Muscle weakness causes joint degeneration in rabbits.
OBJECTIVE
The objective of this study was to investigate the effects of botulinum toxin type-A (BTX-A) induced quadriceps weakness on micro-structural changes in knee cartilage of New Zealand White (NZW) rabbits.


METHODS
Fifteen rabbits were divided randomly into an experimental and a sham control group. Each group received a unilateral single quadriceps muscle injection either with saline (sham control; n=4) or BTX-A (experimental; n=11).


RESULTS
BTX-A injection produced significant quadriceps muscle weakness (P<0.05) and loss of quadriceps muscle mass (P<0.05). Degenerative changes of the knee cartilage, assessed with the Mankin grading system, were the same for the injected and non-injected hind limbs of the experimental group animals. Sham injection had no effect on joint degeneration but all control animals showed some degenerative changes in the knee. Degenerative changes of the retro-patellar cartilage were more severe in the experimental compared to sham control group rabbits (P<0.05). The distal region of the retro-patellar cartilage was more degenerated than the proximal part in the experimental and control group rabbits (P<0.05). The Mankin grades for the tibiofemoral region were not significantly different between experimental and control group rabbits (P>0.05).


CONCLUSIONS
Quadriceps muscle weakness caused increased degeneration in the retro-patellar cartilage of NZW rabbits, providing evidence that muscle weakness might be a risk factor for the onset and progression of osteoarthritis (OA). Future work needs to delineate whether muscle weakness directly affects joint degeneration, or if changes in function and movement execution associated with muscle weakness are responsible for the increased rate of OA onset and progression observed here.
Human Performance Laboratory, Faculty of Kinesiology, University of Calgary, AB, Canada.
A
A
Rehan Youssef
D
D
Longino
R
R
Seerattan
T
T
Leonard
W
W
Herzog
D000818:Animals; D019274:Botulinum Toxins, Type A / Q000008:administration & dosage*; D002358:Cartilage, Articular / Q000187:drug effects / Q000503:physiopathology*; D004195:Disease Models, Animal; D005260:Female; D007593:Joint Instability / Q000503:physiopathology*; D007719:Knee Joint / Q000503:physiopathology*; D018908:Muscle Weakness / Q000139:chemically induced / Q000503:physiopathology*; D010003:Osteoarthritis / Q000209:etiology*; D052097:Quadriceps Muscle / Q000503:physiopathology; D011817:Rabbits; D011897:Random Allocation; D012307:Risk Factors
D019274:Botulinum Toxins, Type A