In your age the likelihood problem in your knees is degenerative arthritis. It requires multi approach for the same.
Investigation for how much wear and tear and which part of joint is involved.
Exercises and rest in right proportion. Strengthening exercises for knees is highly recommended.
Take your vitamins and
calcium regularly.
Once joints are strong walk at least 3-4 km/ day to build good joint stamina.
Next Steps
since it is a long term problem you must get yourself checked by orthopedic surgeon for any sudden locking or severe pain episodes.
Health Tips
don't get dependant on only knee caps.Build your muscles. it will help you to loose some weight as well. avoid high fatty and sugary diet.