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what is a joint and what do joints do

What Is A Joint?

What is a joint and what do they do? This is the fourth piece in our Anatomy Class series. You can go back and read the previous three on Tendons, Ligaments and Fascia. In the series we will take you through all the interesting tissues which make up our musculoskeletal system.

What Is A Joint

Well, this is an extremely broad question! Joints can be broken down into many subcategories. By definition, a joint is simply the junction of two bones within the musculoskeletal system. The most common joint classification system uses the type of movement available at the joint, and the tissues present within the structure. 

  • Fibrous joints, often found in the skull, occur when the bones are secured by a tough, fibrous tissue. 
  • Cartilaginous joints are bound by hyaline cartilage or fibrocartilage and are most commonly found between the vertebrae in our backs.
  • The most common joint we think of when working with musculoskeletal complaints are called synovial joints. The most widespread throughout our bodies, synovial joints are freely mobile and are identified by their fluid-filled joint cavities encased by an articular capsule. 

Within our synovial joint capsule, the connecting bones are lined with cartilage and surrounded by a membrane filled with synovial fluid, allowing smooth movement between the neighbouring bones.

Synovial joints can also be further split down into subcategories – this is a pretty big umbrella we’re standing under, in case you haven’t noticed!

  • Saddle – yep, like the one on a horse’s back – occurring when the adjacent bones unite with a complementary convex-concave shape, like a puzzle! Example: carpometacarpal joints in the hands.
  • Pivot – allowing for rotational movements from side to side. Example: the atlantoaxial joint of the neck.
  • Condyloid/Ellipsoid – when a small depression in one bone is united with a reciprocal rounded bone. Example: the radiocarpal joint of the wrist. 
  • Ball & Socket – these ones are the most move-y! The rounded head of one bone fits perfectly into the concave socket of the other, allowing for heaps of axial movements. Example: the glenohumeral joint (shoulder).
  • Plane/Gliding – in these joints, the surfaces of the adjacent bones are either slightly curved or completely flat, allowing the bones to glide across each other and perform multiple movements. Example: the subtalar joint below the ankle.
  • Hinge – as the name suggests these joints hinge back and forth to facilitate flexion and extension motions. Example: the metatarsophalangeal joints of the feet.  

What Do Joints Do?

Joints form the union between two bones and are pivotal (pun intended!) for movement, stability and structure.

Why Are Joints Important?

To put it simply, we wouldn’t be able to comfortably move without joints. If we had solid boned feet with no joints we couldn’t adapt to different surfaces, adjust for balance and spring off like the majestic athletes we all are. We wouldn’t be much good at all without our joints to move, structurally support, stabilise and enable. 

How Do We Treat An Injured Joint?

Sometimes due to the unique ways our bodies move, the sports we play, the shoes we wear or the demands we impose, our joints can be subjected to twists and turns that they weren’t expecting! 

This can be the beginnings of an array of different inflammatory responses within the joint. As mentioned above, there are a number of structures enveloped within the joint capsule. 

Capsulitis is an inflammation of said joint capsule, and synovitis is an inflammation of the synovial membrane encasing the fluid within the joint. 

People presenting to the clinic with pain in their big toe joint are often experiencing one of these injuries. 

Treatment is very subjective to the nature and severity of the injury. A simple change in footwear combined with anti-inflammatories could do the trick at alleviating big toe joint pain. For others, improvement may require a period of load optimisation in a moon boot to allow the inflammation to settle. 

You might also achieve this with decreases in exercise, footwear changes, padding, taping or the use of 3D printed custom-made foot orthotics. For those on the mend, returning to mobility and normal activity will require a tailored exercise program to strengthen the stabilising structures (ligaments, tendons, muscles etc) surrounding the joint, ensuring it is always secure and steady for optimal performance

*Side note, as I’m typing this, I’m realising how many relevant words there are that start with S, and I just feel the need to make a point of it:

  • Synovial (joint)
  • Structure
  • Stabilise
  • Secure
  • Steady
  • Strengthen

Anyone else noticing a theme? Anyway, don’t mind me getting distracted by joints! Back to the article…

In some cases where osteoarthritis is beginning to form within a joint, the cartilage that allows the bones that make up the joint slide and glide past each other can become injured. This means we may need to look into the ‘zone of optimal stress’ pertaining to that particular joint. 

See, think of it like body temperature. As I’m typing this, it’s a whopping 35 degrees outside. I don’t love the scorching heat, so for my body, anything above around 26/27 can be uncomfortable. Similarly, anything below 14/15 can have me shivering in a blanket in the foetal position. 

Just like my body temperature, our joints have a spectrum where they best like to operate! In the instance of osteoarthritis, too much movement can be painful, and too little movement may also do more harm than good! 

Our role here is to find that ‘Goldilocks’ zone, focusing on load optimisation and finding the sweet spot where the joint is at its most comfortable.

What Can I Do About My Sore Joint (s) At Home?

The foot and ankle contains soooooo many joints. There are 28 bones swimming around in there that need to be comfortably united! Identification of the injured joint is super important when guiding treatment plans. The best advice I could give as a podiatrist would be to come and see us! We can figure out why a particular joint has become aggravated and concoct your magical potion of a treatment plan. 

But, if for some reason you are unable to pop into one of our conveniently located clinics (shameless plug), your feet will be much happier in really good runners than they would be in your work heels or casual vans! 

If you think you’re experiencing foot joint pain, number 1 is to wear good shoes. Some anti-inflammatories are often useful at taking the edge off the pain, but please only take them if you have no pre-existing aversions and avoid if they’ve been forbidden by your GP. Make sure you take them with food, and cease if you experience any gastrointestinal burdens. While Nurofen/Voltaren can address the short-term pain, the contributing factors to your joint pain still need to be determined for long-term prevention!

Joint Summary

  • Joints are the thingymajigs that facilitate comfortable movement between two adjacent bones in our bodies. 
  • At a foot level, there are heaps of joints that you walk all over everyday!
  • Wear good shoes!
  • Ideally, our joints are assisted in their role by stabilising structures, but sometimes they can become angry. 
  • Identification of the injured joint is vital in facilitating a treatment plan to optimise joint function.
  • Wear good shoes!
  • Pop in and see us if you think you have an angry joint!

…And one more thing… wear good shoes 🙂

From The Author

I hope you’ve found this post a useful introduction to the joints in our bodies, particularly the foot and ankle. If you’ve found this helpful and know someone else who has struggled with joint problems please share it.

But if you have pain that you suspect is related to a damaged joint then you can book in with our physiotherapists (for your above the knee problems) or our podiatrists (for your below the knee problems).

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