Hypermobility Spectrum Disorder (HSD): Prevalence, Diagnostic Challenges, and Management

How many people have HSD?

Quantifying the exact prevalence of Hypermobility Spectrum Disorder (HSD) is challenging due to evolving diagnostic criteria, underdiagnosis, and its broad clinical presentation. While general joint hypermobility is common, HSD, which encompasses symptomatic hypermobility, is estimated to affect a significant, though not precisely defined, portion of the global population, likely ranging from 1% to 5% or more depending on the population studied and diagnostic methodology.

Understanding Hypermobility Spectrum Disorder (HSD)

Hypermobility Spectrum Disorder (HSD) refers to a group of conditions characterized by symptomatic joint hypermobility that does not meet the criteria for a specific heritable disorder of connective tissue, such as hypermobile Ehlers-Danlos Syndrome (hEDS). It represents a spectrum of clinical presentations, from localized joint hypermobility (LJH) affecting a single joint or area, to generalized joint hypermobility (GJH) affecting multiple joints, often with associated chronic pain, fatigue, and other systemic manifestations.

It's crucial to distinguish HSD from benign joint hypermobility. Many individuals possess flexible joints without experiencing any adverse symptoms; this is simply a variation of normal physiology. HSD, however, implies that the hypermobility is causing problems, such as pain, dislocations, subluxations, proprioceptive deficits, or other systemic issues. The diagnosis of HSD is made clinically, primarily by a medical professional experienced in hypermobility, after excluding other conditions.

The Challenge of Quantifying HSD Prevalence

Determining precise prevalence figures for HSD is complex for several reasons:

• Evolving Diagnostic Criteria: The understanding and classification of hypermobility-related disorders have evolved significantly. The 2017 International Classification for Ehlers-Danlos Syndromes and Related Disorders, which introduced HSD as a distinct category, helped clarify diagnosis but also means older prevalence studies may not directly apply.
• Lack of a Definitive Test: Unlike some conditions, there is no blood test, genetic marker, or imaging study that definitively diagnoses HSD. Diagnosis relies on a comprehensive clinical assessment, including a physical examination, medical history, and exclusion of other conditions.
• Underdiagnosis and Misdiagnosis: Many individuals with HSD, particularly those with less severe symptoms or those whose symptoms are attributed to other causes (e.g., "growing pains," "fibromyalgia"), remain undiagnosed or misdiagnosed. Lack of awareness among healthcare professionals is a significant contributing factor.
• Spectrum of Severity: HSD encompasses a wide range of symptoms and severities, making it difficult to capture all affected individuals under a single prevalence statistic. Some individuals may only have mild, localized issues, while others experience widespread pain and systemic complications.
• Population Variability: Prevalence can vary significantly across different populations (e.g., children vs. adults, specific ethnic groups, athletes vs. sedentary individuals).

Estimated Prevalence Rates

Given the challenges, exact figures for HSD prevalence are difficult to pinpoint. However, we can draw some conclusions:

• General Joint Hypermobility (GJH): This is relatively common. Studies suggest that 10-20% of the general population may exhibit GJH, with higher rates observed in children, adolescents, and females. It is important to reiterate that GJH does not automatically equate to HSD; most individuals with GJH are asymptomatic.
• Hypermobility Spectrum Disorder (HSD): While less common than GJH, HSD is considered more prevalent than hypermobile Ehlers-Danlos Syndrome (hEDS), which is estimated to affect approximately 1 in 5,000 to 1 in 20,000 people. Some clinical estimates suggest that HSD could affect 1% to 5% or more of the general population, though robust epidemiological studies are still emerging. This range is an approximation based on clinical observations and regional studies, rather than a definitive global survey.
• Clinical vs. Population Studies: Prevalence estimates often differ between studies conducted in specialized clinics (which naturally see a higher concentration of symptomatic individuals) and broader population-based surveys.

Who is More Likely to Be Affected?

Several factors are commonly associated with a higher likelihood of HSD:

• Sex: Females are generally more affected than males, both in terms of generalized joint hypermobility and the development of symptomatic HSD.
• Age: Joint hypermobility tends to decrease with age, so HSD symptoms often manifest in childhood, adolescence, or early adulthood.
• Genetics: There is a clear familial predisposition to hypermobility, suggesting a genetic component, although the specific genes involved in HSD are not yet fully understood.
• Ethnicity: Some studies suggest variations in hypermobility rates across different ethnic groups, though more research is needed to understand its implications for HSD prevalence.

Impact and Importance of Diagnosis

Despite the difficulty in quantifying its exact prevalence, the number of individuals living with HSD is substantial. The impact of undiagnosed or mismanaged HSD can be significant, leading to:

• Chronic Pain: Often widespread and debilitating, impacting daily activities and quality of life.
• Recurrent Injuries: Frequent sprains, strains, dislocations, and subluxations due to joint instability.
• Fatigue: A common and often debilitating symptom, not fully explained by activity levels.
• Proprioceptive Deficits: Reduced awareness of body position in space, increasing injury risk and contributing to clumsiness.
• Associated Conditions: HSD often co-occurs with conditions like dysautonomia (e.g., POTS), gastrointestinal issues, anxiety, and mast cell activation syndrome, further complicating diagnosis and management.

Accurate diagnosis is crucial for appropriate management, which can significantly improve quality of life and prevent long-term complications.

Living with HSD: A Kinesiology Perspective

From an exercise science and kinesiology perspective, managing HSD involves a strategic, individualized approach focused on stability, strength, and proprioception, rather than flexibility.

• Prioritize Stability over Flexibility: While hypermobile, individuals with HSD often lack joint stability. The goal is to build strength around the joints to provide active support.
• Proprioceptive Training: Exercises that enhance body awareness and joint position sense (e.g., balance exercises, single-leg stands, unstable surface training) are vital to improve motor control and reduce injury risk.
• Strength Training: Focus on building muscle strength, particularly in the core and around hypermobile joints. Exercises should emphasize controlled, slow movements through a pain-free range of motion, avoiding end-range stretching. Eccentric muscle contractions (the lengthening phase of a movement) can be particularly beneficial for building stability.
• Low-Impact Activities: Activities like swimming, cycling, and elliptical training are often well-tolerated as they minimize impact on joints.
• Avoid Overstretching: Individuals with HSD should generally avoid static stretching and practices that emphasize extreme flexibility, as this can exacerbate instability and pain. Dynamic movement within a safe, controlled range is preferred.
• Pacing and Energy Conservation: Many individuals with HSD experience significant fatigue. Learning to pace activities and conserve energy is critical for sustainable engagement in exercise and daily life.
• Individualized Programming: A "one-size-fits-all" approach is ineffective. A qualified fitness professional or physical therapist with experience in hypermobility can design a safe and effective exercise program tailored to individual symptoms and joint involvement.

Conclusion

While precise figures remain elusive due to its multifaceted nature and evolving diagnostic criteria, Hypermobility Spectrum Disorder (HSD) affects a considerable number of people globally. Its prevalence is likely significantly higher than previously recognized, underscoring the need for increased awareness among both the public and healthcare professionals. Early and accurate diagnosis, coupled with a comprehensive, kinesiologically informed management strategy, is paramount to mitigating symptoms, improving joint stability, and enhancing the overall quality of life for individuals living with HSD.