Influence from stretch-sensitive receptors in the collateral ligaments of the knee joint on the gamma-muscle-spindle systems of flexor and extensor muscles.

In lightly alpha-chloralose anaesthetized cats, activity was recorded simultaneously from 2-4 primary muscle spindle afferents from triceps surae and/or posterior biceps and semitendinosus muscles. Increased tension in medial or lateral collateral ligament was found to evoke changes in the responses of the primary spindle afferents to sinusoidal stretching of their parent muscles. It is concluded that these changes were due to reflex actions of stretch/tension-sensitive receptors in the collateral ligaments on fusimotor neurones. Thus, receptor afferents from the collateral ligaments may contribute to the regulation of the activity in the gamma-motor-muscle-spindle system, and thereby also be of importance for the control of muscular stiffness and knee joint stability.