How about some best practices…

Know what the essential job functions of each job are. Generally, the job description should reflect this. But, sometimes, job descriptions, well, you know. So, check with your managers/supervisor to find out what your employees do each day. And make sure the job description accurately reflects this. (And if the tasks your employees are performing are inconsistent with your expectations, consider changing managers/supervisors).
When you provide an employee with notice that she is eligible for FMLA, provide the employee with a list of essential job functions that the employee's physician must consider as part of the fitness-for-duty certification. Otherwise, the physician need not consider them.
Consider the ADA too. The failure to restore an employee to her position at the conclusion of her leave does not violate the FMLA if the employee remains unable to perform an "essential function" of the position. And the FMLA doesn't require an employer to provide a reasonable accommodation to perform an essential job function. But the Americans with Disabilities Act does. And since many FMLA "serious health conditions" also qualifies as ADA disabilities, you need to be thinking about the ADA when someone seeks to return to work from FMLA leave.

See also: Don't make an employee work during leave

Instant Insights /

Make essential job functions part of FMLA approval