In most states, when a worker who has filed for workers' comp benefits is able to return to light duty, the employer must return the worker to the job he or she left or an equivalent job, provided that such a position is available.
However, in some states, going back to work in a light duty capacity may mean that an employee still needs to be paid workers' compensation benefits to make up the difference for what he or she would have earned in their regular position were they fully recovered. Sadly, for this reason, some employers will claim they have no light duty employment available, simply to be able to stop paying workers' compensation benefits.
In other states, the law has changed recently to encourage employers to offer modified or alternative work. Whether or not you accept an offer of light duty, or alternative or modified work, can affect your permanent disability benefits. In California, for example, if your employers offers you modified or alterative work, your permanent disability benefits will decrease by 15% (meaning the employer's insurance company has to pay you less) -- regardless of whether you accept or reject the offer. The modified or alternative work must be work that you can do. If the employer doesn't offer you modified or alternative work, your permanent disability benefits will increase by 15% (meaning your employer's insurance company will have to pay you more).
If you do return to your previous employer, make sure your employer knows about the restrictions your doctor has put on you, such as no lifting over 20 pounds. If your employer asks you do do some heavy lifting anyway, decline the task and say your doctor has recommended against it, and document the occurrence. If your employer has provided you with light duty or modified work, the employer can't fire you for not doing work that your doctor says you shouldn't do.