March 2024 Chiropractic Newsletter Understanding the Anatomy of Joints

The adult human body is made up of 206 bones, which perform like a structural scaffolding that helps support the body to move (or ambulate). And except for one neck bone (the hyoid bone), the rest of the bones connect to at least one additional bone. The junction/point where two bones lie adjacent to each other (whether they can move or not) is called a joint.

Most joints allow for and facilitate movement (i.e., locomotion) between the bones in your body. Ironically, the community of professionals often disagree on the exact number of joints in the human body based on a debatable definition. For the sake of this discussion, adults have around 350 joints.

What Does a Joint Consist of?

A joint has these components -

• Cartilage – refers to the tissue that covers the bone surface where the bone meets the joint and helps reduce friction in the joint. Additionally, the meniscus is the cartilage in the knees and other joints that is curved
• Ligaments – the strong elastic connective bands of tissue that connect bones offer support and limit a joint's movement.
• Tendons – Tendons attach muscles to bones. They are located on each side of a joint and are responsible for the movement of the joint.
• Bursa – Fluid-filled sacs located between bones, ligaments, etc., that cushion the friction in the joint.

What are the Different Types of Joints?

The human body’s joints are classified based on the joint’s range of motion and by the tissue that holds the nearby bones together (i.e., the joint’s histological basis). Healthcare and medical professionals classify joints into three primary categories –

• Fibrous Joints – these are very inflexible joints – examples include skull plates, etc.
• Cartilaginous Joints - have some but limited movement; examples include the breastbone, etc.
• Synovial Joints – have the most movement and are where one bone fits snugly into the cavity of another bone. These types of joints typically have a membrane that seals the joint capsule and provides a fluid to lubricate the joint to add cushioning against the friction created by movement.

There are six types of synovial joints in the human body -

• Hinge Joints

A hinge joint, as its name implies, can open and close in only one direction – for example – your elbows or knees.

• Ball and Socket Joints

In this type of synovial joint, one bone with a rounded end fits into the indentation of another nearby bone. A ball and socket joint is quite versatile as it can rotate and turn in almost any direction. Some examples are your hips or shoulders.

• Condyloid Joints

Condyloid joints, similar to ball and socket joints with some rotation limitations, consist of two oval-shaped bones that fit together – examples include your wrist, toes, etc.

• Saddle Joints

Saddle joints, which allow for movement in any direction but can’t rotate or twist, are formed when two curved bones meet- an example is where your thumb meets your hand.

• Pivot Joints

Pivot joints allow for rotation without adjusting from their original position – an example is a pivot neck joint that lets you move from one side to the other.

• Planar Joints

Planar joints are formed when two mostly flat bones meet and move when one bone slides over the other – examples include the spine’s vertebrae and the wrist’s carpal bones.

Common Joint Issue Symptoms

The symptoms of a joint condition that a chiropractor can treat will vary but may include one or more of the following -

• Inflammation or swelling.
• Redness/discoloration on or near the joint.
• Warmth or heat is generated from the area.
• A grinding feeling/popping noise within the joint.

You use your joints whenever you do anything, from walking the dog to reading this article. If joint pain disrupts your life, contact a chiropractor near you today.