title: Weight-bearing asymmetry and vertical activity differences in a rat model of post-traumatic knee osteoarthritis.
abstract: OBJECTIVE
  This study used a rat model of post-traumatic knee osteoarthritis (OA) created by anterior cruciate ligament transection with partial medial meniscectomy (ACLT + pMMx). In this model, mild to moderate structural changes that are typical of knee OA have been observed within 2 and 8 weeks post-surgery. We aimed to determine whether pain-related behaviours can distinguish between an ACLT + pMMx and a sham surgery group.
  
  
  METHODS
  Three-month old male Sprague-Dawley rats underwent ACLT + pMMx on their right hindlimb within two groups of n = 6 each, and sham surgery within two groups of n = 5 each. Assessments evaluated percent ipsilateral weight-bearing for static weight-bearing and 18 different variables of exploratory motor behaviour at multiple time points between 1 and 8 weeks post-surgery. Histology was performed on the right hindlimbs at 4 and 8 weeks post-surgery.
  
  
  RESULTS
  Histology confirmed mild to moderate knee OA changes in the ACLT + pMMx group and the absence of knee OA changes in the sham group. Compared to the sham group, the ACLT + pMMx group had significantly lower percent ipsilateral weight-bearing from 1 through 8 weeks post-surgery. Compared to the sham group, the ACLT + pMMx group had significantly lower vertical activity (episode count, time, and count) values.
  
  
  CONCLUSIONS
  These findings suggest that ipsilateral weight-bearing deficit and vertical activity limitations resulted from the presence of knee OA-like changes in this model. When using the ACLT + pMMx-induced rat model of knee OA, percent ipsilateral weight-bearing and vertical activity distinguished between rats with and without knee OA changes. These variables may be useful outcome measures in preclinical research performed with this experimental post-traumatic knee OA model.
authors.affiliation: Graduate Program in Health and Rehabilitation Sciences, Faculty of Health Sciences, University of Western Ontario, London, ON, Canada; Collaborative Graduate Program in Musculoskeletal Health Research, University of Western Ontario, London, ON, Canada. Electronic address: chamil7@uwo.ca.
authors.forename: C B
authors.initials: CB
authors.lastname: Hamilton
authors.affiliation: Collaborative Graduate Program in Musculoskeletal Health Research, University of Western Ontario, London, ON, Canada; Department of Physiology and Pharmacology, Schulich School of Medicine and Dentistry, University of Western Ontario, London, ON, Canada. Electronic address: mpest@uwo.ca.
authors.forename: M A
authors.initials: MA
authors.lastname: Pest
authors.affiliation: Department of Physiology and Pharmacology, Schulich School of Medicine and Dentistry, University of Western Ontario, London, ON, Canada. Electronic address: vasek.pitelka@schulich.uwo.ca.
authors.forename: V
authors.initials: V
authors.lastname: Pitelka
authors.affiliation: Collaborative Graduate Program in Musculoskeletal Health Research, University of Western Ontario, London, ON, Canada; Department of Physiology and Pharmacology, Schulich School of Medicine and Dentistry, University of Western Ontario, London, ON, Canada. Electronic address: aratnesw@uwo.ca.
authors.forename: A
authors.initials: A
authors.lastname: Ratneswaran
authors.affiliation: Collaborative Graduate Program in Musculoskeletal Health Research, University of Western Ontario, London, ON, Canada; Department of Physiology and Pharmacology, Schulich School of Medicine and Dentistry, University of Western Ontario, London, ON, Canada. Electronic address: fbeier@uwo.ca.
authors.forename: F
authors.initials: F
authors.lastname: Beier
authors.affiliation: Graduate Program in Health and Rehabilitation Sciences, Faculty of Health Sciences, University of Western Ontario, London, ON, Canada; Collaborative Graduate Program in Musculoskeletal Health Research, University of Western Ontario, London, ON, Canada; School of Physical Therapy, Faculty of Health Science Department of Epidemiology and Biostatistics, Schulich School of Medicine and Dentistry, University of Western Ontario, London, ON, Canada. Electronic address: bcheswor@uwo.ca.
authors.forename: B M
authors.initials: BM
authors.lastname: Chesworth
mesh_terms: D000818:Animals; D000070598:Anterior Cruciate Ligament Injuries; D001169:Arthritis, Experimental / Q000209:etiology / Q000473:pathology / Q000503:physiopathology*; D001522:Behavior, Animal / Q000502:physiology; D002358:Cartilage, Articular / Q000473:pathology; D007718:Knee Injuries / Q000150:complications*; D007719:Knee Joint / Q000503:physiopathology*; D008297:Male; D009043:Motor Activity / Q000502:physiology; D020370:Osteoarthritis, Knee / Q000209:etiology / Q000473:pathology / Q000503:physiopathology*; D017207:Rats, Sprague-Dawley; D000070600:Tibial Meniscus Injuries; D016474:Weight-Bearing / Q000502:physiology*
keywords: Animal models; Anterior cruciate ligament; Behaviour; Osteoarthritis; Pain