As per the history,he is already diagnosed with RA.Its an
autoimmune disease in which the joints cartilages are destroyed by immune system .it usually progresses over time.with medicines it can be controlled or slowed down like pain ,movements upto an extent it is.but it takes time.Hope his knee joint x-ray are taken if not,you need to do it.In RA the
stiffness is the main problem after that the pain so for this
physiotherapy might help.Exercising regularly and keeping yourself active helps.Not much but slight exercise is good.In this disease there is destruction of the joints occur,it can not be stopped but slowed with medicines.He is also diabetic so need to keep the sugar level in control.If he is
overweight then its good to get a diet chart prepared and follow it and bring the weight under control so that knees wont get pressurised much as they are already in pain.treatment included DMARDs,
corticosteroids,painkillers mainly.it takes time to show the effect of medicine but it provides relief.If these are not doing good then next option is biologicals,these are given i.v in a regular interval.You can talk to your doctor about it.If he or she thinks it can be given to him now then its a good option.Intra articular injections are also given as the lubricant fluid is reduced in the joints .so if needed that is also given just consult your doctor with recent x-rays. Do not miss the medication in between.Also do cbc,
ESR,LFT,KFT every 2-3 months and get it checked by your doctor.I hope his CRP,ANA,RA factor,Anti CCP,vit D levels,knee joints,shoulder joints,hand x-rays are done and seen by the doctors.If anything is not done kindly do that and show it to your doctor.stay positive,the disease can be brought under control and you can do the daily activities fine.