Our muscles are made up of strands of fibres, and these fibres are made up of threads of proteins called sarcomeres. Sarcomeres are the smallest unit of skeletal muscle cells, a single muscle cell contains about 100 000 sarcomeres, (a muscle cell is smaller than the diameter of a strand of hair). The sarcomeres are responsible for the movement of muscle contraction. However the problem begins when they contact and then instead of relaxing they stay contracted. Not much is known about why this may happen, but some possible causes are injury, stress, emotional and physical fatigue, poor postural habits or working positions. Perhaps it is just that the balance of the body has been disrupted for some reason and this is one way the body lets you know it needs some attention.
When these sacromere contract the fibres won't loosen, and it is for the likening of this to a tangled piece of rope that we call it a knot. When the fibres tighten the blood flow is restricted, and nutrients and oxygen have a tougher time getting into the belly of the muscle, and the waste has a tough time getting out. This lack of lubrication causes the muscles to become dry and the fibres to become even more entangled, imagine a tangled piece of rope, knotted when in the sea, and then left out in the sun, it dries and is ingrained with salt. This further irritates the sensory nerve endings, which increases the contraction and so perpetuates this cycle.
Massage breaks the cycle and through pressure starts to separate the fibres and untangle the knot, thus allowing fluids to move in and waste to move out. Increasing the circulation increases the oxygen and nutrients to the muscle and helps with the untangling process, additionally the sarcomeres are manually stretched and encouraged to stop contracting.