HI,
For knee instability, we should find the courses of this, congenital or acquired. If it is congenital, we should know what the problem is: such as joint disfiguration, muscle unbalance and so on. If it is acquired, we should find what is the courses such as injury and it is acute or chronic.The patient should be given some exercises, quards strengthening ex, after RICE technique, Rest, Ice, Compression and Elevation, Be careful in tendon injuries, muscle injuries, not to forget to do RICE.
Yours sincerely, THIRI(Physiotherapist)