If you’ve ever banged your knee pretty badly, you might have noticed the knee swells up to larger than its normal size. To ease your pain and make the swelling go down, maybe someone handed you an ice pack. But why is it ice that does the trick to reduce swelling, and does anything else work? We asked physical therapist Karen Litzy to help us find the answer.

Got a Moment of Um question that’s making your brain swell? Send it to us at BrainsOn.org/contact, and we’ll help get it all sorted out.