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.

The purpose of this study was to determine minimum toe clearance and lower limb kinematics at initial swing and mid-swing phase during walking over the obstacles in patients with knee osteoarthritis after total knee arthroplasty (TKA). Twenty patients aged 65-85 years with knee OA were included to the study before surgery, three and six months following TKA and twenty age-matched healthy controls were collected the data for comparisons. All participants were asked to perform range of motion test, muscle length test, leg length, leg muscles strength test, joint position sense test, single-leg balance test, Knee Injury Osteoarthritis Outcome Score (KOOS). For gait analysis, participants were assessed while walking crossed the obstacles (2.5, 5, 10 cm) which placed at the center of an 8-m along walking path. The data were analyzed using ANOVA with repeated measure followed by Bonferroni’s multiple comparisons. The results revealed the six-month postoperative patients improved gait speed among the TKA patients. When they crossed over the obstacle (2.5 cm), it showed no significant difference in toe clearance at the initial swing phase. At obstacle heights of 5 and 10 cm, toe clearances of the six-month postoperative patients were lower than those of the controls. At the same time points, they also exhibited decreased hip flexion and knee flexion at the initial swing phase but ankle dorsiflexion was changed in a similar pattern of both groups. These altered gait movement pattern with decreased toe clearance had identified as risk factors for tripping during obstacle-crossing due to the toe trajectory closed to the ground surface. Additionally, the lower limb strength of the six-month postoperative patients was weaker than those controls and they also had slightly decreased in static balance compared with the controls. Although the TKA patients could not return to their normal gait patterns, their treatment proved to be successful in terms of knee arthritis, which delivered relatively high satisfaction because the patients experienced pain relief and functional recovery and required improvement in the quality of life. In order to maintain physical performance after TKA, training program of lower extremity such as strengthening of lower limb muscle or balance training exercise may be an important component of the effective postoperative rehabilitation programs.