I had a tillaux fracture in my ankle. because it wasn't too bad i got a full leg cast instead go surgery. i am having trouble bending my knee and my leg is thinner. is there anything i can do to help my knee while i am in a smaller cast below the knee?

Yes: If you have been transitioned from a long leg to a short leg cast because the fracture is healing, but you are dealing with the atrophy as a result, you could begin exercises for the leg. This can include straight leg raises, leg extensions, and leg curls. You would not want to do any activity that places stress across the fracture.

Age?: this makes no sense You are 20 and stop growing by 16 unless there is some endocrine disease. Till aid fractures only occur in teenagers who still have a partially open growth plate At your age that is impossible. Thus the term tillage fracture is wrong. I don't know what kind of fracture it is so the question cannot be really answered without more information