Swing phase kinetics and kinematics of knee replacement patients during obstacle avoidance Jeannette M. Byrne, Stephen D. Prentice * Gait and Posture Laboratory, Department of Kinesiology, University of Waterloo, 200 University Avenue West, Waterloo, Ont., Canada N2L 3G1 Accepted 17 September 2002 Abstract Proper knee joint function is essential for safe and effective mobility within a complex environment. Following knee joint replacement, joint structure and function are altered, often requiring individuals to adjust normal movement patterns in order to adapt to these changes. Such adaptations may either improve function or lead to movement patterns that may potentially be unsafe for individuals. To investigate this issue, a group of individuals who had undergone knee replacement was examined while performing an obstacle avoidance task. Their performance was compared with that of healthy age-matched controls. Participants walked along a 10 m walkway a total 48 times. Trials were divided equally between unobstructed walking and clearing a 6 or 18 cm obstacle during both right and left limb lead. Lead limb kinetic and kinematic variables were examined and revealed that members of the surgical group exhibited decreased active surgical knee flexion and diminished surgical knee flexor work. In order to maintain toe clearance at control levels, patients were observed to increase hip hiking and hip flexor work, in addition to laterally displacing the surgical toe during swing over the obstacle. Despite allowing individuals to maintain adequate toe clearance, these compensatory strategies may lead to an increased instability and pose a threat to safety in this population. In addition, an increased demand placed on the hip joint of the surgical limb may be undesirable in this population. Research aimed at determining how to best maximize surgical knee function must continue if these potential negative sequela are to be minimized. # 2002 Elsevier Science B.V. All rights reserved. Keywords: Total knee arthroplasty; Locomotion; Obstacle avoidance; Kinetics; Kinematics; Elderly 1. Introduction As the largest and most complex of the lower limb joints, a properly functioning knee joint is integral to humans’ ability to stand and manoeuvre in their environment. In order to function normally, the knee depends on a complex interaction of ligament support, coordinated muscle activation and, to a lesser extent, bony structure for the stability and control needed to support body weight during upright stance [1]. This intricate balance is disrupted when the knee joint is replaced with an artificial joint, as during total knee arthroplasty (TKA). A wealth of research has examined how knee function is affected by this surgery, much of it focusing on range of motion (ROM), strength, kinetics, joint kinematics, wear rates and general surgical out- come. In contrast, the effect of unilateral TKA on bilateral lower limb function has received very little attention. Given the complex interaction that occurs between all lower extremity joints during movement [2], changes in knee joint function have the potential to alter ankle and hip function. Investigations of bilateral lower limb performance are, therefore, needed if the adaptive strategies used by individuals following TKA are to be understood. These adaptations observed following TKA may be beneficial (i.e. lead to improved function) and/or detrimental (i.e. place an individual at increased risk); thus, a true understanding of these strategies cannot be reached unless their potential benefits and/or risks are determined. This study will examine the effects of TKA on bilateral lower limb kinetics and kinematics, in * Corresponding author. Tel.:  /1-519-888-4567x6830; fax:  /1-519- 746-6776 E-mail address: sprentic@healthy.uwaterloo.ca (S.D. Prentice). Gait and Posture 18 (2003) 95  /104 www.elsevier.com/locate/gaitpost 0966-6362/02/$ - see front matter # 2002 Elsevier Science B.V. All rights reserved. PII:S0966-6362(02)00164-9