National Physical Therapy Examination (NPTE) Practice Exam

Which factor may contribute to excessive knee flexion in the stance phase for a patient with a transtibial prosthesis?

1. The heel cushion is too soft

2. The socket is too far anterior

3. The keel is too long

4. The socket is too far posterior

The correct answer is: The socket is too far anterior

The socket being positioned too far anterior can lead to excessive knee flexion during the stance phase of gait for a patient with a transtibial prosthesis. When the socket is too far forward, it alters the center of mass and the alignment of the residual limb. This misalignment can result in greater pressure on the anterior aspect of the prosthetic socket during the stance phase, effectively encouraging the knee to flex more than is desirable as the body's weight shifts forward. In a properly aligned prosthesis, the knee should remain stable during the stance phase to allow for effective weight bearing and forward progression. An anteriorly positioned socket reduces stability and can cause the user to feel as though they are tipping forward, prompting them to flex the knee to maintain balance. Understanding the mechanics of a transtibial prosthesis is crucial, as subtle adjustments in the socket position can significantly impact functional outcomes and the overall comfort of the patient.