Abstract
Pain is the principal symptom in knee pathologies and reduced muscle strength is a
common observation among knee patients. However, the relationship between knee joint
pain and muscle strength remains to be clarified. This study aimed at investigating
the changes in knee muscle strength following experimental knee pain in healthy volunteers,
and if these changes were associated with the pain intensities. In a crossover study,
18 healthy subjects were tested on 2 different days. Using an isokinetic dynamometer,
maximal muscle strength in knee extension and flexion was measured at angular velocities
0, 60, 120, and 180 degrees/second, before, during, and after experimental pain induced
by injections of hypertonic saline into the infrapatellar fat pad. On a separate day,
isotonic saline injections were used as control condition. The pain intensity was
assessed on a 0- to 100-mm visual analogue scale. Knee pain reduced the muscle strength
by 5 to 15% compared to the control conditions (P < .001) in both knee extension and flexion at all angular velocities. The reduction
in muscle strength was positively correlated to the pain intensity. Experimental knee
pain significantly reduced knee extension and flexion muscle strength indicating a
generalized muscle inhibition augmented by higher pain intensities.
Perspective
This study showed that knee joint pain has a significant impact on muscle function.
The findings provide evidence of a direct inhibition of muscle function by joint pain,
implying that rehabilitative strengthening exercises may be antagonized by joint pain.
Key words
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Article info
Publication history
Published online: December 13, 2010
Accepted:
September 26,
2010
Received in revised form:
September 8,
2010
Received:
May 5,
2010
Footnotes
Supported by grants from The Oak Foundation and The Association of Danish Physiotherapists Research Foundation, and The Association of Danish Physiotherapists Practice Foundation.
The authors have no conflicts of interest regarding this article.
Identification
Copyright
© 2011 American Pain Society. Published by Elsevier Inc. All rights reserved.
