[Neuromuscular and architectural alterations of the vastus lateralis muscle in elderly patients with unilateral knee osteoarthritis].
OBJECTIVE
The aim of this study was to determine the mechanisms involved in muscle weakness in elderly patients with unilateral knee osteoarthritis.


METHODS
We investigated 7 patients with unilateral knee osteoarthritis.


METHODS
We measured knee position sense and isometric maximal voluntary contraction (MVC) of the knee extensors. Electromyographic (EMG) measurement of biceps femoris (BF), rectus femoris (RF), vastus lateralis (VL) and vastus medialis (VM) involved different levels of contraction (25, 50, 75 and 100% MVC). Neuromuscular efficiency of quadriceps was also calculated (MVC/EMG). Ultrasonography was used to investigate the VL architectural parameters at the median part of the VL for different levels of contraction (25, 50, and 75% MVC). All tests were performed on the osteoarthritic and healthy knees.


RESULTS
The quadriceps MVC of the affected knee was reduced by 30%. The VL thickness of the affected knee was 10% smaller than that of the unaffected knee. VL activity seen on EMG did not differ between knees, but RF, VM and BF activity was greater in the unaffected than affected knee. Neuromuscular efficiency was higher (26%) in the unaffected knee. Knee position sense was reduced by 33% in the affected knee.


CONCLUSIONS
Quadriceps weakness associated with knee osteoarthritis seems to be related to changes in muscle rather than pennation angle and changes in fascicule length.
Mairet
S
S
Institut de myologie-AIM, groupe hospitalier de la Pitié-Salpêtrière, 83, boulevard de l'Hôpital, 75651 Paris cedex 13, France.
Maïsetti
O
O
Rolland
E
E
Portero
P
P
D000368:Aged; D004576:Electromyography; D005260:Female; D006801:Humans; D007537:Isometric Contraction / Q000502:physiology; D008297:Male; D018908:Muscle Weakness / Q000503:physiopathology; D018482:Muscle, Skeletal / Q000000981:diagnostic imaging / Q000503:physiopathology*; D020370:Osteoarthritis, Knee / Q000503:physiopathology*; D014463:Ultrasonography