), then obviously you need to see a doc about perhaps a brace
or whatever it would take to help support that weak knee
. A sports injury doc might be your best bet, they are so very good at diagnosing your sort of problem, they are always closely associated with physical therapy people, and they could order a brace, just everything you need. Or your own regular physicians could easily determine what is going on, a scan might reveal a joint problem, or just a regular exam of you.