Eight weeks, four sessions a week, about fifteen minutes each.

Most of it is hip and ankle work. A knee is a hinge between two joints that both rotate, so when the hip is quiet and the ankle is stiff the knee ends up absorbing what neither of them handled. Training the knee on its own works the part that was never the problem.

Bodyweight only. A step or a low chair and some floor space.

Lowering slowly is most of the programme, and it is the part everyone rushes. Includes a five-minute version for bad weeks and an eight-week tracker.