title: Age-related changes in strength, joint laxity, and walking patterns: are they related to knee osteoarthritis?
abstract: OBJECTIVE
  Aging is associated with musculoskeletal changes and altered walking patterns. These changes are common in people with knee osteoarthritis (OA) and may precipitate the development of OA. We examined age-related changes in musculoskeletal structures and walking patterns to better understand the relationship between aging and knee OA.
  
  
  METHODS
  Forty-four individuals without OA (15 younger, 15 middle-aged, 14 older adults) and 15 individuals with medial knee OA participated. Knee laxity, quadriceps femoris muscle strength (force-generating capacity), and gait were assessed.
  
  
  RESULTS
  Medial laxity was greater in the OA group, but there were no differences between the middle-aged and older control groups. Quadriceps femoris strength was less in the older control group and in the OA group. During the stance phase of walking, the OA group demonstrated less knee flexion and greater knee adduction, but there were no differences in knee motion among the control groups. During walking, the older control group exhibited greater quadriceps femoris muscle activity and the OA group used greater muscle co-contraction.
  
  
  CONCLUSIONS
  Although weaker, the older control group did not use truncated motion or higher co-contraction. The maintenance of movement patterns that were similar to the subjects in the young control group may have helped to prevent development of knee OA. Further investigation is warranted regarding age-related musculoskeletal changes and their influence on the development of knee OA.
authors.affiliation: Department of Physical Therapy and Program in Biomechanics and Movement Science, University of Delaware, 301 McKinly Lab, Newark, DE 19716, USA. krudolph@udel.edu
authors.forename: Katherine S
authors.initials: KS
authors.lastname: Rudolph
authors.forename: Laura C
authors.initials: LC
authors.lastname: Schmitt
authors.forename: Michael D
authors.initials: MD
authors.lastname: Lewek
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000375:Aging / Q000502:physiology*; D001696:Biomechanical Phenomena; D016022:Case-Control Studies; D004576:Electromyography; D005260:Female; D005684:Gait / Q000502:physiology*; D006801:Humans; D007593:Joint Instability / Q000503:physiopathology*; D007719:Knee Joint / Q000000981:diagnostic imaging / Q000503:physiopathology*; D008297:Male; D008875:Middle Aged; D009119:Muscle Contraction / Q000502:physiology; D053580:Muscle Strength / Q000502:physiology*; D020370:Osteoarthritis, Knee / Q000503:physiopathology*; D011859:Radiography; D016138:Walking / Q000502:physiology