The Figure 4 Test is a common orthopedic assessment used to help diagnose the source of pain in the hip, lower back, and sometimes the knee. This maneuver is widely known by its clinical acronym, the FABER test, which stands for Flexion, Abduction, and External Rotation of the hip joint. Healthcare providers use this simple, non-invasive test as a tool in the differential diagnosis process to determine if a patient’s symptoms originate from the hip joint, the surrounding soft tissues, or the sacroiliac (SI) joint.
Performing the FABER Maneuver
The FABER maneuver is performed while the patient lies face-up (supine) on an examination table. The examiner begins by passively moving the patient’s leg on the side being assessed. The hip and knee are flexed, and the ankle of the tested leg is placed on the opposite thigh, just above the kneecap. This positioning creates the distinct “Figure 4” shape, lending the test its common name.
The examiner stabilizes the pelvis on the opposite side to prevent rotation, typically by placing one hand on the anterior superior iliac spine (ASIS) of the non-tested side. With the pelvis stabilized, the examiner applies gentle, sustained pressure downward on the inside of the bent knee. This pressure pushes the hip joint into further abduction and external rotation, stressing the joint capsule and surrounding ligaments.
The examiner observes the range of motion of the tested hip and notes if the knee drops close to the examination table. The patient is asked to report any pain or discomfort and specify the exact location of the sensation. For a complete assessment, the healthcare provider performs the test on the unaffected side first, comparing the range of motion and any differences in pain response between the two hips.
The Connection Between Hip Pathology and Knee Pain
While the Figure 4 Test primarily focuses on stressing the hip and sacroiliac joints, it is frequently used in the evaluation of knee pain because hip issues can often be mistakenly felt in the knee. Pain originating from the hip joint is sometimes perceived as being located in the inner thigh or around the knee. This phenomenon is known as referred pain, where the discomfort is felt at a site different from the actual source of the problem.
Conditions affecting the hip joint, such as osteoarthritis, labral tears, or femoroacetabular impingement (FAI), commonly manifest with symptoms that extend down the leg. For instance, a patient with significant hip osteoarthritis might feel a deep ache in their knee, even if the knee joint itself is healthy. Tightness in powerful hip flexor muscles, like the iliopsoas, can also be stressed by the FABER position and contribute to referred pain patterns.
The diagnostic utility of the FABER test in the context of knee pain is its ability to help rule out the hip as the true source of the patient’s discomfort. If the test reproduces the patient’s familiar knee pain, it strongly suggests the issue is rooted in the hip or pelvis, and the knee is simply receiving referred pain signals. This finding directs the clinician away from treating the knee and toward a more appropriate evaluation and treatment of the hip joint.
What a Positive Result Indicates
A positive result on the Figure 4 Test is generally defined by two key findings: the reproduction of the patient’s familiar pain or a significantly restricted range of motion. If the tested knee remains elevated well above the level of the opposite leg, or if pain prevents the full range of movement, the test is considered positive. The precise location of the pain elicited offers the most specific clinical information for diagnosis.
If the patient reports pain deep in the groin or the anterior aspect of the hip, this strongly suggests a problem within the hip joint itself. This finding points toward intra-articular hip pathology, which may include osteoarthritis, a labral tear, or mechanical impingement. The FABER position compresses and stresses the structures inside the joint socket, making it sensitive to these issues.
In contrast, if the pain is felt in the posterior hip, the buttock, or over the sacrum, it indicates dysfunction of the sacroiliac (SI) joint. The FABER test creates a torsional stress on the SI joint, which can provoke pain if the joint is inflamed or unstable. A negative result, where the hip has full range of motion and the knee drops close to the table without pain, is a strong indicator that neither the hip joint nor the SI joint is the primary source of the patient’s pain.