It's possible that you have a nerve trapped. You may have injured yourself somehow, which may be why you tore those ligaments and got a nerve trapped in the process.
As far as brain lesions go, MS is NOT the only thing that causes them. They can be caused by migraine headaches, hypertension, diabetes, infectious diseases, nurtitional deficiencies, collagen vascular disease (ie, lupus) injuries, or just as a normal part of aging. They are pretty common in the general asymptomatic population
It sounds like you need to see a different doctor, perhaps an orthopedic physician?