Dynamic in vivo kinematics of the intact ovine stifle joint.

The ovine stifle joint is a promising model for the investigation of joint mechanobiology in both normal and pathological states. The objectives of this study were to characterize three-dimensional (3D) joint motion in the intact ovine stifle joint during walking, incline walking, and trotting; to determine the range of variability in normal joint motion (intrasubject and intersubject); and to characterize the 3D ground reaction forces in the ovine hind limb during walking. 3D in vivo kinematics were measured in the right hind limb of eight sheep during walking, incline walking, and trotting on a treadmill (accuracy: 0.4 +/- 0.4 mm, 0.4 +/- 0.4 degrees). 3D ground reaction forces were measured in the hind limbs of the same subjects during walking. Joint flexion ranged from 43.1 to 77.0 degrees, and was coupled with abduction (0.0-4.1 degrees ), internal rotation (5.9-17.6 degrees), and translations in the medial (5.1-7.3 mm), anterior (21.9-23.8 mm), and superior (6.0-11.4 mm) directions. Kinematics were similar during walking, incline walking, and trotting. Intrasubject variability was small, ranging from 0.4-2.0 degrees for rotations, and 0.4-0.5 mm for translations. The active range of joint motion was offset between subjects leading to intersubject variability of 4.1-7.4 degrees for rotations and 2.5-4.2 mm for translations. Peak vertical ground reaction forces in the hind limbs ranged from 34.5(+/-1.6) to 50.0(+/-5.6)% body weight. This study establishes the bounds of normal motion in the intact ovine stifle joint and provides baseline data for further studies of joint mechanobiology in this model.