My new knee was five weeks old yesterday, and at physio I was doing a flex exercise, pulled a tendon in the back of my knee. Excruciating pain, now I can't bend the knee at all. I was doing SO well, making great progress, don't know how long this will take to heal. Has anyone ever had this happen? It feels as if I disconnected something that runs up from my calf to my thigh through the back of the knee. Phooey!!