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

1. The normal activity of the medial articular nerve of the knee joint of nine dogs was measured in response to continuous passive movement. Whole nerve recordings were made simultaneously with joint position and angular velocity. 2. When the knee was moved the medial articular nerve discharged at all joint angles with maximum activity at flexion in some animals, and at extension in others. For an individual animal the discharge pattern was reproducible over several cycles of movement. 3. The discharge was direction sensitive, responding with a lesser activity whenever the joint was moved away from the extremes of movement range. 4. With higher velocities of movement, the discharge activity of the nerve increased at the ends of joint movement. 5. The results indicate that the discharge activity of the whole medial articular nerve is influenced not only by joint position but also by the velocity and acceleration of movement. This may reflect changes in the tension of capsular and extra-capsular tissues.