Muscle nodules are usually formed for several reasons: 1. They may be caused by prolonged muscle spasm. This condition is often seen in patients who have been overusing a muscle for a long time, or who have had their muscles cooled. The former is often seen when the patient is in a fixed position for a long time, which leads to the long-term tension of certain muscles, which over time will produce some spastic muscle cords inside. The latter is common when the patient has insufficient clothing, resulting in a long period of cold, in this case, the muscle due to long-term cold will produce spasm, and then produce nodules. 2, may be due to muscle damage caused by. For example, if a patient strains a muscle during exercise, it may produce scarring when it recovers. These scars are the source of the subsequent muscle nodules. 3. It may be due to inflammation within the muscle. For example, if a patient has an injury, infection or cold inside the muscle, inflammatory exudate may be produced there. Such substances may produce adhesive tissues inside the muscle, thus creating internal nodules.