I’m going to write a really quick overview of my understanding of the young adult hip joint (the joint itself, not the region). Well I’m kind of considered an expert on it for some weird reason and you may find some value in it.I was the founder of the Hip Special Interest Group of the Sports Section of the American Physical Therapy Association.I’ve written a ton of articles/textbook chapters on the subject and am currently involved in several research projects trying to answer more questions regarding the hip, specifically in athletes.
I’m not going to give you a bunch of citations for a few reasons: 1. “Pincer” is when the acetabulum covers too much of the femoral head.This is a blog post which makes it cursory, unreviewed, and illegitimate. I could say whatever the hell I want and find at least one citation to support it – means nothing. None of these statements are controversial and I don’t feel like stringing out the 20 possible citations on each. Providing it means nothing since I could be misrepresenting it all. In isolation, I really don’t care about a pincer since its ability to cause any real damage is limited.When we talk about a cam, it gets more complicated.A “normal” (whatever that means) femoral head is spherical in nature.Round peg (femoral head) and round hole (acetabulum) work really well together.
When there is a cam, you no longer have a spherical head, it is more egg or cam shaped.This offset can be measured via the “alpha angle” on frog-leg radiograph.The term “cam” refers to a mechanical concept of an offset shape used for work. Due to its shape, a cam interfaces one way in one position, but another way in another position.For example, when rock climbing, a climber will put a cam-shaped device with a cable or webbing attached into a crack in the rock.When she pulls on the cable or webbing, the cam turns in the crack.The offset shape causes the cam to exert more force on the walls of the crack as it turns and “spreads”.