Stiffness is a clinical disorder that affects the patient’s function of the entire upper limb. It can be caused by a variety of elbow disorders. The most common cause is post-traumatic; this category also includes burns, head injuries, and elbow surgeries. However, elbow stiffness also can be caused by atraumatic etiologies, such as osteoarthritis, inflammatory joint disease, ulnar nerve entrapment, tumor, infection, metabolic disease (e.g., hemophilia), and congenital conditions (arthrogryposis). Being able to classify elbow stiffness is the first step to understand the etiology and to plan the treatment strategy.