The term double-jointed is an inaccurate way of saying that someone has hypermobility of their joints. Double-jointed would imply that the individual has more joints than normal or that their joints have a twice-normal motion – neither of these is true. The truth is that people who are called "double-jointed" have joints with more mobility than normal. In some individuals, this is normal. In others, there is an underlying medical reason for the joint laxity. For example, people with Ehlers-Danlos syndrome have abnormal connective tissue, allowing for excessive joint motion.1
Joint hypermobility is defined as "abnormally increased mobility of small and large joints beyond the limits of their physiological movement." It is common in young females and usually tends to lessen with age.1 Hypermobility is seen in about 5% of the healthy adult population. People of Asian and Afro-Caribbean descent are more likely to have hypermobility. People from the Indian subcontinent have more supple hands than people of European ancestry.
Some people can train their joints to have more mobility, and this is often a focus of sports and activities that require great flexibility. For example, ballet dancers and gymnastics often increase their joint mobility by focused and continued efforts to stretch the ligaments and connective tissue around the joint. For most people, this increase in joint mobility does not have any medical symptoms.
On the other hand, people with true joint hypermobility are born with genetic differences in the makeup of their collagen that allows for the laxity of joints, without ever having to try to stretch the tissues.2
Understanding the Function of Human Joints
The factors that can contribute to having hypermobile joints include:
You may have abnormal collagen or elastin fibers due to an inherited trait.1
As these fibers make up the ligaments that hold joints together, your joints will be looser.
The bones in your joints sockets may by unusually shallow so there can be a greater range of motion but also may be a greater risk of dislocation.
Poor muscle tone, which may be due to nervous system impairment, can result in abnormally relaxed muscles and more movement in your joints.
Abnormal proprioception, sensing of the position of the joint, can lead to overextending it without feeling you are doing so.
People with Down syndrome, Marfan syndrome, osteogenesis imperfecta, and Ehlers-Danlos syndrome often have joint hypermobility.2
Training and exercise, such as yoga and athletic training, can increase your range of motion and joint mobility.
How Your PT Measures Your Strength
Joint Hypermobility Syndromes
When your joint hypermobility leads to pain or increased injuries, it rises to a classification of a joint hypermobility syndrome. Symptoms may include joint pain and stiffness, clicking, dislocation, fatigue, and recurrent sprains.3
A visit to your doctor can lead to a diagnosis. One tool they use is scoring the movements of your thumb, wrist, fifth finger, elbows, lower back, and knees to produce the Beighton score and using the Brighton criteria to further assess the number of hypermobile joints, pain, dislocations, injuries, and lax skin.
Physical therapy and exercise can help strengthen and protect the joints and muscles. Analgesics can be used for pain and non-steroidal anti-inflammatory drugs for swelling.