Possible effects of mobilisation on acute post-operative pain and nociceptive function after total knee arthroplasty

Experimental studies in animals, healthy volunteers, and patients with chronic pain suggest exercise to provide analgesia in several types of pain conditions and after various nociceptive stimuli. To our knowledge, there is no data on the effects of exercise on pain and nociceptive function in surgical patients despite early mobilisation being an important factor to enhance recovery. We therefore investigated possible effects of mobilisation on post-operative pain and nociceptive function after total knee arthroplasty (TKA).

Thirty patients undergoing TKA under standardised anaesthesia and analgesia underwent an exercise (mobilisation) strategy on the first post-operative morning consisting of 25-m walking twice, with a 20-min interval. Pain was assessed at rest and during passive hip and knee flexion before, and 5 and 20 min after walk, as well as during walk. Nociceptive function (pain threshold and tolerance) was assessed with pressure algometry and an electrical stimulus.

Pain at rest (supine) and during hip and knee flexion was significantly reduced 5 min (P < 0.03) and 20 min (P < 0.003) after walk compared with before walk, and pain was reduced during the second walk compared with the first walk (P < 0.034). Knee pain pressure threshold (P = 0.002) but not tolerance (P = 0.27) was increased following walk compared with before walk.

This first exploratory hypothesis-generating pilot study suggests mobilisation to promote analgesic effects after TKA calling for future studies with a randomised, controlled design on exercise dose-response effects in post-surgical patients.