National Physical Therapy Examination (NPTE) Practice Exam

The failure to achieve which motion can lead to extension lag post-surgery?

1. Active knee flexion

2. Passive knee flexion

3. Passive knee extension

4. Active knee extension

The correct answer is: Passive knee extension

The failure to achieve passive knee extension is significant because, after certain surgeries such as those involving the knee joint (like ACL reconstruction or total knee arthroplasty), maintaining full extension is crucial for functional mobility and the recovery process. When the knee cannot achieve passive extension, it indicates that there is a restriction in the soft tissues or the joint itself that prevents it from reaching the full extended position. This can result in an extension lag, which means that the patient cannot fully extend the knee when attempting to do so actively, despite having the passive ability to move it into extension. In contrast, achieving active knee flexion, passive knee flexion, or active knee extension may not directly lead to an extension lag. These movements are important for rehabilitation, but they do not specifically address the importance of passive extension for preventing extension lag. Therefore, inadequate passive knee extension post-surgery can specifically result in functional limitations and difficulties during activities such as walking, squatting, or climbing stairs, making it essential for therapists to focus on regaining this motion during the rehabilitation process.