Maybe the robot-joint could be used as rehab to automatically put progressively more weight on the leg as it heals
This makes me think about a e-bike with a control system/transmission that helps you maintain constant output power for a workout, applying resistance or assistance as needed.
Likewise joints that are repairing need to be utilized just enough so that blood and lymph circulation can bring nutrients and repair materials while carrying away by-products of repair thereby not letting it concentrate through sedentariness.