Voluntary joint dislocation
Also called: Voluntary subluxation · Popping joints out
Pushing a joint partly or fully out of its socket on purpose, then back in. Between 10% and 25% of people have some joint hypermobility. One survey of students and their siblings found 0.5% to 2.6% could dislocate a shoulder at will.
How common
Can you do this?
How it works
A joint is held together by its shape, by a capsule of tough tissue around it, by ligaments, and by the muscles that cross it. A subluxation is a partial slip, where the bone surfaces lose some contact. A dislocation is a full separation3. In most people both need force from outside, such as a fall.
Some people can do it on purpose. The shoulder is the usual joint, because its socket is shallow. The person relaxes the muscles around the joint, pushes it in the loose direction, and lets it slip. It goes back with a pull or a shrug.
Loose ligaments help. In the shoulder, the trick depends mostly on unusual muscle control5. Joint hypermobility, where joints bend further than average, is common1. Voluntary dislocation is much rarer. Loose joints from a connective tissue disorder, such as one of the Ehlers-Danlos syndromes, make dislocation easier2. In these inherited conditions the collagen that gives ligaments their strength is weaker or more elastic than normal2.
How common it is
One online survey asked German medical students and their siblings about this5. Between 0.5% and 2.6% could dislocate a shoulder at will5. No study has counted it for other joints. For all joints together, the nearest solid number covers a much broader trait. Between 10% and 25% of people have hypermobile joints1. Only a small share of people can dislocate a joint at will, and not all of them have loose joints in general5. A larger survey that covers other joints would give a better figure.
Is it a problem?
Popping a joint out is not an emergency if it goes back easily and does not hurt. It is still not free. Each slip stretches the ligaments a little more and can scrape cartilage. Over time this can make the joint slip out more easily3. Nerves and blood vessels run close to most joints and can be pinched.
See a doctor if:
- a joint slips out often,
- the joint hurts,
- the joint will not go back,
- your joints are loose all over.
A doctor can check for hypermobility and for Ehlers-Danlos syndrome, and can suggest ways to keep the joint stable1. Doing it for an audience is a poor trade.
History and culture
In the 1989 film Lethal Weapon 2, the character Martin Riggs escapes a straitjacket by dislocating his own shoulder4. It is not a good example to copy.
Sources and further material
- Wikipedia Hypermobility (joints) Gives the 10% to 25% prevalence of hypermobile joints and its links to connective tissue disorders.
- Wikipedia Ehlers–Danlos syndromes Inherited collagen disorders that can cause frequent subluxations and dislocations.
- en.wikiquote.org Lethal Weapon 2 (Wikiquote) The 1989 film in which Riggs frees himself from a straitjacket by dislocating his shoulder.
- NCBI Epidemiology of functional shoulder instability: an online survey BMC Musculoskeletal Disorders. Of 1,236 medical students and siblings who answered, 32 could dislocate a shoulder at will, a prevalence of 0.5% to 2.6%. Only 41% of them reported general hyperlaxity.
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Related oddities
Joint hypermobility
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