[header] How to treat anterior cruciate ligament (acl) tears [title] Rest your knee. [step] Start by sitting down to take any weight off of your knee. Sit on a comfortable chair or lie down with your knee elevated above your waist on a pillow or another, higher chair. 
Elevating your knee will help the swelling to go down. [substeps] Try not to move your knee at all or be up on your feet.