title: Spatiotemporal gait compensations following medial collateral ligament and medial meniscus injury in the rat: correlating gait patterns to joint damage.
abstract: BACKGROUND
  After transection of the medial collateral ligament and medial meniscus (MCLT + MMT) in the rat, focal cartilage lesions develop over 4-6 weeks; however, sham surgery (MCLT alone) does not result in cartilage damage over a similar period. Thus, comparison of MCLT + MMT with the MCLT sham group offers an opportunity to investigate behavioral modifications related to focal cartilage and meniscus damage in the rat.
  
  
  METHODS
  MCLT or MCLT + MMT surgery was performed in the right knees of male Lewis rats, with spatiotemporal gait patterns and hind limb sensitivity assessed at 1, 2, 4, and 6 weeks postsurgery (n = 8 rats per group per time point, n = 64 total). After the animals were euthanized, Histology was performed to assess joint damage.
  
  
  RESULTS
  MCLT + MMT animals had unilateral gait compensations at early time points, but by week 6 bilateral gait compensations had developed in both the MCLT sham and MCLT + MMT groups. Conversely, heightened tactile sensitivity was detected in both MCLT sham and MCLT + MMT animals at week 1, but only the MCLT + MMT animals maintained heightened sensitivity to week 6. Cartilage lesions were found in the MCLT + MMT group but not in the MCLT sham group. Correlations could be identified between joint damage and gait changes in MCLT + MMT animals; however, the same gait changes were found with MCLT sham animals despite a lack of joint damage.
  
  
  CONCLUSIONS
  Combined, our data highlight a common conundrum in osteoarthritis (OA) research: Some behavioral changes correlate to cartilage damage in the OA group, but the same changes can be identified in non-OA controls. Of the behavioral changes detected, allodynia was maintained in MCLT + MMT animals but not in the MCLT sham group. However, the correlation between cartilage damage and hind limb sensitivity is relatively weak (R = -0.4498), and the range of sensitivity measures overlaps between groups. The factors driving gait abnormalities in MCLT and MCLT + MMT animals also remain uncertain. The gait modifications are similar between groups and do not appear until weeks after surgery, despite cartilage damage being focused in the MCLT + MMT group. Combined, our data highlight the need to evaluate the links between noncartilage changes and behavioral changes following joint injury in the rat.
authors.affiliation: J. Crayton Pruitt Family Department of Biomedical Engineering, University of Florida, 1275 Center Drive, Biomedical Sciences Building JG56, Gainesville, FL, 32610, USA. hkloefkorn@ufl.edu.
authors.forename: Heidi E
authors.initials: HE
authors.lastname: Kloefkorn
authors.affiliation: J. Crayton Pruitt Family Department of Biomedical Engineering, University of Florida, 1275 Center Drive, Biomedical Sciences Building JG56, Gainesville, FL, 32610, USA. starjacobs@ufl.edu.
authors.forename: Brittany Y
authors.initials: BY
authors.lastname: Jacobs
authors.affiliation: J. Crayton Pruitt Family Department of Biomedical Engineering, University of Florida, 1275 Center Drive, Biomedical Sciences Building JG56, Gainesville, FL, 32610, USA. nigiri1000@gmail.com.
authors.forename: Ayomiposi M
authors.initials: AM
authors.lastname: Loye
authors.affiliation: J. Crayton Pruitt Family Department of Biomedical Engineering, University of Florida, 1275 Center Drive, Biomedical Sciences Building JG56, Gainesville, FL, 32610, USA. kyle.allen@bme.ufl.edu.|Institute of Cellular Engineering and Regenerative Medicine, University of Florida, Gainesville, FL, USA. kyle.allen@bme.ufl.edu.|Nanoscience Institute for Medical and Engineering Technology, University of Florida, Gainesville, FL, USA. kyle.allen@bme.ufl.edu.|Pain Research and Intervention Center of Excellence, University of Florida, Gainesville, FL, USA. kyle.allen@bme.ufl.edu.
authors.forename: Kyle D
authors.initials: KD
authors.lastname: Allen
mesh_terms: D000818:Animals; D002358:Cartilage, Articular / Q000473:pathology; D004195:Disease Models, Animal; D005684:Gait / Q000502:physiology; D007794:Lameness, Animal / Q000209:etiology*; D008297:Male; D017888:Medial Collateral Ligament, Knee / Q000293:injuries*; D010003:Osteoarthritis / Q000473:pathology; D051381:Rats; D011917:Rats, Inbred Lew; D000070600:Tibial Meniscus Injuries