title: Lifelong moderate running training increases the incidence and severity of osteoarthritis in the knee joint of C57BL mice.
abstract: BACKGROUND
  Inbred C57BL male mice express a high incidence of spontaneous osteoarthritis of the knee joint at the age of 18 months. We used this strain of mice to find out the effects of life-long, moderate running exercise on the health of articular cartilage and the incidence of osteoarthritis.
  
  
  METHODS
  Male mice (294) were divided into controls and runners. The runners were trained daily between 2 and 18 months of age. The speed was 13.3 m/min and the distance on a flatbelt treadmill was 1,000 m/day. The mice were sacrificed at the ages of 2, 6, 10, 14, and 18 months. The knee joints were sectioned in frontal direction and the osteoarthritic changes were graded using a conventional light microscope. The reproducibility of the grading method was tested by calculating the extended kappa-coefficient for the results of six researchers.
  
  
  RESULTS
  The incidence of osteoarthritis at the age of 18 months increased from 72% in controls to 88% in runners in the medial tibial condyles (P < 0.05), and from 80 to 96% in the lateral tibial condyles (P < 0.001). The incidence of the most severe osteoarthritic changes rose from 16% in controls to 36% in runners in the medial tibial condyles, and from 4 to 36% in the lateral tibial condyles.
  
  
  CONCLUSIONS
  According to our results, the moderate, long-lasting running exercise accelerates the development of osteoarthritis in the knee joints of C57BL mice.
authors.affiliation: Department of Anatomy, University of Kuopio, Finland.
authors.forename: T
authors.initials: T
authors.lastname: Lapveteläinen
authors.forename: T
authors.initials: T
authors.lastname: Nevalainen
authors.forename: J J
authors.initials: JJ
authors.lastname: Parkkinen
authors.forename: J
authors.initials: J
authors.lastname: Arokoski
authors.forename: K
authors.initials: K
authors.lastname: Kiraly
authors.forename: M
authors.initials: M
authors.lastname: Hyttinen
authors.forename: P
authors.initials: P
authors.lastname: Halonen
authors.forename: H J
authors.initials: HJ
authors.lastname: Helminen
mesh_terms: D000818:Animals; D002358:Cartilage, Articular / Q000473:pathology; D004195:Disease Models, Animal; D007719:Knee Joint / Q000473:pathology; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D010003:Osteoarthritis / Q000209:etiology* / Q000473:pathology; D010805:Physical Conditioning, Animal / Q000009:adverse effects*; D005082:Physical Exertion; D012420:Running