First Of  all take properly medicine  than start  gradually Q drill, than u get think  Knee replacement.

Age is OK. Tk calcium supplement and quadriceps exercises in gradually process and physiotherapy treatment Start this before replacement if it work then OK otherwise surgery

Quadriceps strengthening exercises- Quad Clenches: Lie flat on your back or sit upright on a chair with leg kept horizontally on another surface. Now, tighten the muscle on the front of the thigh by pushing your knee down. You should feel your thigh muscles clench, Hold for 3 secs. Repeat 10 times twice a day. Short Arcs: Lie flat on your back or sit upright with your leg placed horizontally on a flat surface like a chair or bed. Place a rolled up towel under the knee. Pull your toes towards you and clench you thigh muscles. Slowly lift your foot up off the bed until your knee is straight (keep your knee resting on the towel). Hold for 3 secs and slowly lower them on the chair. Repeat 10 times twice a day. Straight Leg Raise: Lie flat on your back. One leg and knee will be straight and other leg should be bent. Pull your toes towards you and tighten/clench the muscle on the front of the thigh, locking your knee straight. Lift your foot up in the air, about 6 inches off the bed. Hold for 3 secs and slowly lower the leg. The knee must remain straight the whole time you are doing this exercise. Hamstring stretching Towel Hamstring Stretch Lie on the back, supporting the thigh with the hand or with a towel wrapped around it.. Slowly straighten the knee until a stretch is felt in the back of the thigh, trying to get the bottom of the foot to face the ceiling, one leg at a time. Hold the position initially for 10 seconds, and gradually work up to 20 to 30 seconds. Seated Hamstring Stretch While sitting at the edge of a chair, straighten one leg in front of the body with the heel on the floor. Then, sit up straight and try pushing the navel towards the thigh without leaning the trunk of the body forwards. Hold this stretch for 30 seconds Repeat 3 times for each leg.

I will have to see the X-ray in order to comment on the knee replacement. Also, it is important to clinically assess the patients knee and know how much pain he is suffering from. According to me, he can extend the knee replacement surgery by 5years if he takes good physiotherapy treatment regularly. Swimming is the BEST exercise for him. Regular soft tissue work and mobility exercises will also help him reduce stiffness and increase mobility. Kind Regards, Dr. Kshama Dhawan, Shah Polyclinic

Hello sir , pain in knees may be due to over exertion of knees.u shd get x ray check if the problem is at moderate level then u see a good physio he may help u And for osteoporosis u may see a good ortho In the meantime u do hot fomentation plus knee exercises thanku