Pain behind right knee

Hi, playing basketball, went up for a right corner jump shot, and felt a sharp pain in the back of and to the outside of my knee. I got movement back after a few minutes. Iced back of knee right away. Had some swelling the following afternoon, but to the inside of my knee. Very little swelling to the back of it. Had no bruising of any kind. But had a numbing feeling from my calf down to my achilles an hour or so after the injury occurred for the rest of the nite. Went to a specialist, and said it was a knee sprain. Gave me excersises and anti-imflammatory medicine. Well 5 weeks later, and still can only bend my knee in half way without pain. Knee also feels wobblely. Cannot play any kind of sports yet. Looked on this website and found it possibly could be a hamstring tendon problem? If anybody has any ideas about what it could be, and any excercises for it. Would greatly appreciate it!!