Final answer:
D. Simultaneous quadriceps and hamstrings contraction at 60 degrees is likely to cause the most strain on a reconstructed ACL, due to the opposing forces exerted by the two muscles creating a push-pull effect on the knee.
Step-by-step explanation:
The question centers on identifying which of the following rehabilitation activities will cause the MOST strain to an ACL following allographic reconstruction. The anterior cruciate ligament (ACL) is crucial for the stability of the knee, and during rehabilitation, specific movements can place differing levels of strain on it.
Answer A and B involve isometric contractions of the quadriceps, which imply holding the muscle in a fixed position under tension. Isometric contractions at 60 degrees (A) generally place less stress on the ACL than at lower angles like 15 degrees (B), due to the mechanics of the knee joint and the position of the ligament within it. However, even more strain can be caused when both the quadriceps and hamstrings contract simultaneously, as they create opposing forces on the knee. Therefore, for option D, the simultaneous quadriceps and hamstrings contraction at 60 degrees, this action could stress the reconstructed ACL more due to the push and pull effect on the tibia.
Option C, an isometric hamstring contraction at 15 degrees, is unlikely to cause the most strain to the ACL since hamstring activity generally provides support to the ACL by pulling the tibia back and counteracting the forward force exerted by the quadriceps.