For many athletes and dancers, the hip joint can be a source of great power and stability, allowing them to excel in their craft. The hip is stabilized by over 15 different muscles and has the capacity to be stretched into extreme ranges of motion, such as during a ballerina’s overhead leg extension or a first baseman’s stretch.
This large, complex, and highly flexible joint also carries a great risk of injury, especially when pushed to anatomical extremes. A hip injury can be a source of nagging pain and discomfort that can be difficult to diagnose, given the complexity of the hip. One of the possible sources of hip pain is femoroacetabular impingement, or FAI, which is common in high-level athletes and active individuals. This common diagnosis is complicated by its relatively unknown cause.
In this article, we’ll cover the anatomy of femoroacetabular impingement, what causes it, the symptoms associated with it, and possible treatment options.
Anatomy of the hip and implications of FAI
The hip joint (ball and socket) consists of the femoral head (ball), which is the top end of the long bone of the thigh, and the acetabulum (socket), which is attached to the pelvis. The acetabulum is covered with articular cartilage, which allows for smooth movement in the joint, as well as a labrum, which is a strong, fibrous cartilage that lines the outer rim of the socket. The labrum helps to deepen the hip socket and allows for greater range of motion in the joint.
In patients with femoroacetabular impingement (FAI), the contact between the femoral head and the acetabulum is abnormal during movement, causing pinching of soft tissue (labrum or cartilage) and excess friction within the joint. FAI can result in damage to these soft tissue structures, subsequent pain, and the possible development of hip arthritis at an early age.
What causes FAI and who is affected?
The abnormal contact in the hip joint associated with FAI can be due to one of two forms of FAI, known as Cam and Pincer. Often these two forms of FAI exist together.
In the Cam form, the femoral head and neck are not perfectly spherical, causing abnormal contact between the femur and the acetabulum during movement. In the Pincer form of FAI, the acetabulum over-covers the femoral head, usually occurring along the front-top rim of the socket. With Pincer FAI, the socket can also be angled backwards more than it should be (retroverted) or could be deeper than normal, leading to abnormal over coverage of the femoral head.
This abnormal anatomy and malalignment during movement can damage the cartilage and labrum of the hip, possibly leading to arthritic changes in the hip at an early age. The Cam form of FAI often affects young male athletes, while the Pincer form is more common in middle-aged female athletes. FAI affects athletes across many different sports, including martial arts, ballet, football, baseball, soccer, and cycling.
The cause of femoroacetabular impingement continues to be under investigation. Some proposed theories include participation in high-impact sports during adolescence, genetic predisposition, and history of pediatric hip disease.
Symptoms of FAI
Most people with FAI experience pain in the front of the hip that can be felt in the groin. Sometimes the pain can radiate down the front of the thigh. Oftentimes, patients will cup the outside of their hip with their hand in a “C” position to describe the deep pain location associated with FAI. This is known as a “C” sign. Patients with FAI may also experience low back pain, buttock pain, or pain at the side of the hip.
Prolonged sitting, such as while driving, or deep squatting can increase pain in a patient with FAI. This is because hip flexion (bringing the thigh up to a 90-degree angle with the trunk) can cause anterior impingement or abnormal contact at the front of the hip joint that can pinch the cartilage and labrum. Other daily activities that involve hip flexion include putting on socks and shoes and walking up a hill, and these may also be a source of pain in patients with FAI.
If damage to the cartilage or labrum has already occurred, the patient may experience a “clicking” or “catching” sensation in the hip during movement.
In addition to discussing your pain pattern, a physical therapist will assess your hip strength, hip range of motion, and observe your gait, or walking pattern. Oftentimes, hip flexion and hip internal rotation (turning the toes inwards when the leg is straight) are restricted in patients with FAI.
Treatment options for FAI
If your physical therapist suspects FAI based on your clinical examination, they will refer you to your primary care physician for X-rays. If the X-ray suggests abnormal bony anatomy, your physician may order an MRI to assess the soft tissue damage.
Although physical therapy will not change the bony anatomy of your hip, it can be beneficial in addressing the symptoms associated with FAI and is almost always recommended as the initial treatment. A physical therapist can help you to improve your hip strength, increase your flexibility, and retrain movement patterns which may have been contributing to your pain. They can also offer strategies for conservative pain management and lifestyle modifications, such as activity avoidance.
Here are five easy exercises that you can do to help manage FAI:
- Hip flexor stretch: Kneel on your left knee and place your right foot in front of you, with your knee bent at a 90-degree angle. Lean forward into your right hip until you feel a stretch in the front of your left hip. Hold for 30 seconds and repeat on the other side.
- Clamshells: Lie on your left side with your knees bent and your feet together. Keeping your feet together, lift your right knee as high as you can without moving your pelvis. Lower your knee and repeat for 10-15 repetitions. Repeat on the other side.
- Hip bridges: Lie on your back with your knees bent and your feet flat on the ground. Lift your hips up towards the ceiling, squeezing your glutes at the top of the movement. Lower your hips back down and repeat for 10-15 repetitions.
- Side-lying leg lift: Lie on your left side with your legs straight. Lift your right leg as high as you can without tilting your pelvis. Lower your leg and repeat for 10-15 repetitions. Repeat on the other side.
- Quadruped hip extension: Get down on all fours with your hands under your shoulders and your knees under your hips. Lift your right leg behind you as high as you can without arching your back. Lower your leg and repeat for 10-15 repetitions. Repeat on the other side.
Remember to start slowly and gradually increase the intensity and duration of the exercises as you become more comfortable with them. It’s always a good idea to consult with your physical therapist before starting any exercise program.
There are minimally invasive and open surgical options for treating FAI. Be sure to discuss both of these options with your surgeon to determine the right course of treatment for you. Both surgical options aim to correct bony abnormalities and repair cartilage or labral damage. The ultimate goal of FAI surgery is to halt degenerative changes within the hip and prevent hip osteoarthritis. The success of surgery is often dependent on the amount of joint damage prior to surgery, making early detection and care crucial in patients with FAI.
The minimally invasive procedure uses an arthroscope to repair the soft tissue damage, stimulate new cartilage growth (through microdamage), and remove bone (decompression). The arthroscopic procedure is typically done at an outpatient center and the patient returns home the same day. One recent study found that arthroscopic surgery for FAI yielded significant reductions in pain and functional improvements within one to two years after surgery . However, the minimally invasive procedure is not right for everyone and is more likely to fail in patients with advanced hip arthritis.
The open surgical option involves a hip dislocation and the patient must remain in the hospital for a few days after surgery. You can expect to be on crutches after your surgery, with a total recovery time of 4-6 months for both procedures. After a full recovery, you may be cleared to return to unrestricted physical activity, however, this is dependent on the type of surgery you underwent and the condition of your hip joint prior to surgery.
Femoroacetabular impingement (FAI) is a common cause of hip pain in adolescents and adults and is often seen in high-level athletes. FAI is due to abnormal bone structure of the hip and resulting impingement of the hip cartilage and labrum, which produces pain during certain positions or activities. One of the biggest concerns with FAI is its acceleration of degenerative changes in the hip, which can lead to hip osteoarthritis. Early identification and treatment of FAI is key for optimal recovery. Physical therapy is typically the first line of treatment for FAI to conservatively manage symptoms. Minimally invasive and open surgical options exist and can correct the bony anatomy and soft tissue damage. Research has shown significant pain reduction and functional improvement after minimally invasive procedures in patients with minimal joint damage.