If you constantly cross one leg over the other, knee over knee, you may eventually experience hip, low back, or sacroiliac joint (located between hip and low back) pain. Because we’re creatures of habit, we’re more likely cross the same leg over the other, which can lead to a muscular imbalance, or asymmetry. Asymmetries between the left and right are predictive of future injuries because they cause us to compensate for weakness, tightness, or limited range when we’re active.
In this example, crossing our leg knee over knee causes the inner thigh muscles (adductors) to contract while the outer hip muscles (abductors) are lengthened. The hip joint is also in a flexed position while it crosses the body’s midline, placing increased stress on the joint. The simple solution is to not cross the legs but if you have to, alternate between left and right.
A quick tip to improve sitting posture is to place a rolled towel directly behind your tailbone. This will prevent the hips from rotating backwards and place the low back in a neutral position. This position will help maintain spinal alignment. Ideally we should sit in a way where we slightly engage our core to maintain this neutral position without a towel. I like calling it “active sitting”.
If you experience discomfort when your cross your legs or just with sitting, it’s important to have a medical professional assess your mobility, strength, and any asymmetries and have them addressed to prevent future injuries.