A. To understand what a knot is first you have to understand how a muscle normally works. Skeletal muscles (the muscles that move our bones) are made up of tiny fibers that wind together in bundles like an electrical cable. These tiny fibers have a complicated mechanism that allows them to “ratchet” against one another which makes the overall bundle shorter thus contracting the muscle. When a muscle is working perfectly all of these fibers work as one unit and pull together and release in order to tighten or relax a muscle. Unfortunately sometimes when a muscle gets injured or overused these fibers can get crisscrossed or damaged. When this happens you get a section of the muscle where the fibers get bunched up and stack on top of each other. That is what you feel when you rub a knot in a muscle.
Knots can cause problems in a muscle due to the fact that the normal mechanism for contracting a muscle hits a roadblock there and the overall muscle performance suffers. Due to the fact that fluids have a hard time entering and exiting from a knot you get a decreased blood supply to the area and you can also get a buildup of waste products like lactic acid which tends to be painful and irritating. Surprisingly enough when you have a knot in a muscle you can actually have pain in completely separate locations as well. An excellent example of this is knots in the muscles of the neck causing pain in the head. When knots refer pain to other locations they become known as trigger points. The reason that this happens is very complicated and still being researched but it is widely believed to be due to cross-wiring in the pain centers of the brain due to tissues developing at the same time when we are embryos/fetuses.
There are several ways to treat knots/trigger points. The simplest way is through pressure/massage. By pressing on the injured area you can break up the cross-linking fibers and squeeze out the waste built up. When the pressure is released blood rushes to the area re-oxegenating and healing the tissue. There are many different approaches and techniques that use pressure to release knots, and I find that a combination of approaches is generally the best way to go. One thing you can try at home however is to take a tennis ball and use it to press and roll on the area where you feel the knot. Obviously this works best on areas like your back or legs. Other than that a massage or a chiropractor is probably your best bet for getting rid of knots.