2005 OITE Question 28

Question

Which of the following rehabilitation exercises places the most stress on the anterior cruciate ligament?

1- Resisted non-weight-bearing knee extension between 0 and 30º

2- Vertical squat to 60º

3- Leg press

4- Stair climbing machine

5- Stationary bike with high seat placement

Figures

Answer (click for answer)

PREFERRED RESPONSE: 1

Different forces are transmitted across the knee joint during open versus closed kinetic chain exercise. Closed kinetic chain exercises occur with the foot fixed. Knee motion therefore occurs as a result of coordinated ankle and hip motion. During this type of exercise, anterior tibial shear force, and thus ACL stress, is significantly less than during open kinetic chain exercises. In contrast, closed kinetic chain exercises result in compression across the knee and maximal posterior shear. In vivo and cadaveric studies have confirmed anterior tibial shear during open kinetic chain exercises and demonstrated the last 30 to 40° of knee extension to result in the greatest ACL strain.

Of the five answer choices, only resisted non-weight-bearing knee extension between 0 and 30º represents an open kinetic chain exercise. Moreover, the range of motion described is associated with the highest anterior tibial shear and ACL stress of the entire range of motion. Vertical squat to 60º (half squat), leg press, stair climbing machine and stationary cycling are all forms of closed kinetic chain exercises, which are recommended for exercise and rehabilitation for the ACL-reconstructed knee.

Reference: RECOMMENDED READINGS: Wilk KE, Escamilla RF, Fleisig GS, et al: A comparison of tibiofemoral joint forces and electromyographic activity during open and closed kinetic chain exercises. Am J Sports Med 1996;24:518-527.


Beynnon BD, Johnson RJ, Fleming BC: The science of anterior cruciate ligament rehabilitation. Clin Orthop 2002;402:9-20.