I fractured my index finger while playing cricket, fracture was just above the knuckle(when we count fingertip being the top). Now the fracture has recovered. I did physiotherapy for the same and  religiously performed the recommended exercise over and over again for more than 4 months. Eventually, pain in the fractured point have subdued, however, there is no movement in the "middle joint" of the finger on its own. Also, its not stiff , I can bent my finger using external force to at least 70°. What should be the reason for this problem? Please comment on this issue.