What Makes a Joint 'Stable'?

‘Stability’ is a term thrown around by those in the Strength and Conditioning world without much context, particularly for the athlete that doesn’t have much, if any, anatomical foundation. So today’s blog is to provide the foundational knowledge needed to decipher exactly what ‘stability’ means and what influences joint stability.

To understand ‘Stability’ best we must first define 2 key terms:

Stable: not likely to give way or overturn; firmly fixed.

Mobile: able to move or be moved freely or easily.

In relation to the body and joints, we can look at ‘Stability’ and ‘Mobility’ on a continuum. At one end you have a completely fixed joint and at the other end you have a freely moving joint. In order to have a ‘stable’ joint we must move away from the ‘mobile’ end of the continuum, and vice-versa. We can not shift to one end of the continuum without reducing the effects of the other. Without delving too deep, the human body alternates from ‘stable’ joints to ‘mobile’ joints along the kinetic chain. Mike Boyle’s and Gray Cook’s Joint-by-Joint approach delves into this topic deeply, if you are interested I’d recommend looking into it.

Stability/ Mobility Continuum

Stability/ Mobility Continuum

There are 3 main factors that govern Joint Stability and Mobility:

1) Osseous Formation/ Restrictions:

  • How the bones of the joint are formed and how they articulate with each other.

For the most part, we can not alter osseous restrictions without a scalpel, drill and saw as seen in surgery. Our bone structure is genetic and has great implications on the positions/ joint ranges we have access to, particularly at the ankles, hips and shoulders.

One way of increasing osseous restrictions and hence osseous stability is through Latarjet surgery to increase glenohumeral stability in the anterior shoulder. Having hip surgery to remove bony protrusions on the acetabular lip or femoral head is a way to increase hip mobility in people with Femoral Acetabular Impingement.

Relocation of the Coracoid Process to the Anterior Inferior Glenoid through Latarjet Surgery

Relocation of the Coracoid Process to the Anterior Inferior Glenoid through Latarjet Surgery

2) Passive Restraints:

  • Ligaments

  • Labrums

  • Fascia

  • Cartlidge

  • Menisci

  • Neural and Vascular Pathways

The passive restraints have no Central Nervous Systems control, so for the most part, we do not have much effect on the Passive Restraints that influence joint stability and mobility.

Mobility can be significantly increased by damaging these passive structures. Someone who has previously rolled their ankle and damaged the key ligaments that offer passive stability to the lateral ankle will more than likely experience more ankle instability (mobility) than someone who has strong, stable ligaments without previous injury.

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As coaches, we may have small influence on fascial systems and capsular health with specific mobility training interventions. However, the overall influence is minuscule to what is possible with the 3rd factor to joint stability - Active Restraints.

Active Restraints:

  • Muscles

  • Tendons

  • the available input of the Central Nervous System.

Active restraints is where we as coaches and anyone without a scalpel for that matter, have significant influence on the stability AND mobility of the human body as a whole.

We can increase joint stability by strengthening muscles, improving coordination and sequencing of muscle timing through compound movements. We can increase stability by improving proprioception and reactive muscle timing at the rotator cuff and the deep ankle stabilisers to better handle uncontrolled perturbations to the joints from different sporting endeavours.

Mobility can be increased at specific joints by reducing neural tone to ‘tight’ muscles, and by exposing ‘short’ muscles to stretching protocols and new ranges through eccentric loading and isometrics. We can also increasing the mobility of adjacent joints by strengthening key muscles of supporting/ proximal joints. This is often seen when the core is strengthened allowing for more mobile hips and shoulders.

For the most part, joint stability can only really be influenced by coaches and rehab professionals through ‘Active Restraints’ - the muscles and tendons that create movement of the skeletal system and the central nervous systems that allows this movement to occur. All other forms of ‘stability’ training are just strength training in disguise.

About the Author
Jamie Smith, Owner and Director of Coaching at Melbourne Strength Culture
IG: @j.smith.culture
YouTube: Melbourne Strength Culture

Email: jsmith@melbournestrengthculture.com