The Anatomy of Hinge Joints

Joints form where one bone connects to another bone, allowing the skeleton to move. There are several different types of joints within the body that differ in structure and the way they move depending on where in the body they are located.

This article will discuss different types of joints, how a hinge joint moves, and examples of hinge joints throughout the body. 

Anatomy

A joint is formed by the joining of two or more bones together. The human body has three main classifications of joints that are categorized by the degree to which they can move. These include:

• Synarthroses: These are fixed, immovable joints formed by the connection of two or more bones.
• Amphiarthroses: These are slightly movable joints that allow for a very small degree of movement, also known as cartilaginous joints. The bones that form the joints are separated by a fibrocartilage disc. 
• Diarthroses: These are the most common freely moving joints that allow movement in multiple directions, also called synovial joints. The bones that form the joints are lined with articular cartilage and enclosed in a joint capsule filled with synovial fluid that allows for smooth joint motion. 

Synovial joints are further classified into different types depending on differences in joint structure and the number of planes they allow movement in. These include hinge, ball and socket, planar, pivot, saddle, and ellipsoid joints.

A hinge joint is a synovial joint that allows movement in one plane of motion similar to how a door hinge moves forward and backward. The end of one bone within the joint is typically convex, or pointed outward, vs. concave, or rounded inward, to allow the ends to fit together smoothly.

Because hinge joints only move through one plane of movement, they are generally more stable than other types of synovial joints.

Examples of hinge joints include:

• The knee joint that allows the knee to bend and extend
• The elbow joint that allows the elbow to bend and extend
• The finger and toe joints that allow the fingers and toes to bend and extend
• The talocrural joint of the ankle that allows the ankle to move up (dorsiflexion) and down (plantarflexion)

Function

Hinge joints allow for movement of the limbs, fingers, and toes to extend away and bend in toward the body. Movement of the hinge joints of the knees, shoulders, ankles, fingers, and toes are essential for all daily functions, from activities of daily living like bathing, getting dressed, and eating, to everyday movements like walking and standing up and sitting down. 

Associated Conditions

Osteoarthritis and inflammatory forms of arthritis can affect any joint. Autoimmune inflammatory forms of arthritis, including rheumatoid arthritis and psoriatic arthritis, that cause the body to attack its own joints also commonly affect the knees and fingers, resulting in swelling, stiffness, and pain.

Gout, while not an autoimmune condition, is also an inflammatory form of arthritis that develops from elevated levels of uric acid in the blood and most commonly affects the hinge joint of the big toe. 

Other conditions that affect hinge joints include injuries to the cartilage within the joints or ligaments that stabilize the outside of the joints. Ligament sprains or tears can result from jamming the fingers or toes, rolling the ankles, and twisting injuries or direct impact to the knee. These types of injuries to the knee may also cause injury to the meniscus, a C-shaped portion of tougher cartilage within the knee joint that helps cushion and absorb shock.

Rehabilitation

Conditions that affect hinge joints often cause inflammation and swelling, resulting in pain and limited joint movement. After injuries or during flare-ups of inflammatory conditions, limiting active movement and resting the affected hinge joint is beneficial at first to reduce increased stress and pain to the joint. Applying ice and using pain-relieving medications like nonsteroidal anti-inflammatory drugs (NSAIDs) can also help reduce pain.

Once your pain and swelling start to subside, physical therapy or occupational therapy can be used to help rehabilitate your affected hinge joints. Your physical or occupational therapist will provide you with stretches and exercises to help improve the range of motion of your joints and strength of surrounding muscles to support your joints. 

If you experience hinge joint pain from an autoimmune condition like rheumatoid arthritis or psoriatic arthritis, biologic medications to decrease your body’s autoimmune activity are often administered through infusions delivered every several weeks or months. Cortisone injections may also be used to decrease inflammation within your painful joints.

Summary

Hinge joints are a type of synovial joint that moves throughout one plane of motion into flexion and extension. Hinge joints are found in the knees, elbows, ankles, fingers, and toes, and control movement essential for all daily functions. Injuries, osteoarthritis, and autoimmune conditions can all affect hinge joints while rest, medication, ice, and physical therapy can help reduce pain and improve your strength and range of motion. 

A Word From Verywell

If you have difficulty fully bending or extending your fingers, toes, elbows, ankles, or knees, make sure to speak with your healthcare provider. Joint stiffness is often a sign of arthritis, and all forms of arthritis tend to worsen over time without treatment. Regular movement and exercise are key for reducing joint stiffness to keep your hinge joints moving properly to support your daily activities.