PDBR was an attempt by Congress to fix the old disability system that we had in place until 2009 (typically called the Legacy system, or LDES). It allows people who went through LDES to apply to get their results changed. As a result, it's only open to people who discharged between 2001 and 2009.
Since you discharged more recently, you can't go through PDBR. However, you can go to the Army's Board for the Correction of Military Records (BCMR). I'm assuming that your results are finalized and you've actually been discharged at this point.
If that's the case, the BCMR is the place to go. Their website is here: http://arba.army.pentagon.mil/abcmr-overview.html. There's a bare-bones description of the process there, so I'd definitely recommend digging around this site for a while to get a better sense of what to expect. Lots of folks have posed about their BCMR experience.
The BCMR is empowered to fix "errors or injustice" in military records, so you'll need to show them why your results were legally incorrect (the easier way) or unjust (the harder way).
When it comes time to file, you will not have access to the Army JAG or PEBLO who helped you with your Med Board. You can apply to BCMR on your own, but I don't normally recommend it because it's an easy process to screw up, it takes forever to get results back, and you only get this one shot at it. Your other options are to contact a VSO like the American Legion or the VFW, who will often help you file for free, or to hire a civilian attorney to assist.
Appreciate I was reserved and former active duty they made both my knees fit when it was unfit at first and they messed up the diagnosis and more inconsistencies about other info my lumbar arthritis was 20% and both my knees are 10%