There are various types of knee fractures
. If it involves the hinge joint of your knee, recovery to full normal movements is less likely. However, if otherwise chances of near normal recovery would be high if you had performed exercises earlier after your treatment.
Now the question is what is preventing further movements of your knee. It could be a shortening/tightness of your muscles and/or ligaments or an irregularity of bone within the joint.
You need to visit your Orthopaedician and get an Xray done. The need for surgery and type of surgery would be decided after that.