My doctor taped my knee, ankle and found no response. what does this mean,i have been referred to a neurologist?

Tapping the knee at the right point is expected to trigger an involuntary reflex that contracts a muscle group & expends the knee. If it does not, a breakdown in the nervous connection is implied. This likely brought about the referral to confirm or exclude a problem.

Although you do not describe your symptoms, would assume your doctor is concerned about a nerve dysfunction, or even presence of spasticity. A neurologist could uncover cause, leading to more specific therapeutic approach.