Of the 206 bones in your body, three of them are in your arm: the humerus, radius, and ulna. Your arms are also made up of muscles, joints, tendons, and other connective tissue. Injuries to any of these parts of the arm can occur during sports, a fall, or an accident.
Types of arm injuries include
You may also have problems or injure specific parts of your arm, such as your hand, wrist, elbow, or shoulder.
Your bones help you move, give you shape and support your body. They are living tissues that rebuild constantly throughout your life. During childhood and your teens, your body adds new bone faster than it removes old bone. After about age 20, you can lose bone faster than you make bone. To have strong bones when you are young, and to prevent bone loss when you are older, you need to get enough calcium, vitamin D, and exercise. You should also avoid smoking and drinking too much alcohol.
Bone diseases can make bones easy to break. Different kinds of bone problems include
NIH: National Institute of Arthritis and Musculoskeletal and Skin Diseases