Medical professionals report that the term "double-jointed" is a layman's description for joint hypermobility, a condition where joints move beyond the typical range of motion. Dr. Maryellen Brucato, a board-certified foot and ankle surgeon, stated that individuals do not possess extra joints, but rather have skeletal frameworks where joints stretch and move beyond a typical baseline. This mobility is attributed to differences in connective tissues, such as ligaments and collagen fibers, that support the joints.
According to Dr. Nicholas Belasco, a sports medicine physician, hypermobility affects between one in 10 and one in three people, depending on the criteria used. Medical providers often utilize the Beighton score, a nine-point test, to assess hypermobility by checking if a person can bend their pinky past 90 degrees, touch their thumb to their forearm, or place their palms flat on the floor without bending their knees. While many children exhibit hypermobility—roughly two-thirds of those aged 4 to 7—the prevalence often decreases to about 1 in 10 by the early teens.
The condition is frequently linked to genetics and inherited disorders that affect collagen production, such as Ehlers-Danlos syndrome (EDS). Dr. Jacques Courseault of the Tulane University School of Medicine noted that research is also investigating the role of folate metabolism and MTHFR gene variants in connective tissue biology. Beyond flexibility, hypermobility can be associated with other symptoms, including chronic joint pain, frequent sprains, easy bruising, and conditions like postural orthostatic tachycardia syndrome (POTS) or mast cell activation syndrome (MCAS).
For the millions of people with hypermobility spectrum disorders, the day-to-day impact involves muscles working harder to compensate for loose joints, which can result in chronic fatigue, muscle tension, and a diminished sense of joint position, known as proprioception. Those with systemic conditions like EDS may also notice skin changes, such as velvety or unusually stretchy skin, alongside gastrointestinal issues or dizziness when standing. According to Dr. Belasco, patients often face a significant delay in management, waiting an average of 10 years or more for a formal diagnosis.
The medical community advises that if flexibility is accompanied by pain lasting several months or joints slipping out of place without injury, individuals should seek a specialist's evaluation. Management typically includes gradual strength and balance training to stabilize the joints. In some cases, such as hypermobile feet, patients may need custom orthotics to limit excessive motion and prevent long-term joint damage. Early identification is emphasized to help patients understand the maintenance required for their specific connective tissue type and to address potential knock-on effects across multiple organ systems.