Even though it is often comfortable to slumber in what is referred to as the fetal placement, with legs curled up, this may make for an uneven distribution of bodyweight and produce back pain and sore joints. It could also lead to hip pain (hip bursitis) and shoulder pain, like https://www.theorthopaedicandpainpractice.com/the-best-sleeping-positions-to-relieve-neck-pain/