What causes a knee not to straighten? i have been to a orthopedic doctor and he doesn't seem to know. i have had pelican removed

Let me explain: Having the plica removed should not cause this problem. There two mean reasons for the knee not to straighten completely. 1-mechnical, were an object get in between the to prevent it from doing so(locked knee). 2-contrature of the muscles or capsule of the joint which prevent it from doing so. Seek a second opinion to know what is the problem.