Claim denials are a common feature of the disability landscape. The largest disability insurer, Unum Group, says it denies almost 10 percent of the claims it receives. But some health conditions are more likely than others to prompt rejections or the third degree from insurers. Here are some of the top trouble spots:

Musculoskeletal disorders make up 23 percent of new disability claims each year, says the Council for Disability Awareness, an insurance industry trade group. Expect heavy scrutiny if you file for back pain, however, especially if you don t have a clear-cut injury, like multiple fractured vertebrae. Insurers even occasionally do surveillance of claimants to see if they re doing activities that suggest they re healthy like hitting the golf course or taking out the trash. They can t stick a camera in your living room window, says Los Angeles disability attorney Glenn Kantor. But if you re out on the street, they can photograph you like you re Angelina Jolie.

Pregnancy Complications

Maternity-related issues make up about 9 percent of disability claims. But Joel Grossman, a third-party claims reviewer in Coral Gables, Fla., says about a quarter of the contested denials his company sees are pregnancy-related. Conditions that require extensive bed rest after birth like preeclampsia, a high blood pressure condition, or a difficult caesarian section can be particularly dicey.

Carpal Tunnel Syndrome

This wrist condition can make typing extremely painful. Surgery developed over the past decade can help some patients, and although insurers can t force someone to go under the knife, they will sometimes rule that a person who forgoes surgery is ineligible for benefits. Going back on the job postsurgery can cause the disease to flare up again, but experts say raising that issue can prompt even more scrutiny from an insurer.

Mental Health

Diseases like depression can wax and wane in severity. As a result, some mental-health claimants have to be careful about what they say on the therapist s couch since a shrink s notes are fair game for insurers to analyze. Say you had a few good weeks or are much improved, and it could be misinterpreted and lead to a cutoff in benefits, says Erin Moaratty, a project officer at the Patient Advocate Foundation.