Hemming knits can be tricky. The very stretch that makes it easy to get a good fit on a garment can make a stretched out, wavy hem. But it is possible to get a clean non-wavy hem on knit fabrics, and actually you have a number of options. Craftsy shares a post on their blog giving 5 ways to hem knit fabrics. The best one to use will vary by the type of knit, the style garment, and the tools you have on hand. Go to their post to see 5 options for hemming knits.
[photo from Craftsy]