The effects of tendon vibration on quadriceps muscle activation in anterior cruciate ligament reconstructed and arthritic populations.

INTERVENTION: Part A. 15 ACL reconstructed and 15 age and gender matched controls and 15 subjects with knee osteoarthritis and 15 age and gender matched controls will have their infrapatellar tendon vibrated (50Hz) for 20 minutes while seated in a chair. Three maximum voluntary contractions of the quadriceps and three maximum voluntary contractions of the hamstrings will be performed before and then again after vibration. Part B. 3‐7 days later, the same subjects will have their infrapatellar tendon vibrated at 4 different frequencies (0Hz, 5Hz, 80Hz, 200Hz) during maximum voluntary contractions of their quadriceps. Three maximum voluntary contractions will be performed at each frequency, in a random order. A 2 minute rest period will be given between each contraction. CONDITION: Anterior cruciate ligament (ACL) reconstruction Knee osteoarthritis PRIMARY OUTCOME: Normalised quadriceps peak torque (Newton metres/Body weight) SECONDARY OUTCOME: Normalised peak hamstrings torque (Newton metres/body weight) Root mean square of electromyographic signals recorded from the quadriceps and hamstrings muscles INCLUSION CRITERIA: Participants in the ACL reconstructed group should have had an ACL reconstruction in the last 4‐24 months using a semitendinosus gracilis graft. Participants in the osteoarthritis group will have radiologically diagnosed osteoarthritis of the knee with a kellgren lawrence score of greater than or equal to 2.