Obstacle Crossing in Older Adults with Total Knee Arthroplasty at the Initial Swing Phase

After undergoing a total knee arthroplasty (TKA) procedure, patients are at a high risk of falling because they present with ineffective mobility within a complex environment, especially during obstacle crossing. Toe clearance (TC) is an important factor to quantify the risks of trip-related falls. The study aimed to investigate TC height and toe trajectory and joint kinematic changes occurring in the lower limb following TKA during obstacle crossing at the initial swing phase. Twenty TKA patients, including those in preoperative and postoperative stages (three and six months), performed obstacle-crossing tasks to compare their performance with 20 healthy controls. Participants walked at self-pace along an 8 m walkway with 2.5, 5, and 10 cm obstacles positioned along the center of the path. For each participant, body segment motions were traced using reflective markers and the kinematics of lower extremity, toe clearance, and gait parameters were analyzed using a 3D-motion analysis system. TKA patients had lower TC height and toe trajectory at six months, slower toe elevation than controls when swing toe crossed 5 and 10 cm obstacles (p < 0.05), and decreased hip and knee flexion (p < 0.05). These altered gait patterns with decreased TC height and toe trajectory were identified as tripping factors as the toe trajectory was close to the ground surface. TKA patients had acquired different lower limb kinematics to maintain adequate TC. At long-term follow-up, there was an increasing trend for patients to trip after surgery. Therefore, more focus is needed on the exercise prescription for rehabilitation programs to improve muscle strength and stepping control.