Removing the pain isn't the end of treatment. It's halfway. Rehabilitation restores mobility and basic function to the injured area; functional reconditioning gives you back the strength, control and confidence to return to your sport, your job or daily life without fear of the injury coming back.
People often confuse them, but they are not the same and are not done at the same time. One prepares the ground for the other: without rehabilitation, reconditioning isn't safe, and without reconditioning a relapse is only a matter of time.
It starts right after the injury, surgery or diagnosis. The goal is to recover lost function: reduce inflammation, calm pain, restore range of movement to the joint and make sure the tissue heals properly.
It starts when there is no more pain or limitation, and it is the phase that is almost always skipped. The goal here is not the joint, it's the person: regaining strength, movement control and the ability to tolerate load until the body can handle what you will ask of it.
Most relapses happen precisely in the gap between the two: the patient stops having pain, assumes they are cured and returns to activity with half the strength they had before. Rehabilitation closes that gap.
You don't move on to the next phase by calendar but by criteria. Before increasing load we check the previous one is consolidated, with measurements rather than feelings.