Remember this song from when you were little: "The thighbone's connected to the hipbone"? Well, the song may be silly, but one thing is true: A good, stable connection at your hip joint is what lets you walk, run, make that jump shot, and shake it on the dance floor.

But in some teens — particularly those who are obese — the thighbone and the hipbone are a little less well connected than they ought to be because of a condition called slipped capital femoral epiphysis (SCFE).

Though the name's quite a mouthful, it simply refers to a shift at the upper part of the thighbone, or femur, that results in a weakened hip joint. Fortunately, when caught early, most cases can be treated successfully.

What Is Slipped Capital Femoral Epiphysis?

To understand SCFE, you first have to know a little about the hip joint. The hip is a ball-and-socket joint, which means that the rounded end of one bone (in this case, the "ball" of the thighbone) fits into the hollow of another bone (the pelvis). Ball-and-socket joints offer the greatest range of movement of all types of joints, which is why you can move your legs forward, backward, and all around.

For a teen who is still growing, there is also a growth plate at the top of the thighbone (femur), just under the "ball" portion of the joint. This is called the epiphysis, and it's made out of cartilage, which is weaker than bone. The job of the epiphysis is to connect the femoral head (the "ball") to the femur while still allowing the bone to lengthen and grow.

When a teen has SCFE, the epiphysis slips off of the top part of the femur, almost the way a scoop of ice cream might slip off a cone. Sometimes this happens suddenly — after a fall or sports injury, for example. But it can also happen with what seems like no reason, with no previous injury.

A mild slip (what doctors call a stable SCFE) causes a person to feel stiffness or pain in the knee or groin area, and possibly to develop a limp. The pain and the limp typically tend to come and go, worsening with activity and getting better with rest.

A more severe slip (called an unstable SCFE) is usually much more painful. The person might not be able to put weight on the affected side. Because the joint can't move as much, the person's foot and leg may begin to turn outward. An unstable SCFE is also serious because it can restrict blood flow to the hip joint.

Sometimes SCFE can irritate the nerves that run down the leg and can cause knee pain. This type of pain is called referred pain, which means pain originates in one part of the body but is felt in another part. In this case, pain originates in the abnormal hip joint but is felt in the normal knee joint.

Catching SCFE early makes a big difference in how easily doctors are able to treat it.

What Causes It?

No one knows for sure what causes SCFE. Doctors do know that it mostly happens in people between the ages of 11 and 16 who are going through a growth spurt. SCFE is more common in guys, though girls can have it too. Sometimes a person has a family history of SCFE.

SCFE is also more likely to happen to teens who have specific stuff going on with their health, such as:

• obesity (carrying extra weight puts increased pressure on the growth plate)
• endocrine disorders like diabetes, thyroid disease, or growth hormone problems
• kidney disease
• treatments for disease, like radiation and chemotherapy for cancer or taking certain medications, including steroids

How Is It Diagnosed?

If a doctor thinks you may have SCFE you'll need to see an orthopedic doctor (a doctor who specializes in the treatment of bones), who will do a physical exam, checking the range of motion of the hips and legs and seeing if there is any pain. He or she will also take X-rays of the hip to look for a displacement at the head of the thighbone.

Sometimes, though, the X-rays will come back normal but the pain, stiffness, and other problems will still be there. In these cases, a magnetic resonance imaging study (MRI) or bone scan will likely be ordered. Both of these tests work like X-rays but are more sensitive and show more. The MRI, in particular, has the ability to highlight contrasts in soft tissue, which makes it especially useful in deciphering problems with joints and cartilage.

How Is It Treated?

SCFE is always treated with surgery to stabilize the bone that slipped. But even before the surgery, the doctor will try to prevent any further slippage by recommending lots of rest and the use of crutches to avoid putting weight on the affected leg.

With milder slips, the surgery is often done as an outpatient procedure, which means a patient can leave the hospital the same day or the day after the surgery if there are no complications. More severe slips may require more extensive surgery and a longer hospital stay.

The surgery is performed under general anesthesia (when a patient is completely asleep). Using a fluoroscope — a special X-ray machine that produces a real-time image of the hip on a TV screen — as a guide, the surgeon will make a small incision near the hip. He or she will then put a metal screw or pin through the bone and the growth plate to hold it in place. Sometimes the surgeon will stabilize the other side as well, even if it hasn't slipped yet, just because the risk is high that it could happen. More severe slips may require further repositioning of the hip.

After surgery, patients are allowed to walk with crutches, only putting some of their weight on the affected leg. Patients who have both hips treated usually need to use a wheelchair for the first couple of weeks after surgery.

After Surgery

Most teens whose SCFE is caught and treated early do well. Patients often get physical therapy after surgery to strengthen the hip and leg muscles. Doctors will continue to order follow-up X-rays to monitor the condition. But in most mild cases, further surgery is not needed.

Teens with unstable SCFE, however, do have a greater chance of developing other problems, such as stiff hips, early arthritis, leg length differences, or avascular necrosis (where part of the "ball" dies from lack of blood supply). They're also more likely to require additional surgery to realign the hips as they grow.

Not everyone can prevent SCFE. But one thing you can do to lessen your risk is to keep your weight in a healthy range. Maintaining a healthy weight can go a long way in sparing your bones and joints from the excess wear and tear that can weaken and damage them. So if you need help figuring out how to start on a safe diet and exercise plan, talk to your doctor.

Reviewed by: Alfred Atanda Jr., MD
Date reviewed: April 2010