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Anatomy of the Hip Joint
The hip joint is a ball-and-socket joint comprising the femoral head and the acetabulum located in the pelvic bone (formed by parts of the ilium, pubis, and ischium). These surfaces are covered by a strong, smooth material called articular cartilage, which allows the joint surfaces to glide smoothly against each other during hip movements. The anatomical structure of the hip joint enables flexion, extension, abduction, and both internal and external rotations of the lower limb.
A crucial component of the joint is the labrum, which encircles the outer edge of the acetabulum, deepening the socket. This enhances joint stability, absorbs shocks, and provides some flexibility. The hip joint is surrounded by a joint capsule filled with synovial fluid and reinforced by ligaments. Muscles around the hip play a vital role, comprising opposing groups that balance each other’s actions. If one of these groups becomes dominant, the hip joint may lose its proper alignment, potentially leading to femoroacetabular impingement (one of the theories explaining the causes of FAI).
Causes of Femoroacetabular Impingement
There are many causes of hip joint pain, one of which is femoroacetabular impingement (FAI). This condition was first described in 2003 as a repetitive abnormal contact between the acetabulum and the femoral head, which can lead to degenerative changes and damage to the articular cartilage and labrum.
FAI is caused by abnormal bone growth, which may occur in the femoral head, acetabulum, or both.
Cam Impingement: This occurs when a bony deformity develops at the junction of the femoral head and neck. This protrusion may hinder full rotation of the femoral head within the acetabulum or rub against the labrum and cartilage, causing damage. Statistics indicate that Cam impingement most commonly affects young men and is less frequent in women.
Pincer Impingement: This occurs when a bony deformity forms on the edge of the acetabulum. The resulting overhang deepens the socket in some areas, limiting the femoral head's rotation or damaging the labrum. Pincer impingement is most common in middle-aged women.
Mixed Impingement: Many individuals exhibit mixed impingement, where both Cam and Pincer types coexist.
Patients with FAI often report no history of trauma to the orthopedist. These are generally young, physically active individuals whose symptoms emerged after changing sports disciplines or introducing specialized exercises that irritate the groin area. Notably, there is a strong association between FAI and hip osteoarthritis. When the femoral head and acetabulum do not fit together properly, the articular cartilage covering these surfaces may experience excessive friction, leading to significant wear and eventual damage.
Symptoms of Femoroacetabular Impingement
Symptoms of FAI vary among individuals but typically develop gradually and worsen over weeks or months.
The most common symptom is hip joint pain combined with reduced range of motion, particularly during internal rotation of the hips.
Patients often describe sharp groin pain during squatting or twisting movements of the lower limb.
Symptoms are usually intermittent, appearing and disappearing.
A characteristic symptom is sudden, stabbing pain while getting in and out of a car or standing up from a chair, especially after prolonged sitting.
The hip joint may occasionally pop or partially lock due to labral damage.
Some individuals report dull pain after long walks, which can become severe enough to hinder walking, giving the impression of dragging the leg. Stiffness around the hips, reduced hip range of motion, and changes in gait, especially when climbing stairs, are common. Older individuals may experience reduced muscle strength around the hips, affecting balance.
Diagnosing Femoroacetabular Impingement
The symptoms described above are often so characteristic that patients may self-diagnose the condition. However, proper diagnosis should only be made by an orthopedic surgeon or physiotherapist. Diagnosis begins with a patient interview to identify any previous injuries or surgeries, when the symptoms started, how they began, and which movements cause pain.
The physician then conducts a physical examination, including three primary tests to provoke hip pain and assess range of motion limitations:
FABER Test (Flexion, Abduction, and External Rotation): The patient lies on their back, and the physician moves the tested leg into abduction with the foot resting on the opposite leg.
FADDIR Test (Flexion, Adduction, and Internal Rotation): The patient lies on their back while the physician lifts the lower limb, flexing the knee and hip to 90 degrees, then rotates the knee inward and adducts it.
Posterior Impingement Test: The patient lies on their back with the hip joint positioned at the edge of the table. The physician abducts the leg and performs external rotation.
Imaging plays a vital role in diagnosing FAI. X-rays can confirm the condition by revealing bony deformities on the femur and/or acetabulum. Magnetic resonance imaging (MRI) with contrast (arthrography) may also be used to detect labral damage.
Treatment of Femoroacetabular Impingement
The foundation of FAI treatment is non-surgical management, which has gained importance in recent years. Patients are advised to modify their physical activities, avoiding extreme hip joint movements that exacerbate symptoms. It is essential to work with a physiotherapist to strengthen the muscles around the hip and improve hip joint biomechanics. If rest and physiotherapy fail, physicians may recommend nonsteroidal anti-inflammatory drugs or injections with platelet-rich plasma (PRP) or stem cells.
For active individuals unwilling to modify or quit their sports activities, surgical intervention may be the only option. The type of surgery depends on the underlying cause of FAI and the associated soft tissue damage.
Osteochon.droplasty with Joint Dislocation: Provides excellent visualization of the entire acetabular rim and allows simultaneous reconstruction of the damaged labrum.
Osteochon.droplasty without Joint Dislocation: A minimally invasive anterior approach that minimizes muscle trauma and facilitates a quicker recovery.
Hip Arthroscopy: A minimally invasive alternative with a shorter recovery period and earlier rehabilitation. During the procedure, bony tissue causing FAI is removed, and damaged labral tissues are repaired.
In most cases, surgery reduces pain and improves hip joint functionality. However, outcomes may be less favorable in patients with hip arthritis symptoms or older individuals.
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