052097:Quadriceps Muscle / Q000473:pathology* / Q000503:physiopathology; D011859:Radiography; D013848:Thigh
keywords: Cross-sectional area; Knee osteoarthritis; Magnetic resonance imaging; Muscle; Strength