When you applied for the policy, did you answer all of the questions honestly? If you were asked about prior injuries/illnesses/surgeries, etc. and failed to disclose the full information, this is considered material misrepresentation. Not only can the company deny the claim for pre-existing conditions, they can rescind the policy, give you all your premiums back and cancel the policy.
If you answsered all the questions honestly and the underwriting dept. chose to issue the policy after knowing all the history, then you're safe, unless there's a specific exclusion. For those exclusions, you'll need to ask your agent or better yet, read your policy.
Former life and health underwriter and current owner of an insurance agency. Over 21 years experience.