A tight psoas can cause a similar snapping. The Thomas test can help determine if your psoas and other hip flexors are tight. There are a number of strategies to release a tight psoas.

Not sure about the knee aspect...I take it since you say ITB related that it's the outside (lateral) aspect of your knee that is affected? The psoas could definitely be an issue if your medial (inside) part of your knee is affected, as the adductors can also be playing a role. Where exactly is it that you feel the "catch"? The term hip can cover a lot of anatomy.