Although the leg extension is frequently recommended as a “safer” alternative to the squat, new research shows that the squat places no more stress on ligaments in the knee than the leg extension.

One of the reasons for the low stress on knee ligaments during the squat is the fact that your hamstrings (the muscles in the back of your thigh) work at the same time as the quadriceps (the muscles in the front of the thigh).

If you do have a knee injury, it’s best to seek advice from a qualified sports injury specialist. However, if you have healthy knees, there’s no reason to avoid the squat - it’s one of the most effective exercises for building strength and size in your legs!

Reference
Beynnon, B.D., Johnson, R.J., Fleming, B.C., Stankewich, C.J., Renstrom, P.A., & Nichols, C.E. (1997). The strain behavior of the anterior cruciate ligament during squatting and active flexion-extension. A comparison of an open and a closed kinetic chain exercise. American Journal of Sports Medicine, 25, 823-829