I am 22 years old and within the last 3 weeks I would say, I have been experiencing constant knee pain. It is worse when I bend it and sit for a while then straighten it out and walking up or down staris makes it worse too. Bad knees run in our family…dad has had 6 knew surgeries and 16 year old brother just had his first 8 months ago. I have done physical therapy for my knee before, when I played basketball, but then I quit basketball and haven’t done therapy in about 8 years. When should I see the doctor about it?