Leg stuck in crib??

b

What a way to start the year. My daughter bent her knee and got it stuck in between the crib slats. I managed to get it out. Got there right away bc she started screaming. It left a terrible bruise. Never in my life would I have thought she'd do it again. Well she did. And it was so bad my husband couldn't get her leg out. Her foot started turning blue so he had to saw off the crib slat. Needless to say we were all very traumatized. How tf does that happen that badly. How can I prevent it? This is a nice ass crib from pottery barn.