Once your new joint has completely healed, you will reap the benefits of the surgery.
These include:
Reduced joint pain dramatically (may be no pain)
Increased movement and mobility
Correction of deformity
Improved quality of life – the ability to return to normal activities
Running, jumping, jogging or other high impact activities arediscouraged. However, you can resume playing golf, walking, bicycling, swimming and other low impact sports

Although knee joint replacement is recommended in older age group, it can be considered in younger patients who are severely crippled due torheumatoid arthritis or post traumatic osteoarthritis of knees. As such, age is no bar to this operation.

Yes you can, but your unstable joints may cause a fall and you may have fractures around the knees and the hips because of osteoporotic bones.
Regular consumption of analgesics and anti-inflammatory drugs may damage your kidneys and cause ulcers in your stomach.

TotalKneeReplacementsurgeryisanelectiveprocedureYourdoctorhasmorethan likely treated your condition with physiotherapy, pain medicines, anti-inflammatory drugs and injections in the knee You may have also had minor surgeries of your joint in the past.

You would be considered for total knee replacement if:
you have daily pain
your pain is severe enough to restrict not only work and recreationsbut also the ordinary activities of daily living
you have significant stiffness of your knee you have significant instability (constant giving way) of your knee
you have significant deformity (knock knees or bow legs) causingpain and inability to walk
You and your doctor are probably the best judge of when you will finally need total knee replacement surgery.