Considering her age knee pain could be due to 2 reasons either knee arthritis or due degenerative changes in her back causing the radiating pain. Detailed evaluation will be required.
Next Steps
Advise you to please visit the nearby orthopaedic or physiotherapist for more accurate diagnosis. Also they might ask for the knee and back X-ray.
Health Tips
Use ice pack if there is swelling along with pain. Avoid crossed leg sitting and sitting in Indian toilets.