Pain in the crook of the right arm may be caused by acute injury, osteoarthritis of the elbow joint, rheumatoid arthritis, tennis elbow and other factors. 1. Acute injury: for example, external blows or acute strains can lead to local bone and soft tissue damage, which will lead to pain in the crook of the right arm, accompanied by swelling and restricted movement. 2. Osteoarthritis of the elbow joint: it may be related to joint degeneration, which can lead to osteoarthritis of the elbow joint, due to the presence of aseptic inflammation, which can lead to pain in the crook of the right arm, and when it is serious, it can lead to activity limitation. 3. Rheumatoid arthritis: it may be related to heredity, infection and other factors, when it invades the elbow joint, it will lead to pain in the bend of the right arm, which may be accompanied by swelling and morning stiffness, and in severe cases, the joint will become deformed. 4. Tennis elbow: for example, repeated twisting of the arm may lead to overuse of the forearm muscles, easy to cause tennis elbow, which will lead to pain in the crook of the right arm, in excessive activities, the symptoms of pain can be significantly aggravated, and when serious, it will affect the daily work. Pain in the crook of the right arm, lasting for a long time or accompanied by other abnormal manifestations, there may be abnormalities, it is recommended to consult a doctor for examination and treatment.