What muscle group would you strengthen to provide dynamic stability for the loss of stability from a torn anterior cruciate ligament (ACL)?

a. Quadriceps muscles
b. Adductor muscles
c. Hamstring muscles
d. Gluteal muscles

ANS: C
The ACL limits anterior translation of the tibia on the femur. If this ligament is compromised, another force will need to help provide the same function. As a dynamic stabilizer, the hamstring would be best suited for this purpose. As the hamstrings contract, they provide a slight posterior translation of the tibia.