Diagnosing Hip Impingement Syndrome

Hip impingement syndrome, also called femoroacetabular impingement, occurs when there is unusual contact between the bones of the hip joint, preventing the joint from having a smooth range of motion. Doctors at NYU Langone’s Joint Preservation and Arthritis Center specialize in diagnosing this condition and use advanced imaging tests to identify the cause of hip impingement.

In a healthy hip joint, the femoral head, which is the rounded top of the thighbone, fits perfectly into the acetabulum, a bowl-shaped depression in the lower pelvis. These bones are lined with a tissue called cartilage that provides a smooth gliding surface for the joint. A protective ring of cartilage called the labrum surrounds the hip joint and forms a tight seal, helping to keep the femoral head in place.

If the femoral head or acetabulum is not perfectly round, it may prevent smooth motion in the joint and create friction between the bones and the labrum. Over time, this contact may cause a labral tear or damage adjacent cartilage, leading to osteoarthritis.

Hip impingement is considered a prearthritic condition. Early diagnosis is key to starting treatment before cartilage damage is severe.

Hip impingement syndrome often affects active people 20 to 40 years old with no history of hip injury. Some people don't feel any symptoms, even if they've had the condition for years.

If symptoms begin to occur, it usually means that there is some damage to cartilage or the labrum. Symptoms include a dull, aching pain in the groin that may get worse during movement and exercise, the sensation or sound of clicking or popping in the hip joint during movement, and stiffness in the thigh, hip, or groin.

Types of Hip Impingement Syndrome

Doctors have identified three common types of hip impingement syndrome: cam impingement, pincer impingement, and combined impingement.

Cam Impingement

When the ball-shaped femoral head is not perfectly round, cam impingement may occur. An irregularity in the shape of the femoral head—for example, a protruding bone growth—prevents it from moving smoothly within the hip socket.

Pincer Impingement

When bone growth causes the socket-shaped acetabulum to extend too far over the ball-shaped femoral head, it can lead to pincer impingement. If the rim of the hip socket sticks out, it may pinch the labrum during movement and cause it to tear.

Combined Impingement

Most people experience either cam impingement or pincer impingement. However, it’s possible to experience combined impingement, in which both conditions develop in the same hip joint.

To diagnose hip impingement syndrome, doctors at NYU Langone conduct a medical history and perform a physical exam. In addition, they use highly sensitive imaging tests to confirm the presence of a bone growth and impingement in the hip joint. Imaging can also confirm whether there is damage to cartilage in the hip joint.

Medical History

Doctors ask about when the pain, stiffness, or dysfunction began, where the pain is located, what movements are most painful, and how much these symptoms interfere with your daily activities and lifestyle.

In addition, doctors need to know whether you have any underlying medical conditions. For example, the hip does not form correctly in many people born with hip dysplasia. They also want to know if these medical conditions require medication.

Be sure to tell your doctors if you’ve had hip surgery or a previous injury to the hip. These and other details help doctors assess your treatment options.

Physical Exam

Our doctors examine your hip to determine if any physical signs suggest hip impingement syndrome. Doctors may gently move your hip in different ways in order to assess the range of motion.

You may also be asked to walk back and forth a few steps, so doctors can see if impingement is causing any changes in your gait, such as a limp. Doctors also gently press the skin outside of the hip joint to check for tenderness or a lump or knob in the joint area. 

Imaging Tests

Our doctors may recommend one or more diagnostic imaging tests to confirm the presence of bone spurs or joint damage caused by impingement. These tests are painless and take place at NYU Langone.

X-rays

X-rays are two-dimensional images created by high-energy beams of light. Doctors at NYU Langone often take several X-rays to obtain multiple views of the bones in the hip joint.

You may be asked to rotate your hip in different ways, so images of the joint can be taken from different angles. These X-rays reveal structural abnormalities in the hip joint, including a nonspherical femoral head or an overly extended acetabulum.

MRI Scans

MRI scans use radio waves and electromagnetic fields to create computer-generated images of the inside of the body. In particular, MRI scans provide detailed pictures of soft tissues, such as cartilage and the labrum.

Doctors and radiologists at NYU Langone use three-dimensional MRI technology, which provides images of the hip joint from every angle. They are experienced in newer MRI techniques designed specifically to detect cartilage breakdown in joints, including the labrum. These enhanced techniques can be used during a regular MRI scan. For example, doctors may modify the sequence of electromagnetic pulses generated during the MRI to create images of cartilage within the joint.

Sometimes the doctor injects a contrast dye into the bloodstream or into the hip joint before the MRI scan is performed. This dye enhances the visualization of cartilage in the hip.

MRI Scans of Cartilage

Doctors and radiologists at NYU Langone use new MRI technologies designed specifically to detect cartilage breakdown in joints, including the labrum. These enhanced techniques can be used during a regular MRI scan. For example, doctors may modify the sequence of electromagnetic pulses generated during the MRI to create images of cartilage within the joint.

Another technique uses a contrast dye that is injected into the bloodstream or into the hip joint before the MRI scan is performed. This dye enhances the visualization of cartilage in the hip.

CT Scans

CT scans use a series of X-rays to create detailed images of bony structures within the body. Computers then combine these images into two- and three-dimensional images that can be examined from a variety of angles.

NYU Langone doctors use advanced CT technology that requires the least amount of radiation possible to get a better look at the way the femoral head fits into the acetabulum.

Diagnostic Injection

Occasionally, your doctor may recommend injecting a small amount of anesthetic directly into the hip joint. This can confirm that hip pain is caused by impingement in the joint.

Hip pain has many causes, and symptoms that seem to indicate hip impingement syndrome may be caused by a different condition. If anesthetic injected into the joint immediately relieves pain, it’s likely that a problem in the hip joint is the cause of your symptoms.

Doctors use live ultrasound guidance—an imaging technique that uses high-frequency sound waves to create images of the inside of the body—or X-rays to ensure the anesthetic is injected precisely into the hip joint space. This diagnostic test is done in the doctor’s office or radiology suite and takes less than an hour.

After leaving the doctor’s office, you are asked to monitor your body’s response to the diagnostic injection for several hours. Our doctors suggest that you stand and walk every 30 minutes and write down whether the pain feels better, worse, or the same. This information helps our doctors to confirm the diagnosis.