Ischiofemoral impingement (IFI) is a condition affecting the hip and pelvic region that can be a source of persistent pain. It involves the compression of soft tissues in a specific area of the hip, leading to discomfort and sometimes limited movement. Although it can be overlooked, understanding IFI is important for individuals experiencing hip pain.
Understanding Ischiofemoral Impingement
Ischiofemoral impingement occurs when soft tissues in the hip are compressed between two bony structures: the ischium (part of the pelvic bone, or “sit bone”) and the femur (thigh bone). The lesser trochanter, a bony prominence on the upper femur, moves too close to the ischial tuberosity. This narrowing pinches the soft tissues in the space between these bones.
The quadratus femoris muscle, a deep, square-shaped hip muscle, is primarily affected and helps externally rotate the hip. When the space between the ischium and femur narrows, this muscle can be pinched, causing irritation, inflammation, swelling, or even tears. The ischiofemoral space (IFS) is between the ischial tuberosity and lesser trochanter, while the quadratus femoris space (QFS) houses the quadratus femoris muscle. Impingement often occurs when IFS is less than 15 mm or QFS is less than 10 mm, though measurements vary.
Recognizing the Signs
Individuals with ischiofemoral impingement experience pain in the buttock, groin, or inner thigh. Pain is often deep, mimicking a pulled hamstring or sciatic nerve pain, and may radiate down the leg. Discomfort worsens with movements that narrow the ischiofemoral space, such as hip extension, adduction, and external rotation.
Pain increases with prolonged sitting or walking, particularly with longer strides. A shortened stride length may also occur. Other symptoms include stiffness, clicking, snapping, or locking in the hip, and occasionally numbness or tingling if the sciatic nerve is compressed.
Identifying the Cause
Several factors can contribute to ischiofemoral impingement, from anatomical variations or acquired conditions. A naturally narrower ischiofemoral space due to bone structure can predispose individuals to impingement.
Acquired causes include hip or pelvis trauma, such as fractures, which alter bone alignment. Degenerative changes like osteoarthritis can also contribute, leading to bone spurs or hip anatomy changes. Prior hip surgeries, including replacement, may also lead to IFI. Muscle imbalances, particularly weak hip abductor muscles, and repetitive hip extension movements in sports like running or dance, may also increase risk.
Diagnosis and Confirmation
Diagnosing ischiofemoral impingement begins with a patient’s symptom review and physical examination. During the physical exam, specific maneuvers like hip extension, adduction, and external rotation may provoke characteristic pain. The long stride walking test, which elicits pain with large steps, can also provide clues.
Imaging confirms IFI and rules out other conditions. Magnetic Resonance Imaging (MRI) is a primary tool for visualizing soft tissues, measuring ischiofemoral and quadratus femoris spaces, and showing impingement signs like swelling (edema) or fatty changes in the quadratus femoris muscle. X-rays show bone relationships but are generally used to rule out other bone problems, not definitively diagnose IFI. A diagnostic injection of local anesthetic into the ischiofemoral space can also confirm the pain source if it provides temporary relief.
Management Approaches
Management often begins with conservative, non-surgical approaches to reduce pain and inflammation. Rest and activity modification, such as avoiding prolonged sitting or certain movements, are recommended. Over-the-counter or prescription non-steroidal anti-inflammatory drugs (NSAIDs) manage pain and reduce inflammation.
Physical therapy is significant in conservative management. A tailored program focuses on strengthening hip muscles (including quadratus femoris and abductors), stretching tight muscles, and improving hip mechanics and gait. Corticosteroid injections into the ischiofemoral space, often imaging-guided, can also provide pain relief by reducing inflammation. If conservative measures are insufficient, surgical options include arthroscopic or open procedures to decompress the space by reshaping bony structures (e.g., reducing the lesser trochanter) or releasing tight soft tissues.