A person who is affected by an injury or some health condition may become inactive. Total inactivity may lead to decrease in a person's muscle strength and flexibility, which may over time result in dysfunction or even locking of the joints. Thus, range of motion exercises have been designed to avoid such problems. However, we first need to know what is meant by range of motion. Range of motion (or ROM) is a measure of the movement at each joint. It is also referred to as a joint's capacity of moving from full flexion to full extension. The primary purpose of range of motion exercises is to maintain the strength, flexibility, and mobility of specific joints. Furthermore, they help reduce stiffness, swelling, pain, and help improve one's range of motion. These exercises mainly involve stretching the muscles and moving the joints. ROM exercises are of two types. When a person is able to do the exercises without any assistance, they may be referred to as active range of motion exercises (AROM). In this case, the person has the muscle strength for the movement of joints or to perform the exercise by himself/herself. Whereas, there are some exercises wherein a person needs assistance as he/she has less muscle strength, and these can be referred to as passive range of motion (PROM) exercises. In this case, the person need not put any effort as someone like a caregiver will help him do the joint exercises. The other type of range of motion exercises is active assistive (or AAROM). Here, the individual uses the muscles surrounding the joint, but also requires the help of a therapist or a device to do the same. Here, we give you the differences between AROM and PROM exercises. The type of ROM exercise that is most beneficial for a person, would be best decided by a therapist. Sometimes, AROM and PROM may be used together. This happens when a person has a certain pair of joints that is strong while another pair of joints that is weak. In this case, AROM exercises may be recommended for the strong joints and PROM exercises for the weaker ones. Whether a person needs to perform AROM exercises or PROM exercises would also depend on some other factors. For example, a person who is disabled or bedridden due to an injury or illness would be recommended the passive range of motion exercises. On the other hand, a person who is able to move on his own can improve joint function, flexibility, and build muscles, by performing active range of motion exercises. ROM exercises need to be stopped immediately if you experience any kind of pain. Moreover, it is always better to consult your physical therapist to confirm whether the exercise is being performed correctly or the pain is due to some other reason.