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Experimental quadriceps muscle pain impairs knee joint control during walking

¹Clinical Motor Function Laboratory, Parker Institute, Frederiksberg Hospital, Frederiksberg; ²Institute of Medical Anatomy Section C, Panum Institute, University of Copenhagen, Copenhagen N; and ³Center for Sensory-Motor Interaction, Laboratory for Experimental Pain Research, Aalborg University, Aalborg East, Denmark

Submitted 2 October 2006 ; accepted in final form 7 April 2007

Pain is a cardinal symptom in musculoskeletal diseases involving the knee joint, and aberrant movement patterns and motor control strategies are often present in these patients. However, the underlying neuromuscular mechanisms linking pain to movement and motor control are unclear. To investigate the functional significance of muscle pain on knee joint control during walking, three-dimensional gait analyses were performed before, during, and after experimentally induced muscle pain by means of intramuscular injections of hypertonic saline (5.8%) into vastus medialis (VM) muscle of 20 healthy subjects. Isotonic saline (0.9%) was used as control. Surface electromyography (EMG) recordings of VM, vastus lateralis (VL), biceps femoris, and semitendinosus muscles were synchronized with the gait analyses. During experimental muscle pain, the loading response phase peak knee extensor moments were attenuated, and EMG activity in the VM and VL muscles was reduced. Compressive forces, adduction moments, knee joint kinematics, and hamstring EMG activity were unaffected by pain. Interestingly, the observed changes persisted when the pain had vanished. The results demonstrate that muscle pain modulated the function of the quadriceps muscle, resulting in impaired knee joint control and joint instability during walking. The changes are similar to those observed in patients with knee pain. The loss of joint control during and after pain may leave the knee joint prone to injury and potentially participate in the chronicity of musculoskeletal problems, and it may have clinically important implications for rehabilitation and training of patients with knee pain of musculoskeletal origin.

experimental muscle pain; motor function; motor control; gait

This article has been cited by other articles:

				M Henriksen, T Alkjaer, E B Simonsen, and H Bliddal Experimental muscle pain during a forward lunge -- the effects on knee joint dynamics and electromyographic activity Br. J. Sports Med., July 1, 2009; 43(7): 503 - 507. [Abstract] [Full Text] [PDF]