Help! Toddler hits head on crib from throwing herself backwards

My LO will be 17 months next week and she has recently started to throw her body backwards while in the crib. - she usually cries/whines herself to sleep, it seems to be her way of soothing herself and it normally doesn’t last longer than 5-10 min. However, the last few nights when I put her in the crib she’ll cry but then throws herself backwards - the problem is we have a solid back crib and she constantly hits her head when she falls. My husband and I can’t tell if it sounds worse than what it is but at times she cries harder after. It’s resulted in my taking her out and rocking her to sleep on me in the rocking chair which is not a habit I want to get into. Anyone else have a similar problem or suggestions on what we can do? We’re looking into ordering bumper pads for the back of the crib and figuring a way to make it work with the type of crib we have - at least to have something to soften the blow. I know that the arching and throwing backwards is normal for this age, my concern is just with her constantly falling backwards into the solid back of the crib and hitting her head. Thanks!