Hypermobility: Understanding Its Causes, Implications, and Management

Why is hypermobile?

Hypermobility, often characterized by an extreme range of motion in joints, primarily stems from inherent variations in the composition and structure of connective tissues, particularly collagen and elastin, which are largely determined by genetics.

Understanding Joint Hypermobility

Joint hypermobility refers to the ability of a joint to move beyond its typical, expected anatomical range of motion. While often confused with general flexibility, hypermobility is a distinct characteristic. Flexibility is the ability of muscles and tendons to lengthen, allowing a joint to move through its full range, whereas hypermobility indicates an inherent laxity in the connective tissues that stabilize the joint itself. This distinction is crucial, as true hypermobility is less about "stretching" and more about the structural integrity of the joint's supporting elements.

The Primary Culprit: Connective Tissue

The fundamental reason for hypermobility lies within the body's connective tissues, which provide structure, support, and elasticity to various organs and systems, including joints.

• Collagen and Elastin: These are the two primary proteins responsible for the strength and elasticity of connective tissues, such as ligaments, tendons, and joint capsules.

  • Collagen provides tensile strength, resisting stretching. In hypermobile individuals, the collagen fibers may be more elastic, less robust, or arranged differently, leading to less structural integrity.
  • Elastin provides elasticity, allowing tissues to stretch and return to their original shape. A higher proportion or altered quality of elastin can contribute to increased joint laxity. When the balance or quality of these proteins is altered, the ligaments and joint capsules become more extensible, permitting greater joint movement than typically observed.

• Genetic Predisposition: The production and structure of collagen and elastin are genetically encoded. Variations in genes responsible for these proteins can lead to inherited differences in connective tissue properties, making hypermobility a highly hereditary trait. If one or both parents are hypermobile, there is a significantly increased likelihood of their offspring also exhibiting hypermobility.

Anatomical and Physiological Factors

Beyond the primary role of connective tissue, other anatomical and physiological elements also contribute to or influence joint hypermobility.

• Joint Capsule and Ligament Structure: These structures are the primary stabilizers of a joint. In hypermobile individuals, the joint capsules may be inherently looser or larger, and the ligaments may be longer, thinner, or more elastic than average, offering less resistance to movement.
• Bone Shape and Joint Congruity: The way bones fit together at a joint (their congruity) also plays a role.
  • Shallow Sockets: Joints with shallower sockets (e.g., shoulder, hip) or flatter articulating surfaces offer less bony congruence, relying more heavily on soft tissue for stability. If these soft tissues are lax, hypermobility is more pronounced.
  • Bone Length/Shape: Minor variations in bone length or shape can also influence the available range of motion.
• Muscle Tone and Strength: While not a direct cause of hypermobility, muscle tone and surrounding muscle strength significantly impact joint stability in hypermobile individuals. Weaker or less responsive muscles may fail to adequately brace an already lax joint, increasing the risk of instability or injury. Strong, well-coordinated muscles can provide dynamic stability, compensating for inherent ligamentous laxity.
• Proprioception: Some research suggests that individuals with hypermobility may have altered proprioception (the body's sense of joint position and movement). This reduced joint awareness can contribute to instability and a higher risk of sprains or subluxations, as the body may not adequately anticipate or correct for extreme joint positions.

Contributing Factors and Conditions

While genetics and connective tissue are the core reasons, hypermobility can also be associated with specific conditions or influenced by other factors.

• Genetics: As mentioned, the strong hereditary component means that hypermobility often runs in families.
• Connective Tissue Disorders (CTDs): Hypermobility is a hallmark feature of several inherited connective tissue disorders.
  • Hypermobility Spectrum Disorder (HSD): This is a diagnosis for individuals with symptomatic hypermobility that does not meet the full criteria for a specific genetic CTD like Ehlers-Danlos Syndrome.
  • Ehlers-Danlos Syndromes (EDS): A group of inherited disorders primarily affecting connective tissues. Hypermobile EDS (hEDS) is the most common type and is characterized by generalized joint hypermobility, along with other systemic manifestations. Other types of EDS (e.g., classical, vascular) can also feature hypermobility.
  • Marfan Syndrome: Another genetic disorder affecting connective tissue, often leading to tall stature, long limbs, and joint hypermobility, particularly in the fingers and toes.
  • Osteogenesis Imperfecta: Primarily characterized by brittle bones, but can also involve joint hypermobility due to collagen defects.
• Hormonal Influences:
  • Relaxin: This hormone, particularly elevated during pregnancy, increases the laxity of ligaments and connective tissues throughout the body to prepare for childbirth. This effect can temporarily increase joint mobility in pregnant individuals.
  • Puberty: Hormonal changes during puberty, particularly in females, are sometimes associated with a temporary increase in joint laxity.
• Acquired Hypermobility: While less common for generalized hypermobility, localized hypermobility can be acquired through:
  • Repetitive Stretching or Training: Activities like gymnastics, ballet, or contortion, which involve extensive and repetitive stretching, can lead to increased localized joint range of motion, though this is often distinct from constitutional hypermobility.
  • Injury: Severe ligamentous sprains or ruptures can lead to permanent joint laxity in the affected joint.

Implications of Hypermobility

While sometimes advantageous in specific activities requiring extreme ranges of motion (e.g., dance, gymnastics), hypermobility can also pose challenges.

• Benefits: Enhanced flexibility can be an asset in certain sports or artistic pursuits.
• Challenges:
  • Joint Instability: Increased risk of sprains, dislocations, and subluxations (partial dislocations).
  • Chronic Pain: Due to increased stress on joints, muscles working harder to provide stability, or repetitive microtrauma.
  • Proprioceptive Deficits: Reduced awareness of joint position can lead to awkward movements or falls.
  • Fatigue: Muscles may work harder to stabilize joints, leading to increased energy expenditure.

Managing Hypermobility: A Kinesiological Approach

For individuals with hypermobility, the focus of exercise and rehabilitation shifts from increasing flexibility to enhancing joint stability and muscular control.

• Prioritize Stability Over Flexibility: Unlike general fitness recommendations, hypermobile individuals should generally avoid deep stretching that pushes beyond their comfortable range, as this can exacerbate laxity.
• Strength Training:
  • Focus on Eccentric and Isometric Control: Emphasize slow, controlled movements and holding positions to build strength through the full range and at end-ranges.
  • Compound Movements with Good Form: Strengthen the muscles surrounding the joint to provide dynamic stability.
  • Targeted Strengthening: Address specific muscle groups that contribute to joint stability (e.g., rotator cuff for shoulders, glutes and core for hips).
• Proprioceptive Training: Exercises that challenge balance and joint position sense (e.g., single-leg stands, wobble board exercises, unstable surfaces) can improve neural control and reduce injury risk.
• Core Stability: A strong core provides a stable base for all limb movements, which is particularly crucial for hypermobile individuals.
• Low-Impact Activities: Activities like swimming, cycling, or elliptical training can be beneficial for cardiovascular health without excessive joint impact.
• Professional Guidance: Consultation with a physical therapist, kinesiologist, or exercise physiologist experienced in hypermobility is highly recommended to develop a safe and effective exercise program tailored to individual needs and to address any associated symptoms.