Thank you for posting your query.
There are two likely causes for your mother's symptoms:
of hip joints- it is common in older people. X-ray of the hips can help in diagnosing this condition.
2. Lumbar disc disease
with compression of the nerves at back- this can lead to pain and weakness of legs.
An additional condition to exclude is osteoporosis- weakness of bones- which is again common in old age.
An evaluation by a neurologist/orthopedician could be useful in sorting the problem out and planning the treatment.
Dr Sudhir Kumar MD DM (Neurology)
Senior Consultant Neurologist