The Trendelenburg test is a common clinical assessment in orthopedics, evaluating hip strength and stability. It helps identify weaknesses in pelvic stabilizing muscles, which can impact walking ability. This test provides insight into hip function mechanics and can indicate various conditions affecting the hip joint and surrounding musculature.
Understanding the Trendelenburg Test
This physical examination maneuver assesses the function of hip abductor muscles, particularly the gluteus medius and gluteus minimus. These muscles maintain a level pelvis during single-leg stance, preventing the opposite side from dropping. The test identifies weakness or dysfunction in these muscles, crucial for stable walking and diagnosing gait abnormalities.
Performing the Test
A healthcare professional instructs the patient to stand on one leg, unassisted, though they may hold onto support for balance. The examiner observes the patient from behind, focusing on pelvic alignment, specifically the iliac crests. The patient lifts one foot off the ground, flexing their hip and knee to clear the floor. This action places body weight onto the standing leg, requiring its hip abductor muscles to engage and stabilize the pelvis.
Interpreting the Results
A “positive” Trendelenburg test occurs when the pelvis on the side opposite the standing leg drops or sags. This dropping of the contralateral (unsupported) hip indicates weakness in the hip abductor muscles of the stance (weight-bearing) leg. The gluteus medius and gluteus minimus muscles on the standing side are not effectively contracting to keep the pelvis level. Conversely, a “negative” test means the pelvis remains level or even rises slightly on the unsupported side, signifying adequate strength and function. While slight elevation of the unsupported pelvis can be normal, a significant drop points to a functional deficit.
Common Causes of a Positive Test
A positive Trendelenburg test often indicates weakness or dysfunction of the gluteus medius and gluteus minimus muscles, which are innervated by the superior gluteal nerve. Weakness can stem from various issues, including damage to the superior gluteal nerve (due to trauma, compression, or hip replacement surgery). Hip joint conditions like osteoarthritis, hip dysplasia, or chronic dislocations can also lead to a positive sign by impairing abductor muscle mechanics or causing pain.
Additionally, direct muscle injury or atrophy of the gluteus medius and minimus (e.g., from tendinitis or abscesses) can result in insufficient pelvic stabilization. Systemic conditions like poliomyelitis or muscular dystrophy may also manifest with a positive sign. A positive Trendelenburg test signifies hip abductor insufficiency, but it is not a definitive diagnosis and warrants further medical evaluation to determine the precise cause.