LOADING AND DEFORMATION OF THE CAT POSTERIOR KNEE-JOINT CAPSULE IN AXIAL AND EXTENSION ROTATIONS

Deformation and loading of the knee posterior joint capsule were studi ed in the cat, in extension rotations and in axial external(ER) and in ternal (IR) rotations at full extension. Loads were measured in the li gament along the upper edge of the capsule, using mechanically sensiti ve neurons that were calibrated as load cells. Strains were measured a cross the surface of the capsule, by tracking a set of markers attache d to its surface. External rotations produced small loads in the cable : with applied moments of up to 0.25 Nm, cable tensions were less than 0.8 mPa. The cable was not loaded by internal rotations. Axial rotati ons produced predominantly shear strains in the capsule. Extension pro duced small loads in the ligament and the predominant capsule strain w as tensile along the axis of the femur. These results show that the po sterior capsule has a small role in resisting extension, a minimal rol e in providing axial stability in ER, and no such role in IR.