Hip Pain
The diagnoses of hip injuries have risen over the past decade. Several hypotheses exist to explain this, but the most accepted hypothesis is the increase in understanding and diagnosis of hip impingements.
The American Academy of Orthopaedic Surgeons describes the following types of hip impingement (FAI).
In FAI, bone spurs develop around the femoral head and/or along the acetabulum (the area in the pelvis where the head of the femur lies). The bone overgrowth causes the hip bones to hit against each other, rather than to move smoothly. Over time, this can result in the tearing of the labrum and breakdown of articular cartilage (osteoarthritis) [also read about differences in hip tendon variation].
Types of Hip Impingement (FAI) 
There are three types of FAI: pincer, cam, and combined impingement.
Pincer: This type of impingement occurs because extra bone extends out over the normal rim of the acetabulum. The labrum can be crushed under the prominent rim of the acetabulum.
Cam: In cam impingement, the femoral head is not round and cannot rotate smoothly inside the acetabulum. A bump forms on the edge of the femoral head that grinds the cartilage inside the acetabulum.
Combined: Combined impingement just means that both the pincer and cam types are present.