Have knee pain bending, stairs, sitting for too long, hurts try exercises no luck. sometimes leg will get numb while sitting long what is this?

Varies: There are a umber of possibilities, I would not hesitate to be seen and am exam and appropriate studies can likely determine the cause. The most common cause of anterior knee pain that is worse when sitting with knee flexed or going up the stairs is a disorder of the patella; the most common of which is chondromalacia. There are many good nonsurgical options.