Front Squats are a great exercise. They recruit in a slightly different pattern from back squats, encourage good alignment and have crossover effects both in powerlifting and Olympic lifting. Who wouldn’t want to toss in a cycle of those now and then? In an analysis of the same load being front and back squatted in trained, college-aged strength athletes- it was found back squatting resulted in higher compression forces and greater moments arms- so clearly there is more risk. Shear forces were similar in magnitude and muscle recruitment had a negligible difference. What does this mean? If your back and knees can’t handle back squats- try front squats, the load is distributed differently while still working the muscles. Also, as anyone who front squats heavy knows, torso alignment is much more important and you will develop better thoracic extension through this movement much more quickly than a back squat.