What exactly is a small hemipelvis? The pelvis is made of two bones that come together with ligaments. In some people one of these bones is smaller than the other causing a plethora of problems. When sitting it makes the body tilt towards the smaller side, sometimes mimicking scoliosis since it causes the spine to curve to compensate. When standing, it seems like the legs are two different lengths. It can cause lower back pain, hip pain, leg pain, neck pain, shoulder pain and jaw pain. To fix this problem you can sit with something under the smaller side like a magazine.
Luckily there are fixes for this. You can get an insert for the shoe of the small side of the pelvis and you can carry a magazine or book to sit on under the small side. Massage and acupuncture can help tremendously with the pain caused by this. People with a small hemipelvis will feel the need to cross their legs to compensate. Here is a video that can help you figure out if you have a small hemipelvis.