I am a dancer and at random moments my knee bothers me why is that?

Probably overuse: Although impossible to say for sure withou t an evaluation, overuse injuries (arthritis, chondromalacia, tendonitis, bursitis, etc) are common in dancers.

Sudden knee pain: Pain with random movements of the knee is going to probably be related to what you were specifically doing at the time. If you were jumping, squatting or twisting it could help with the diagnosis. Also if there are mechanical symptoms: locking , catching, popping, clicking or giving out ; will also help diagnosing your problem. I find dancers often have patella tendonitis.

Footsies check up !: Have a podiatrist examine your feet. As an avid dancer of mostly latin music, i can tell you that inserts/ support has kept me dancing into my early 50's without feeling like couples around me are kicking me in the heels, calves, knees and gluteus major. Both of them.

Consider: An evaluation by an osteopathic physician. Dos are trained with a holistic approach. There may be knee pathology, but there may be issues with conditioning or weak or misfiring sequence of muscles. A do may be able to perform manipulative technique to better evaluate and treat ur condition. If appropriate, injections, meds, imaging, therapy or referral may be employed.