A.L.
As an HR Manager don't tell them in the interview, you tell them when they make you the offer. If you really feel bad and just feel like you have to tell them in the interview, then you have to sell them on the fact that you are still the best person for the job and that they need you in this position because you can do ........
That being said, do you plan to take more than the disability period which is either 6 or 8 weeks? If so that might be a deal breaker. They may still not mind if you only take the disability period but if you plan to take 12 weeks which you wouldn't qualify for(FMLA) that could be the deal breaker for them.