Thanks for posting your querry.
There may be multiple reasons for joint pains
and weakness in in the back.
I am mentioning some which seem relavant to your problem:
-vit D3 deficiency
I would strong recommend you to visit an orthopedic surgeon or your physician as they will get certain tests doen for you to daignose your problem. The tests required will be:
-Complete blood count
-serum calcium levels
-Vit D3 estimation
-RA factor and uric acid
Till you visit your doctor you can have multivitamin
tablets and calcium tablets. You must also have green leafy vegetables, eggs, fresh fruits and lilk products.
Hope you feel better.