The biomechanical changes in gait and posture as a result of the total knee arthroplasty

Abstract

Peat et al (2001) identified that 25% of the UK population suffers from knee pain, with 50% of this group being affected by knee osteoarthritis. Of this 50% of the population it has been suggested that 27.4 out of every 1000 knees are deemed suitable for replacement (arthroplasty). This study aimed to investigate the biomechanical and patient reported changes following total knee arthroplasty. A sample of 14 patients were recruited from the Lancashire Teaching Hospitals NHS Foundation trust all of who were diagnosed with tricompartmental osteoarthritis of the knee (K-L grade 2-4) and scheduled for the Zimmer NexGen CR total knee arthroplasty. The patients attended 4 assessments; preoperatively (baseline), six weeks, three months and six months postoperatively. At all assessments the patients performed three tasks, which were
steady state gait, gait initiation and quiet standing whilst their kinematics and kinetics were measured. At these assessments patients completed self-reported questionnaires.
Only 10 completed all assessments and were therefore considered in the final analysis. The results indicated that during quiet standing the coronal plane knee angle shifted alignment from varus to valgus (pc0.05), there was an increase in the sagittal plane knee moments (p<0.05), there was increased external rotation about the hip (pc0.05) and an increased flexion moment about the hip (pc0.05). In the gait initiation task the results indicated a shift in the coronal plane angle from varus to valgus (pc0.05) and an increase in the decouple vector between the centre of mass and the centre of pressure (pc0.05). Walking gait identified the greatest number of changes where the external rotation about the ankle increased (p<O.OS), the plantar and dorsiflexion moments about the ankle increased (pc0.05), the coronal plane angle about the knee shifted from varus to valgus (p.c0.05), the knee adduction moments decreased (pc0.05), the coronal plane range of motion about the hip decreased (pc0.05), the internal rotation moment about the knee decreased (pc0.05), the anterior and posterior ground reaction forces increased (pc0.05) and the walking velocity and step length both increased (pc0.05). The patient self-reported questionnaire identified subjective improvements in pain, a reduction of symptoms, improved ability to participate in activities of daily living, improved participation in sport and recreation and a general improvement in quality of life
(pc0.05). In conclusion, when successful the Zimmer NexGen total knee arthroplasty appears to significantly improve joint pain and function up to six months following postoperatively. A plateau effect was identified between six weeks and three months postoperatively, which may be partially due to the removal of walking aids.