The first medical step to overcome in proving your Social Security disability case is to show that your medical condition is severe AND that it will either end in your death or last at least 12 months. This duration requirement is important because in many cases the condition is severe but will not meet the duration requirement.
The duration requirement is why a pregnant woman on bedrest for most of her pregnancy is not eligible for Social Security Disability. The duration requirement also causes some cancer cases to be denied initially as recovery is expected within the 12 month period. Other conditions that could be resolved with surgery may be denied due to the duration requirement.
This does not mean that disability cannot be proved, but rather that time may end up being a supporting factor in your case. The 12 month duration has passed and your condition remains. But without meeting both severity and duration, Social Security cannot move on to determine if your condition is disabling or not.