I'm a massage therapist. Knot is really a catch-all with no definition, which causes a lot of confusion. A person is often referring to the phenomena of trigger points, but the plain truth is that very few people who have "knots" have trigger points in my experience. There's a distinct texture to a trigger point and pattern of response, and the method to release a trigger point is different from what you'd use on generalized muscle tightness. In most cases people that come to me complaining of knots just have a generalized muscle tightness caused by poor posture exacerbated by either lack of movement or lack of movement variety. I see 2-3 dozen or so new clients a month, outside of my regulars, and I'd say that I encounter a proper trigger point maybe twice a month on average or less. My specialty is in myofascial massage utilizing structural integration techniques and philosphy, so it would stand to reason that I'd be more likely to encounter people with trigger points since they'd self select, right? (Structural integration is a somewhat broad subset of myofascial massage with the intent of balancing the relative tension between muscular groups in order to relieve pain or increase range of motion, usually through utilization of targeted stretching, active/passive mobilization, and targeted deep tissue work)

Personally, I think the word knot is overused, to the detriment of people's health. What is implied when a professional uses the word knot is that there's something wrong, some sort of physical thing that needs to be untangled by someone else (or even worse, something that just is an aspect of you, like the color of your skin or your height) instead of a temporary state of affairs that can be improved by yourself. Especially when it's actually just general muscle tightness. A professional can help short term, but generally targeted stretching and exercise, with some mild lifestyle changes, is the cure. A person sitting at a computer 6-8 hours a day doesn't need someone to hammer their upper back/shoulders with their elbow (though it will feel good and provide short term relief), they need to sit still for shorter periods, stretch their pec minor, and do some band pull aparts/face pulls/rows/lat pulldowns.