Tibial displacement and rotation during seated knee extension and wall squatting: a comparative study of tibiofemoral kinematics between chronic unilateral anterior cruciate ligament deficient and healthy knees. (2013)

From the study:

“Following anterior cruciate ligament (ACL) rupture, the knee becomes unstable with alterations in joint kinematics including anterior tibial displacement (ATD), and internal tibial rotation. Therapeutic exercises that promote faulty kinematics should be discouraged, especially early post-reconstruction, to avoid graft stretching and possibly longer-term osteoarthritis. Our study aimed to compare ATD and tibial rotation during two commonly prescribed exercises, namely: open kinetic chain (OKC) seated extension and closed kinetic chain (CKC) single leg wall squatting in ACL-deficient and healthy knees.”

“We found increased ATD in the wall squat compared to the seated extension (p=0.049). There was no difference in ATD between the healthy and ACL-deficient knees but overall the tibia was significantly more internally rotated (p=0.003) in ACL-deficient knees, irrespective of the exercise, possibly interfering with the screw-home mechanism.”

“CKC exercises, in particular wall squats, are not necessarily safer for patients with ACL-deficiency and possibly ACL-reconstruction; although generalization should only be made with appropriate caution. Clinicians require a detailed knowledge of the effect of exercise on knee joint kinematics.”

Chad’s comments:

I’ve never been a fan of wall squats. What I like about regular squats compared to exercise machines is that you train balance and coordination at the same time you train for strength. By leaning back against a wall when doing squats you take that balance aspect away and you might as well just be doing leg presses. The problem with wall squats as compared to leg presses, however, is that you are stuck with body weight as resistance, but with a leg press I can make the exercise considerably lighter, making it much easier for patients to get started strengthening after injury or surgery. So wall squats have always been the worst of both worlds. Now to top it off these researchers find they put potentially harmful stress on the post surgical ACL.

One potential concern in the above study is that the wall squats were performed with body weight, while the leg extensions used only 3 kg. The different intensity of quadriceps contraction might be a confounding variable; however, that goes back to the weakness of the wall squat as an exercise: you can’t easily and consistently grade and progress the exercise early after rehabilitation. Plus, later on when the ACL graft is strong there are a lot better and more dynamic body weight and body weight plus exercises to choose from than the wall squat. Like regular squats, lunges and RDLs.