Calf pain and swelling, Knee swelling.

Hello, my mother is 60 years old and she has been suffering from calf pain for two weeks now. A calf pain is severe where she cannot even walk properly or rather limp a little. The pain is on right leg. There is also swelling of knee but no pain. The general doctor suggested that is b12 deficient and prescribed injections and vitamin medicines. But after taking b12 injections the problem still persists. Infact the injection showed no result as such. I am just concerned that this shouldn't be something different. And don't know as to which specialist I should consult with. The color of her leg is normal. No warm feeling near the pain area. No clots or veins visible except few bluish vein visible on her thigh since 4-5 years.