EU Musc_Liikavainio_Layout 1 18/12/2009 10:22 Page 12
Osteoarthritis
Figure 1: Magnetic Resonance Image Assessment of the Cross-sectional Area of the Pelvic and Thigh Muscles
I III
I
II
III
IV
II IV
Figure 2: A Method for Determining Muscle Thickness
disuse atrophy of the muscles due to joint pain;
25,26
and Echogenicity from the Rectus Femoris and Vastus reflex inhibition of muscles moving the affected joint;
8,25–27
and
Intermedius of the Quadriceps Femoris Muscle
inability to fully activate the muscle resulting in the decreased
force production.
23,28,29
Knee joint laxity is also associated with a decrease in the magnitude
of the relationship between strength and physical function in knee
OA.
30
Assessment of weakness in the QFm has been shown to be a
better determinant of pain and disability than radiographic changes in
knee OA.
31–33
However, the ultimate mechanism behind the muscle
weakness in knee OA is not fully understood.
It has been claimed that a strong muscular system may prevent the
initiation and progression of OA, because it has been shown that
reduced quadriceps strength relative to bodyweight may be a risk
factor for knee OA in women.
1,2
However, QFm strength may be a
significant risk factor for radiographic progression of knee OA in
malaligned and lax knees; in other words, strength training may evoke
damage in at-risk OA knee joints.
34
Proprioception and Standing Balance
The neuromuscular system (NMS) allows finely controlled
movements, provides functional joint stability and gives sensory
RF = rectus femoris; VI = vastus intermedius.
information about limb position and movements, which constitute the
neuromuscular protective mechanisms that minimise adverse loading
suffering from knee and hip OA exhibit decreased strength in their during locomotion and prevent joint damage. The sensorimotor
pelvic and QF muscles.
1,8,10,20–24
Recently, we used maximal voluntary dysfunction that may occur due to ageing could play a significant role
isometric knee extension and flexion tests to demonstrate that knee in the pathogenesis and/or progression of hip and knee OA through
OA subjects have significantly lower knee extension and flexion the impairment in NMS-protective mechanisms, although there is a
isometric torques than corresponding age-matched healthy general assumption that joint damage precedes pain, disability and
controls
14
(see Figure 3). Knee extension or flexion torques did not muscle weakness.
35
diverge between knee OA severity subgroups, but the knee
extension torque exhibited a significant negative linear trend as the Muscle spindles, joint receptors and Golgi tendon organs are
severity of knee OA increased. proprioceptors, providing information about the position and
movement of the joint. If the sensitivity of proprioceptors is
Several mechanisms have been proposed to be involved in muscle diminished, their ability to detect and transfer information to the
weakness in OA: central nervous system (CNS) will be impaired. As a consequence, the
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