The current theory of FAI and pain is that the malformed bones lead to degenerative changes in the hip joint which results in pain and discomfort.
There are some major problems with this theory.
First, FAI has not been shown to lead to arthritis.
Second, arthritis in an X-ray or MRI has not been shown to be related to pain!
1) FAI hasn't been shown to cause arthritis.
Doctors and surgeons often state that FAI bone shapes will lead to arthritis rather quickly.
There is actually NO evidence to support this belief.
It's belief that a few well-intentioned surgeons started, but subsequent studies have shown that it's not true.
As one surgeon puts it...
"I regularly hear from patients that they are going to develop arthritis of their hip if they don’t have surgery to correct their FAI. Although some information exists on osteoarthritis secondary to grossly visible deformities (severely abnormal ball or socket shapes), there is almost no information on the natural course of more subtle femoral or acetabular deformities as present in FAI."
In fact, when you dig into the research, studies show that there is weak to NO relationship between FAI and arthritis.