Therapeutic cooling: No effect on hamstring reflexes and knee stability

Purpose: Stretch reflexes contribute to joint stiffness, but the effects of therapeutic cooling on these reflexes are unknown. Therapeutic cooling is frequently used in knee rehabilitation, for instance, after rupture of the anterior cruciate ligament. Cooling a joint can affect nerve conduction velocity and the function of sensory organs. Such changes in neuromuscular coupling could reduce knee stability and increase the risk of knee injury. The aim of the present study was to evaluate whether there are negative effects of knee cooling on the hamstring short and medium latency reflex responses or on the anterior tibia trajectory after mechanically induced tibia translation. Methods: In 15 healthy volunteers, the latency and size of short latency and medium latency reflex responses of hamstring muscles were assessed before and after 20 min of cold therapy of the knee joint as applied in rehabilitation. Reflex responses were evoked by a mechanically induced posterior-anterior tibia translation during standing. Reflexes were recorded by surface electromyography. The distance of anterior tibia motion and its velocity were assessed by potentiometric position transducer. Results: Local cold therapy of the knee did not alter the latency or the size of short or medium latency responses. Also, the extent and the velocity of tibia translation were unchanged after knee cooling. Conclusion: Cold therapy does not seem to adversely influence the spinal reflexes of the hamstrings induced by anterior tibia translation. As neuromuscular coupling was not significantly affected, the cold therapy, as performed in the present study, is not likely to increase the risk of knee injury.