Hip Impingement: Overview

Hip Impingement: Overview

Hip impingement is a common condition of the hip that can arise from several different causes. Healthcare providers will specifically refer to it as femoroacetabular impingement, or F A I for short. It is named after the 2 bones that are involved.

Hip impingement is when these 2 bones end up contacting each other or impinging on each other with certain hip movements. This causes pain in the front of the hip, often leading to injury or tearing of cartilage in the joint.

To understand how this problem occurs, let´s take a look at the 2 bones that are involved. The hip is a ball and socket joint made up of the pelvis and femur, or thigh bone. Specifically, the ball is called the femoral head, and the socket is the acetabulum. The names of these 2 bones make up the word femoroacetabular.

Just like the shoulder, also a ball and socket joint, the hip has a labrum, a ring of cartilage that goes around the edge of the socket. Hip impingement is typically caused by an extra bump of bone that gets in the way of normal hip movement.

If the bump is on the ball side, it is called a Cam lesion and it is running into the edge of the socket. On the other hand, a bump on the edge of the socket is called a Pincer lesion, and it digs into the femur on the ball side. Hip impingement is a result of a Cam lesion, a Pincer lesion, or sometimes a combination of both.

These extra bony bumps pinch on the labrum over and over and eventually the labrum or sometimes even the surface cartilage in the socket can become damaged. This damage rarely happens from a one time injury. Chances are it develops over time instead.

So, who gets hip impingement?, and how do they know if they have cartilage damage? If we are talking about a Cam lesion where the bony bump is on the ball of the hip, that usually happens in young adult males anywhere from their late teens to early 30s. Pincer lesions, where the extra bone is on the socket side, are more common in young to middle-aged females.

That being said, anyone can get hip impingement, especially since sometimes it starts as a child. One of the growth plates in the hip is between the head and the neck of the femur. Sometimes, the growth plate is not strong enough to support the body weight of the child and the head or ball starts to slowly slide over the growth plate. Think of ice cream melting and starting to fall off the cone.

As the child grows, their growth plate closes and becomes strong, but the ball has already moved slightly. This is the bony bump that results, the Cam lesion. Symptoms of hip impingement are pretty standard across the board. Right off the bat, most patients will grab their hip with their hand in a C-shape like this, and simply say "it hurts right here." this is called the "C sign" for obvious reasons.

The majority of the patient's pain wraps around the front of their hip, sometimes deep into their groin area or down their thigh. This pain gets worse when the patient brings their knee up toward their chest, called hip flexion, and also when the patient turns their knee in, called hip internal rotation.

Patients will also say that the pain worsens with certain movements at work or being seated for long periods of time, like being on a long car ride or working all day at a computer. However, pain in this area can also come from tendinitis, which is completely different from hip impingement and would require different treatment.

Though not often, some patients may even have pain in their low back or backside, but this usually means there is something else going on, not hip impingement. It is important to have any hip pain looked at by a healthcare provider who specializes in hip problems to get an accurate diagnosis.

They will ask several questions, including where it hurts, when it hurts, and what kind of pain it is. During the physical exam, the healthcare provider will put the leg into the two motions described before, hip flexion and internal rotation, and see if they can recreate the symptoms that the patient is feeling.

They will move the hip in other directions also, as well as do a simple movement called the log-roll test to see how the ball rotates within the socket. Even though soft tissue and cartilage can not be seen on x-ray, seeing the shape of the hip bones can give a lot of information.

A normal hip x-ray should look like the shape of a light bulb: the same curve on the top and bottom. But on this x-ray, you can clearly see the extra bony bump on top of the ball, the Cam lesion. This is referred to as a pistol grip deformity.

The healthcare provider will also take several measurements from the x-ray. If there is suspicion of damage to the surface cartilage or labrum, an MRI will be ordered to take a closer look. The healthcare provider will likely order an injection to be done right before the MRI.

The injection is a liquid dye that shows up bright white on the MRI image. If the doctor sees bright white between the labrum and the bone, then there is a tear of the labrum. CT scans are taken only if the doctor needs a better look at the bones.