Strategies Utilized during a Novel Rotary Task in Total Knee Replacement Subjects

Abstract

The ability to perform activities of daily living involving flexion/extension of the knee along with rotation are crucial for total knee replacement (TKR) patients to regain their independence post-surgery. The proposed research identified compensatory strategies used by TKR subjects during a novel rotary task. The task consisted of two activities, a high to low (H2L) and a low to high (L2H) button task where subjects utilized a crossover technique in order to press buttons located at shoulder and knee height by flexing and extending the knee. Ground reaction forces and kinematics were recorded for eleven TKR subjects and twelve healthy controls. Data were modeled in a musculo-skeletal modeling system to determine knee torque, center of mass displacement, and muscular activity. Each leg was categorized as affected (TKR knee), unaffected (non-TKR limb), or a healthy control. No statistical differences were found in the force transfer for the different groups, although differences in the variation of the loading within subjects were noted. Differences were found between healthy and unaffected knee angles and a strong trend between healthy and affected subject's knee angles in both tasks. L2H had the most variation where a significant difference was present predominantly between unaffected and healthy in the knee flexion, knee torque, and hip extensor muscles. Consistencies during both tasks in knee torque and muscle activation while knee angles varied suggests the kinematics during this type of motion is driven by the cross over. These outcomes suggest that individuals with a TKR may utilize strategies, such as keeping an extended knee and altered muscle activation, to achieve rotary tasks during knee flexion and extension, yet these strategies were not reported consistently from task to task. Early identification of these strategies could improve TKR success and the return to activities of daily living that involve flexion and rotation.