Mulberry Whale PTM

A joint that can be moved out of place on demand raises an obvious question: what is happening in the tissues, and what is happening in the person?

The answer involves both. Looking only at the capsule and ligaments misses much of the picture, and looking only at behavior misses the rest.

Two patterns of shoulder instability

Clinical classifications of shoulder instability generally turn on whether the person controls the event.

Involuntary instability describes a shoulder that dislocates or subluxates spontaneously, because the joint is too unstable for the person to prevent it.

Voluntary instability describes a person who deliberately uses muscle activity to displace the joint. It is usually associated with congenital laxity or hypermobility. It also appears to develop over time in many people: the shoulder first slips involuntarily, and the person gradually learns a motor strategy that reproduces and reverses it. [1] In other words, the pattern can be learned, and a learned pattern is open to change.

A subgroup of voluntary subluxators has psychological or attention-related factors, and these cases are more difficult to manage. [1] It would be a mistake to generalize from this subgroup to everyone who can displace a joint.

Why the absence of pain is not reassurance

Lax joints often move without pain. Pain is not a direct measure of tissue state. It is an output the nervous system produces when it judges that protection is warranted, and a joint that slides freely without apparent consequence gives that system little reason to produce it. With no signal, there is no prompt to stop, and the movement is repeated.

Context shapes what repeats. Hypermobile people are well represented in dance and similar movement disciplines, [2] where extreme range is often noticed and valued. If the people around them can’t distinguish flexibility from instability, an unstable pattern may be rewarded instead of questioned.

Many people with hypermobility spectrum disorders or hypermobile Ehlers-Danlos syndrome wait years for a diagnosis. [3] In the meantime, someone may keep training or performing in ways that rely on extreme range, unaware that their joints need a different approach.

What the evidence supports

Surgery tends to give poor results when habitual subluxation is the problem, so rehabilitation is usually the starting point. Three themes recur:

• Proprioception. Joint position sense is often reduced in people with hypermobility, [4] and exercise aimed at improving it can improve both proprioception and symptoms. [5]
• Stability rather than range. Progressive exercise that develops muscular control through the shoulder’s range has a long record in the management of unstable shoulders. [6]
• Education. Helping people understand what their joint is doing, why repeated subluxation is not benign, and how to protect it is part of rehabilitation.

Limitations and what we still need to learn

This area is less settled than it may look, and several of the ideas above are reasoned inferences, not proven findings.

• Movement settings and reinforcement. No study has shown that dance or movement classes cause or reinforce voluntary subluxation. The evidence shows that hypermobile people are common in these settings, not that the settings shape the behavior.
• Continued activity. Whether people with undiagnosed hypermobility spectrum disorder or hEDS do worse when they keep training in extreme ranges has not been directly studied. It is plausible, but untested.
• Diagnostic delay. Figures on time to diagnosis come mainly from patient surveys and registries, which are open to recall bias and vary by country and health system.
• Rehabilitation evidence. Much of the work on proprioception training in hypermobility has studied small groups and joints other than the shoulder, such as the knee. [5] Trials of motor-control rehabilitation specifically for voluntary shoulder instability are limited.
• The psychological subgroup. Findings about attention-related factors come largely from older clinical studies. They should not be used to assume motives in any individual.

Useful next steps would include long-term follow-up of hypermobile people in movement disciplines, trials of rehabilitation aimed at learned subluxation patterns, and studies of whether screening for instability in movement settings changes outcomes.

Summary

• A joint that can be displaced on demand indicates laxity, not exceptional flexibility.
• Absence of pain does not mean absence of risk.
• Control is a more useful goal than range.
• Recurrent slipping, pain, or injury warrants assessment by a clinician experienced with hypermobility.

This article is general education, not medical advice.

References

1. Gerber C, Nyffeler RW. Classification of glenohumeral joint instability. Clin Orthop Relat Res. 2002;400:65-76.
2. McCormack M, et al. Joint laxity and benign joint hypermobility syndrome in ballet dancers. J Rheumatol.2004;31:173-178.
3. Wang YT, et al. Patient experiences of receiving a diagnosis of hypermobile Ehlers-Danlos syndrome. Am J Med Genet A. 2024;194(8):e63613.
4. Smith TO, et al. Reduced joint proprioception in benign joint hypermobility syndrome: systematic review. Rheumatol Int. 2013;33:2709-2716.
5. Ferrell WR, et al. Enhancing proprioception in joint hypermobility syndrome. Arthritis Rheum. 2004;50:3323-3328.
6. Burkhead WZ, Rockwood CA. Exercise program for shoulder instability. J Bone Joint Surg Am. 1992;74:890-896.