title: Intra-articular anesthesia and knee muscle response.
abstract: BACKGROUND
  Many receptors located within the intra-articular knee structures contribute to the neuromuscular responses of the knee. The purpose was to compare the automatic postural response induced by a perturbation at the foot before and after an intra-articular injection of a local anesthetic (bupivicaine), after a saline (sham) injection, and after no intra-articular injection (control) in the knee.
  
  
  METHODS
  Muscle onset latencies and automatic response magnitudes for the vastus medialis, vastus lateralis, biceps femoris, medial hamstrings, tibialis anterior, and gastrocnemius were measured using electromyography (EMG) when anteriorly directed perturbations were applied to the feet of 30 subjects. All subjects then received a lidocaine skin injection followed by: an intra-articular bupivicaine injection (treatment group); an intra-articular saline injection (sham group); or no injection (control group), depending on their randomized group assignment. The perturbation tests were then repeated.
  
  
  RESULTS
  Muscle onset latencies and automatic response magnitudes did not change as a result of the intra-articular injections. Latencies were significantly greater for the vastus medialis and vastus lateralis when compared to the medial hamstrings, biceps femoris and tibialis anterior (P<0.001). Automatic response magnitudes for the tibialis anterior were significantly greater than those of the hamstrings, which were greater than those of the quadriceps (P<0.001).
  
  
  CONCLUSIONS
  There were no differences in muscle response when anteriorly directed perturbations were applied to the foot with or without an injection of local anesthetic in the knee. Intra-articular receptors were either unaffected by the anesthetic or the extra-articular receptors or receptors of the other joints were able to compensate for their loss.
authors.affiliation: Bioengineering Labs, Department of Orthopaedic Research, Brown Medical School, Providence, RI, USA.
authors.forename: Heidi L
authors.initials: HL
authors.lastname: Oksendahl
authors.forename: Braden C
authors.initials: BC
authors.lastname: Fleming
authors.forename: Peter R
authors.initials: PR
authors.lastname: Blanpied
authors.forename: Mark
authors.initials: M
authors.lastname: Ritter
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Hulstyn
authors.forename: Paul D
authors.initials: PD
authors.lastname: Fadale
mesh_terms: D000293:Adolescent; D000328:Adult; D000779:Anesthetics, Local / Q000008:administration & dosage; D002045:Bupivacaine / Q000008:administration & dosage*; D005260:Female; D006801:Humans; D007270:Injections, Intra-Articular; D007719:Knee Joint / Q000187:drug effects / Q000294:innervation* / Q000502:physiology*; D008297:Male; D008875:Middle Aged; D009119:Muscle Contraction / Q000187:drug effects / Q000502:physiology*; D018482:Muscle, Skeletal / Q000187:drug effects / Q000294:innervation* / Q000502:physiology*; D011930:Reaction Time / Q000502:physiology / Q000528:radiation effects; D012018:Reflex / Q000502:physiology* / Q000528:radiation effects
chemical_list: D000779:Anesthetics, Local; D002045:Bupivacaine