This is similar to a traditional squat, except you will only be using one leg. Start in a standing position with your feet about shoulder width apart then lift one leg off the ground. Form should be as close as possible to the traditional squat with toes pointed straight ahead or turned out somewhat. Begin by bending the knee of your standing leg and lowering your hips towards the ground. Move your hips back as far as possible during the descent, instead of your knees moving forward. Your knees will move forward some, but if your hips are over your ankles, it puts unwanted stress on your knees.
It’s important to keep your hip, knee, ankle, and toe of the working leg aligned as much as possible. You should ideally be able to draw a straight line between these joints. Finally, the movement should be slow and controlled (no bouncing at the bottom) and your heel should stay on the ground throughout the squat. These technique tips are the difference between an effective lower body strengthening exercise and a knee damaging exercise.
Performing a squat on one leg is naturally more difficult from a strength standpoint, since one leg has to support as much weight as both legs do in a regular squat. Additionally, this exercise puts a greater stabilization demand on the lower body muscles and joints. To maximize the benefit, focus on keeping your hips as level as possible. In other words, if you draw a line between your hips, it should be as horizontal as possible throughout the exercise.
Perform up to 15 reps on each leg and breathe out while you are standing up. If the stabilization is too challenging or your range of motion is too small, you can hold on to something with one hand to provide extra support.