Trendelenburg Sign

Context

The Trendelenburg Sign is often observed in patients with hip abductor weakness.

The Trendelenburg Test is a clinical screening test that measures pelvic stability in the frontal plane during single-leg stance. More specifically, pelvic stability in the frontal plane of the supporting limb can be quantified during the Trendelenburg Test by measuring the angle in the frontal plane formed by the pelvis to the femur (P-O-F angle) (Youdas et al., 2010; Kline et al., 2023).

A positive Trendelenburg Sign generally indicates weakness of the hip abductor muscles. These findings may be associated with various hip conditions, such as osteoarthritis or congenital hip dislocation (Hardcastle and Nade, 1985; Gogu and Gandbhir, 2024).

Video of the Test

Execution

To perform the test, the patient stands. They are asked to flex one hip to 30° and to stand on one leg for 30 seconds. They may hold on for balance if required (Hardcastle and Nade, 1985; Youdas et al., 2007, 2010; Kline et al., 2023).

The physical therapist assesses iliac crest heights bilaterally. Normally, the flexed hip side should be higher than the other side (Youdas et al., 2010).

Although the definition of a positive test can vary and is controversial, we consider this test to be positive when we observe a drop of the anterior superior iliac spine (ASIS) on the side opposite that of the supporting leg in the frontal plane. This would then indicate alterations in pelvic stability in the frontal plane (Asayama et al., 2002; Macnicol and Makris, 1991; Westhoff et al., 2006; Bailey et al., 2009; Kline et al., 2023; Gogu and Gandbhir, 2024).

Clinical Value

Some authors have specified that, with the use of a goniometer, an MDC of 3° or 4° would indicate hip abductor weakness (Youdas et al., 2007, 2010; Kline et al., 2023).

Youdas et al. (2010) assessed the validity of the Trendelenburg Sign for the diagnosis of hip osteoarthritis. They found a sensitivity of 55% and a specificity of 70%. The authors reported that the Trendelenburg Test (P-O-F angle) was not useful for identifying subjects in the early stages of osteoarthritis of the hip (Youdas et al., 2010).

The Trendelenburg Sign alone does not diagnose hip conditions, such as osteoarthritis or hip instability (Youdas et al., 2010; Gogu and Gandbhir, 2024). It has been shown to be more effective when part of a battery of tests in the physical examination, such as manual dynamometry and a good medical history to help assess hip abductor strength (Grimaldi, 2011; Gogu and Gandbhir, 2024). However, it is a quick and easy test that can help identify functional weakneses in the standing position.

Finally, in their 2023 study, Kline et al. reported that measuring the P-O-F angle with a goniometer during the Trendelenburg Test could provide important clinical information on hip abductor performance during gait and step transition in people with multiple sclerosis (MS). They found an MDC of 2.1° for this population.