Sleeping with a pillow between your legs is often not just a habit—it can be a response to the body’s alignment needs. In side sleeping, the hips and lower back can easily rotate, so some people naturally place a pillow between the knees to create a more balanced posture. Common practical reasons include reducing low-back strain, improving hip comfort, and preventing knee-to-knee pressure. Rather than assigning symbolic meaning, it is best understood as an ergonomic adjustment. If you cannot sleep without it, wake frequently, or have significant pain, consider evaluating mattress firmness, pillow height, and overall sleep posture together. A physiotherapist can provide tailored posture and sleep ergonomics guidance when needed.