Polo wraps actually don't provide any support for your horses legs. I personally use the SMB Elites. They are expensive, but my gelding bowed a tendon last year and my vet told me he could only be worked if he was wearing support boots, so I bought them. They're very easy to apply, almost foolproof, and provide great support. They also fit very well and come in tons of cute colors. They are an investment, but they have a one year warrenty and mine are used on a regular basis and still look and feel new.
I've spent most of my life riding horses. The rest I've just wasted.