Pre-surgery physiotherapy is primarily to begin to strengthen the muscles for better outcomes post-surgery and a faster recovery. By putting in the work and priming the muscles and joints prior to surgery, the motor patterns are already engrained, so that post-surgery exercises have a head start. Exercises from physio can also help boost lung and heart function, which also helps with surgical recovery. The pre-surgery exercises can help decrease pain and increase function; in some cases, the recovery can reduce the need for surgery at all.
Physio prior to surgery has been shown to improve long term outcomes and quality of life (both before and after surgery).
Post-surgery physio is done to re-strengthen muscles, improve range of motion and increase function of a joint. Once the problem is surgically fixed, a physiotherapist will work with you to get you back to what you want and need to be doing to return to normal life and/or back to sports and activities.