Thanks for using health care magic for posting your query.
I have gone through your query in detail.
From what you have stated it appears that you might have had a fracture
or a ligament tear at the knee.Many times patellar fracture appears this way and needs help.
Consider getting your knee x-rayed to identify any hairline fracture.
Do consult an orthopedician who can examine your knee.
Hope I am able to help you,
Wish you good health
Thanks and regards
Dr. Srikanth Reddy