National Physical Therapy Examination (NPTE) Practice Exam

In which range of knee motion would isometric quadriceps contraction be most risky after ACL reconstruction?

1. 0-15 degrees

2. 30-60 degrees

3. 15-30 degrees

4. 60-90 degrees

The correct answer is: 0-15 degrees

After ACL reconstruction, the most risky range for isometric quadriceps contraction is 0-15 degrees. This is due to the fact that in this initial phase of knee motion, the knee is in a position where there is limited joint space, and the forces from the quadriceps can place excessive strain on the newly reconstructed ligament. During the early stages of rehabilitation, particularly in the 0-15 degrees range, the tibia is positioned anteriorly relative to the femur. When the quadriceps contract isometrically in this position, it can create a shearing force that might compromise the stability of the graft and the healing process of the ACL. Additionally, this range is crucial for regaining knee extension, and any excessive force can hinder recovery. As the knee progresses through ranges of motion beyond 15 degrees, such as 30-60 degrees or 60-90 degrees, the risk decreases since the forces exerted by the quadriceps are less likely to negatively impact the graft's integrity. Therefore, in the context of a post-operative rehabilitation plan, avoiding strong isometric contractions in the 0-15 degrees range is crucial for optimal recovery following ACL reconstruction.