title: Interaction between gastrocnemius muscle weakness and moderate exercise deteriorates joint integrity in rat knee.
abstract: The aim of this study was to determine the effect on the knee joint of the interaction between ankle muscle weakness and moderate exercise. Gastrocnemius muscle weakness was induced by intramuscular injection of botulinum toxin type A (BTX) in rats. Low-speed treadmill running (12 m/min for 60 min) was applied for 6 weeks in rats with and without BTX. Untreated animals were used as controls. After BTX injection, the gastrocnemius muscle weakness was confirmed by 3-D motion analysis in kinematic features of the hindlimb during locomotion as an increased maximal dorsiflexion angle during the stance phase. Serum biomarker analysis by enzyme-linked immunosorbent assay revealed that low-speed running decreased the catabolic effect on type II collagen. However, the inhibition of catabolism induced by running exercise was significantly counteracted by BTX injection. In addition, thinning of the cartilage layer and a reduction in the chondrocyte density was also found in the tibial plateau of the knee in the BTX-injected rats after running for 6 weeks. These data suggest that moderate exercise have a positive effect on joint homeostasis. However, ankle muscle weakness may alter the mechanical environment of the knee and impair the integrity of joint cartilage with moderate exercise.
authors.affiliation: Department of Rehabilitation, Faculty of Rehabilitation, Hiroshima International University, Hiroshima, Japan.
authors.forename: J
authors.initials: J
authors.lastname: Ozawa
authors.forename: A
authors.initials: A
authors.lastname: Kaneguchi
authors.forename: R
authors.initials: R
authors.lastname: Tanaka
authors.forename: S
authors.initials: S
authors.lastname: Kawamata
authors.forename: T
authors.initials: T
authors.lastname: Kurose
authors.forename: H
authors.initials: H
authors.lastname: Moriyama
authors.forename: N
authors.initials: N
authors.lastname: Kito
authors.forename: N
authors.initials: N
authors.lastname: Kawaguchi
authors.forename: N
authors.initials: N
authors.lastname: Matsuura
mesh_terms: D000818:Animals; D000842:Ankle / Q000503:physiopathology; D001696:Biomechanical Phenomena; D019274:Botulinum Toxins, Type A / Q000633:toxicity; D002358:Cartilage, Articular / Q000473:pathology; D024043:Collagen Type II / Q000378:metabolism; D018908:Muscle Weakness / Q000139:chemically induced / Q000378:metabolism / Q000503:physiopathology*; D018482:Muscle, Skeletal / Q000503:physiopathology*; D009465:Neuromuscular Agents / Q000633:toxicity; D010805:Physical Conditioning, Animal / Q000502:physiology*; D051381:Rats; D013264:Stifle / Q000503:physiopathology*
chemical_list: D024043:Collagen Type II; D009465:Neuromuscular Agents; D019274:Botulinum Toxins, Type A
keywords: Articular cartilage; botulinum toxin type A; the gastrocnemius muscle; treadmill running; type II collagen