Treadmill is definitely not the right choice if your mother is having knee pain but you can consult Ayurvedic physician who also has diploma in diet and nutrition so that your mother can loose weight along with treatment for knee pain. Some ayurvedic medicines work  in both these conditions.

Your mother need more than 45 KGS wieght loss. What is her age. Any electronic device will create more problems as they create current which put more pressure and increase knee pain .knee pain is also due to heavy weight.I can help youwith 4-5 KGS weight loss in month through purely diet na d exercise. It should be in natural way to make it permanent.

Hello,  as your mother has knee pain it's not advisable to use any exercise machine which strain on knee.  So electronic treadmill won't be helpful for her.