Check out www.socialsecurity.gov
From the Social Security Website:
"The definition of disability under Social Security is different than other programs. Social Security pays only for total disability. No benefits are payable for partial disability or for short-term disability.
Disability under Social Security is based on your inability to work. We consider you disabled under Social Security rules if you cannot do work that you did before and we decide that you cannot adjust to other work because of your medical condition(s). Your disability must also last or be expected to last for at least one year or to result in death.
This is a strict definition of disability. Social Security program rules assume that working families have access to other resources to provide support during periods of short-term disabilities, including workers' compensation, insurance, savings and investments."
For short term / long term disability insurance I would check into employer offered benefits which if you have you'd probably be paying for at least the short term disability premiums from your work checks. Maybe these are available to individuals also, sorry I don't know about that part...