Which ever is the cause now your mother developed generalized Artheritis of lower limbs resulting massive stiffness
and restricted movement and deformities at the joints.
You go for blood check up for uric acid,S. cholesterol
,blood sugar,R.A. test etc.
Now only treatment is analgesic
medicine and PHYSIOTHERAPY
It requires long course of physiotherapy for muscle stiffness and immobility
Consult Orthopedic surgeon for differential diagnosis.
Ok and bye..