In the view that you do not have history of knee trauma, old or recent, then, knee popping or clicking might be due toto a muscle imbalance that makes your knee cap isn’t tracking properly in the joint. The quadriceps (the muscle group on the front of your thigh) is made up of four muscles. Your knee is popping because two of those four muscles are pulling over your knee cap and one of them is winning. The two muscles causing the knee popping are the vastus lateralis and the vastus medialis. The vastus medialis is on the inner-front part of your thigh and the vastus lateralis is on the outer-front part of your thigh. These two muscles connect on either side of your knee cap. In some people, for whatever reason, the vastus lateralis gets too strong or the vastus medialis gets too weak. As a result, the knee cap is pulled too far to the outside by the overly strong vastus lateralis and as the knee moves the knee cap isn’t gliding properly in the trochlear groove, causing knee popping, clicking, snapping, and other similar noises and sensations. In a healthy knee, the relative strength of the vastus lateralis and the vastus medialis is balanced and the knee cap slides up and down in the trochlear groove as it’s supposed to.
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