Thanks for the additional information.
You raise a very interesting possibility, and it may well be that you are actually being discriminated against. However, if the doctor who is sandbagging you is not an employee of your employer---it may be a bit more difficult to prove discrimination on your employer. you would have to show some sort of connection---such as a nod and handshake between the employer and the doctor---almost a conspiracy---to eliminate the older workers through a scheme like this.
It can't hurt to report your suspicions by filing a complaint with the EEOC (Equal Employment Opportunity Commission).
If your company has 15 or more employees, they are prohibited from discriminating against you. To file a complaint with the EEOC, contact the nearest Equal Employment Opportunity Commission field office. To be automatically connected with the nearest office, call(NNN) NNN-NNNN EEOC website: www.eeoc.gov
After you file the complaint, your employer will be prohibited from any retaliatory action against you. The EEOC will investigate your claim, and 180 days after the filing of the complaint you may ask for a "right to sue letter". The EEOC will issue you the letter which gives you the right to institute a private civil action against your employer and seek monetary damages.
I do still think that perhaps a local Workers' Compensation attorney may well be your best chance of nipping this in the bud though---and you can do this at the same time that the EEOC complaint is moving forward.
I wish you well.
I hope that you found my answer informative, that you are accepting of my efforts and that you will rate my efforts based on the knowledge I have provided to you.
I wish you the best in 2012.