I am 5 feet 5 inches and am 12 What size should I get?

It all depends on the circumference of your knee. If you go to the McDavid website and look up this item, they will give you a size chart which tells (and shows) you exactly where and how to measure around your knees. You will need to use a measuring tape to get those measurements and then use the chart to determine the correct size. The sizing chart has been very accurate for us. You may need to take the measurements on both knees because one can often be larger than the other. Also, there is more than one type of leg sleeve with the number 6446, so make sure you get the right item with he right description because the sizing is different for each of them. This one says to measure around the largest part I your kneecap while standing with your leg bent at a 45 degree angle. You might need help for this. The sizing chart is based on your knee circumference: small= 10-12 inches; medium= 12-14 inches; large= 14-16 inches; XL= 16-19 inches; 2XL= 19-22 inches. But you should double check the website to make sure this is the pair you are purchasing and see the photo of how to measure your knee. Hope this helps.