Pressure‐volume relationships and elastance in the knee joint of the dog.

Abstract

SUMMARY1. This study has investigated changes in intra-articular hydrostatic pressure in the knee joints of normal dogs in response to continuous and stepwise infusions of fluids. The relationship between pressure and volume in the joint was examined over the pressure range of -8 to +50 mmHg, and also at much higher pressures often associated with joint disease or injury. The effects of joint angle and dog weight on the pressure-volume relationship and on elastance of the dogs' knees were also examined.2. With liquid paraffin B.P. the pressure was found to increase more with each unit volume infused at subatmospheric pressures than at pressures around atmospheric, and increased more again at higher pressures. The pressure-volume curve with saline infusions was affected by egress of fluid from the joint at supra-atmospheric pressure. Above + 5 mmHg the rise in pressure per unit volume infused was less than that for paraffin at the same volume.3. Elastance and compliance of the normal joint capsule were calculated from the pressure-volume data. Elastance was high at subatmospheric pressures, decreased rapidly as atmospheric pressure was approached and rose as a linear function of pressure above 12 mmHg.4. The biphasic shape ofthe elastance-pressure curve is discussed, and explanations for the shape are suggested.5. After intra-articular pressure in the knee was raised by infusion of paraffin oil the joint was moved through the range of positions from 125 deg extension to 50 deg flexion. Intra-articular pressure did not change across the range 125-110 deg. However, increasing the angle of flexion from 110 to 50 deg resulted in a rise in pressure which became steeper for each volume increment.6. Increasing intra-articular fluid volume caused a decrease in the total range of movement of the joint.7. The pressure-volume curves measured at extended angles of 110, 125 and 140 deg, where the starting pressures were subatmospheric, were the same. At flexed joint positions of 80 and 50 deg, where the starting pressures were supra-atmospheric, the pressure-volume curves became steeper with greater flexion. * Authors names are in alphabetical order.14 pHY 357S. NADE AND P. J. NEWBOLD 8. Elastance of the joint tissues increased with flexion. The elastance at each joint angle depended also on the volume or pressure.9. Significant differences were found to exist between pressure-volume curves for three groups of animals of different weight. Curves were steeper in small animals.10. Acrylic casts of the knee joint space were constructed at 90 and 40 deg of flexion to demonstrate channels of communication between anterior and posterior regions. The anterior compartment provided two-thirds of the total surface area.

The interrelation of neural discharge, intra‐articular pressure, and joint angle in the knee of the dog.

“…4 min after the infusion the discharge rate had dropped back to its original level before infusion. The corresponding pressure response was typical of that observed in a previous investigation (Nade & Newbold, 1984 Figs. 1 and 3, there was only a small initial increase in discharge rate on infusion, and this declined rapidly, returning to the original pre-infused level 1 min after infusion.…”

Aspects of the pathogenesis of podal arthritis of the horse as an important part of navicular syndrome

“…Bei subatmosphäri-schen Drücken im Gelenk ist die Elastizität der Gelenkkapsel hoch. Schon in atmosphärischen Druckbereichen nimmt die Elastizität der Gelenkkapsel ab (Knight und Levick 1981, Nade und Newbold 1984.…”

The effects of direction and acceleration of movement of the knee joint of the dog on medial articular nerve discharge.

“…The animal was placed in the supine position and secured to the experimental table by fixing the bone screws to a metal scaffolding attached to the table by magnets. This enabled each femur to 507 S. NADE, P. J. NEWBOLD AND S. F. STRAFACE be positioned vertically, perpendicular to the table top and the dog's body, providing a fixed axis about which the knee joint could be freely moved (Nade & Newbold, 1984).…”

“…Rapid recovery of the elastic elements of the joint capsule, culminating in lesser tension exerted on the joint stretch receptors could have accounted for this. Nade & Newbold (1984) have shown that the elastance of a joint capsule is variable and that it is dependent upon the position of the joint as well as upon the intra-articular pressure and contained fluid volume.…”