title: Pressures in normal and acutely distended human knee joints and effects on quadriceps maximal voluntary contractions.
abstract: Pressures were recorded in ten knees from five subjects with informed consent. Resting intra-articular pressures were found to be sub-atmospheric with a mean value of -5 +/- 1.5 mmHg (S.E. of mean). There was little variation in intra-articular pressure with changing joint angle in the normal joint. Infusion of as small a volume as 5 ml of sterile saline into the joint cavity caused the intra-articular pressure to increase to supra-atmospheric levels. Changing joint angle now produced clear modulations in intra-articular pressure. Pressure increased as the limb was moved out to extension and back to flexion with a minimum occurring in the mid-range. These modulations were more pronounced with active positioning of the joint than with passive positioning. Successive increases in intra-articular volume produced increases in intra-articular pressure as well as the degree of modulation of intra-articular pressure with joint angle. Cyclical flexion-extension movements caused a progressive decrease in the maximum pressure observed in extension. Non-noxious distension of the knee joint caused substantial reductions in the magnitude of isometric and isokinetic maximal voluntary contractions of quadriceps due to a reflex inhibition from joint mechanoreceptor afferents.
authors.affiliation: Institute of Physiology, University, Glasgow.
authors.forename: L
authors.initials: L
authors.lastname: Wood
authors.forename: W R
authors.initials: WR
authors.lastname: Ferrell
authors.forename: R H
authors.initials: RH
authors.lastname: Baxendale
mesh_terms: D004576:Electromyography; D006801:Humans; D007719:Knee Joint / Q000502:physiology*; D009119:Muscle Contraction; D009132:Muscles / Q000502:physiology*; D011312:Pressure; D013314:Stress, Mechanical