Hi knee pain is common with oldage people not walking or not  doing regular exercises.Most important is the weight if they increase the weight  and when  person stand it will for 4times on knee joint.And also with improper nutritional . 

So people who is suffering from knee has to consult with Ortho and get necessary investigation,if it is OA(Osteoarthritis) the person has to do regular Exercises by consulting Physiotherapist.

Simple Exercise where patient can do in there home

-Regular walking with sport shoe

-Knee and Ankle stretching exercise

-Knee tightening exercise with help of blanket or small pillow under the knee

-weight of 1 or 2 kg with leg raise