Seth Hosmer
Nobody can give you an estimation of how quickly you can get back to riding until you've had an evaluation of the knee. The examination would assess ligament stability, along with other ortho tests to give some indication regarding what was damaged in your accident.
If the knee is stable and there is no evidence of other things being torn, you can probably get back to activity relatively quickly. OTOH, if the exam suggests that something is torn or damaged, you may need a follow up MRI to get a better sense of the tissues that are damaged, and how badly they are damaged. From there, rehab would help make sure that your return to activity is a successful one.
This is something that I can help you with.
Seth Hosmer, DC, CSCS
www.HPChiro.com
503.227.2279