After 50+ there can be so many reasons for the pain in legs & knees,like:
1] Metabolic disorder,like Diabetes,hypertension etc.
2] Degenerative disease,like arthritis/ a stage of osteoporosis
As you said,that you are obese,then it may be because of over weight.
Therefore,I feel that besides reducing weight/taking care of obesity,you must consult an orthopaedician,so that a complete diagnosis of the problem can be identified.
Once the problem is diagnosed,then only you should opt for any therapy.The treatment in ayurveda,allopathy,unani & homeopathy is available.