Testing lower extremity strength is a crucial part of the examination in patients with low back pain. In Emergency Departments, however, some patients provide a suboptimal effort because of general fatigue or malingering.
How can you differentiate whether asymmetric hip flexion weakness is from suboptimal effort or true weakness?
This test is an example of Newton’s 3rd law of motion — For every action there is an equal and opposite reaction.
A supine patient trying to flex a hip joint should normally push the contralateral heel downwards into the gurney for compensatory assistance. Absent downward pressure from the contralateral heel suggests a lack of effort, mimicking a focal weakness. You can optimize your ability to detect subtle contralateral downward pressure by cradling the patient’s heels in your palms during hip flexion testing.