“I had an ankle ligament tear a year back which has still not healed completely. What could be the reason?”

Ligaments are not contractile tissues like muscle. As you may know, ligaments connect bone to bone. They are like rubber bands in that if you over stretch them they won’t return to normal length. A tear, if significant enough, would result is surgery to repair it. I would suggest as assessment with a physical therapist to look at your mechanics (how you move) and strength that could be impacting the strain on your ankle. Muscles move bones so your body’s muscles can kind of serve as a second line of defense.

Hi
That’s a long time for healing to happen. You might need to see a PT for the same that way it will help it heal completely.
Regards
Ramky

A full year for a ligament injury to be fully healed is more than it should be. You need to see an orthopedic doctor for a 2nd opinion. In the meantime, you should have your ankle casted below the knee, rest it, and avoid weight as much as you can.

There are many possible reasons you are still having pain and there is not one specific exercise that you should perform over others. Generally speaking, a blend of joint mobilizations, varied strengthening exercises and pain modalities are your best option. Get/continue with physical therapy for the best results.