Complex sentence: A fist X-ray of a scapholunate ligament rupture will show a descending capitate bone, because when you make a fist it will give pressure at the capitate bone, which will descend if there is a rupture in the scapholunate ligament.
Split into simpler sentences: A fist X-ray of a scapholunate ligament rupture will show a descending capitate. Making a fist will give pressure at the capitate, which will descend if there is a rupture in the scapholunate ligament.