Is topamax (topiramate) a good choice to treat terrible knee pain?

No: Topamax (topiramate) is an antiseizure medicine which has been used for management of various neuropathic or nerve related pain disorders. It is also used in management of migraine. Typical knee pain is more of a mechanical pain which may not respond adequately to anti-neuropathic pain medications. If, however, the knee pain is as a result of nerve injury then topamax might a be valid choice.

Probably not: Topamax (topiramate) works best for "neuropathic" or nerve damage pain. Severe knee pain is most likely due to osteoarthritis of the knee which would not be expected to respond to topamax (topiramate). An accurate diagnosis of why there is knee pain is needed first. I would recommend seeing your primary care physician or an orthopedic surgeon.