Thank you for your question. We’ll do our best to answer it well, but please keep in mind that we are unable to make a specific comment on your condition without a physical exam.
It sounds like you have tried several wise approaches to addressing your knee pain. Ice, rest, and stretching are all good places to start. Based on the location of your symptoms and provoking factors, you may truly have patellar tendonitis, or you may have something like sprained knee or ligamentous instability elsewhere that is causing increased irritation to the outside of the knee. Patellar tendonitis would most commonly feel painful right over the tendon and be painful with squatting and stairs, while an injury to your ligament would feel like your knee sometimes was unstable or “giving out”. Another possible reason for your knee pain could be abnormal body mechanics at your hip or low back that are putting extra stress on your knee in the positions you mentioned.
Whatever the source, this would likely benefit from further in-person investigation if it is provoked at all by motions you do in basketball (i.e. cutting and pivoting). A physical therapist would be able to assess the tissue around the knee in order to give you a diagnosis, treatment options, and a movement analysis to prevent this and other injuries from occurring. This is best done before the season so that you don’t end up with an injury that grows during the season and eventually keeps you out of play.
Please note, this reply is for informational purposes only. It’s not intended to be a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of your physician, physical therapist, or other qualified health provider with a medical condition.