title: Experimental quadriceps muscle pain impairs knee joint control during walking.
abstract: 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.
authors.affiliation: Clinical Motor Function Laboratory, Parker Institute, Frederiksberg Hospital, Ndr. Fasanvej 57, DK 2000 Frederiksberg, Denmark. marius.henriksen@frh.regionh.dk
authors.forename: Marius
authors.initials: M
authors.lastname: Henriksen
authors.forename: Tine
authors.initials: T
authors.lastname: Alkjaer
authors.forename: Hans
authors.initials: H
authors.lastname: Lund
authors.forename: Erik B
authors.initials: EB
authors.lastname: Simonsen
authors.forename: Thomas
authors.initials: T
authors.lastname: Graven-Nielsen
authors.forename: Bente
authors.initials: B
authors.lastname: Danneskiold-Samsøe
authors.forename: Henning
authors.initials: H
authors.lastname: Bliddal
mesh_terms: D000328:Adult; D001696:Biomechanical Phenomena; D018592:Cross-Over Studies; D004576:Electromyography; D005260:Female; D005684:Gait; D006801:Humans; D007273:Injections, Intramuscular; D007552:Isotonic Solutions / Q000008:administration & dosage; D007593:Joint Instability; D007719:Knee Joint / Q000503:physiopathology*; D008297:Male; D009048:Motor Skills; D009135:Muscular Diseases / Q000139:chemically induced / Q000503:physiopathology*; D010146:Pain / Q000139:chemically induced / Q000503:physiopathology*; D010147:Pain Measurement; D052097:Quadriceps Muscle / Q000503:physiopathology*; D012107:Research Design; D012462:Saline Solution, Hypertonic / Q000008:administration & dosage; D012965:Sodium Chloride / Q000008:administration & dosage; D016138:Walking
chemical_list: D007552:Isotonic Solutions; D012462:Saline Solution, Hypertonic; D012965:Sodium Chloride