It is a long time since your fracture. It is unlikely that you can gain back full range of motion after such a long time, without any intervention. Physical therapy may help a bit, but may not alter it significantly. Surgical treatment is recommended, only if the loss in motion, significantly affects your activities of daily living. In that case, arthrofibrosis (or breakage of adhesions) can be tried through arthroscope. But it may not be enough, since it has been a long time, and there may have been significant fibrosis. A surgical procedure like quadriceplasty may be required, but may not be justified if there is no sufficient morbidity or limitation in routine activities.