
One legged squat, left leg is weight-bearing. Posture should be as straight-backed as possible with head up looking forward. I have a tendency to lean forward from the hips as I get fatigued which is evident here in a slightly rounded back
When I first began rehab I was told that the one legged squat is the most useful exercise for recovery. That has certainly been the case and I have done a lot of one legged squats in all sorts of different formats. An easily achievable one is shown below. I can do three sets of squats where each set consists of 10 to 12 repetitions.

Right leg weight bearing. The one legged squat second movement. This not only strengthens the weight bearing leg but also stretches the hip flexor tendons in the non-weight bearing leg

The one legged squat at the starting position with one leg raised behind and all the weight bearing on one leg. Note the square shouldered upright position. Left leg here is weight bearing
It is important to try and touch the nonweight bearing knee almost to the floor in the squat before driving straight up with the weight bearing leg. Back must stay straight.