Thanks for posting,
One can not tell for sure how long it will take the pain and knee rigidity to completely heal but with good and proper treatment the injury
can be healed. My suggestion is that you get an MRI
or X-ray of that knee. The tendon might be ruptured after the sprain
or twisting. If after the scan we are sure that there is no major injury besides the sprain, then physical therapy
needs to be added to your current treatment (i suppose they are pain killers/analgesia/NSAID
included). If any serious injury then the orthopedic surgeon will indicate the rightful treatment.
Hope this helps