The arm cannot be straightened up, usually due to the elbow joint function limitation, its causes mainly include soft tissue adhesion, elbow joint deformity, joint dislocation, etc. The treatment is mainly functional exercise, surgical treatment, reset therapy, etc. 1. Soft tissue adhesion: mostly seen in elbow joint trauma or after surgery, early stage can be slowly recovered through functional exercise, late stage adhesion is usually more serious, may need to release the adhesion through surgery. 2. Elbow deformity: including congenital deformity and acquired deformity, which can be treated by corrective surgery. 3. Joint dislocation: mostly caused by violent blows, usually through manipulation or surgical treatment to reset the joint. When the symptom of not being able to straighten up the arm occurs, it is recommended to consult a doctor in time, after clarifying the cause of the disease, to receive appropriate treatment, so as to avoid delaying the disease.