The common causes of knee pain in adolescents may be physiological factors such as growing pains and exertion, or pathologic factors such as meniscus injury and epiphyseal inflammation. 1. Physiological factors (1) Growing pains: these are recurrent, episodic and intermittent lower limb pains occurring in healthy children between 2 and 12 years of age, especially around the knee joint and anterior side of the calf. The pain can be relieved on its own without any treatment, and the symptoms can be reduced or disappear as the bones mature. (2) Exhaustion: The accumulation of lactic acid due to the production of metabolic products in the body caused by prolonged exercise can lead to pain in the soft tissues around the knee joint, which can be gradually relieved with proper rest. 2. Pathological factors (1) Meniscus injury: teenagers are usually more active, when the lower limbs for a long time excessive activities or improper exercise, may lead to meniscus injury of the knee joint, the most common symptom is pain when walking or exercising, and sometimes there may be the sound of clicking in the knee joint when squatting up and down, and there may be the symptom of joints suddenly jammed and unable to move or the joints are weak all of a sudden. (2) Epiphyseal inflammation: Epiphyseal inflammation is a disease in which a part of the bone is necrotic due to an abnormality in the blood vessels that deliver nutrients to the bone during the developmental stage, and it is most common in adolescents. Typical symptoms include pain in the inflamed area, muscle atrophy, and activity dysfunction. If the disease is severe or prolonged, abnormal deformities may occur. In addition to the above causes of knee pain in adolescents, the symptoms may also be caused by other reasons, such as bone tumors, fracture dislocation, rheumatoid arthritis, etc. It is recommended to consult the doctor in a timely manner to clarify the cause of the disease, and to provide treatment according to the disease.