Saddle Joint: Definitions, Examples, Origin, Features, Movement, Functions, Structure, and Associated Problems

Saddle Joint Overview

One of the three types of joints in the body are synovial joint. Because they have a fibrous joint capsule filled with synovial fluid, synovial joints are special. Synovial joints come in the form of hinge and ball-and-socket joints. Another variety of synovial joints is saddle joints.

What is a Joint?

A joint is often defined as a location where two or more objects are joined. It is the location where two bones meet in this instance. A joint is an articulation, or, to put it another way, a solid link holding the teeth, cartilage, and bones together. It is required for all bone-related movements in the body. Movement is accomplished through a variety of joints using the force produced by muscles. Numerous diverse elements affect how easily and to what extent particular joints may move. They could be categorized according to two separate criteria.

What is a Saddle Joint?

A saddle joint, also known as a sellar joint, enables several motions in numerous directions. One concave bone shaped like a saddle, and another convex bone, fashioned like a rider perched on a horse's saddle, make up a saddle joint. A saddle joint's construction aids in maintaining its stability and lessens the possibility of damage from repeated use. Your body only has a few saddle joints. These joints may be found in the inner ear, the thumb, and the shoulder.

Examples of Saddle Joint

The following are some of the examples of a saddle joint-

Incudomalleolar Joint

This joint joins the malleus and incus, two little bones that are found in the inner ear. Your hearing depends on both of them. The primary role of the incudomalleolar joint is to aid in the transfer of vibrations in your ear that your brain interprets as sounds. Injuries to the head, ongoing ear infections, and improperly inserted foreign objects can all harm this joint and impair your hearing.

Sternoclavicular Joint

The manubrium, which is the top of your sternum (breastbone), joins your clavicle (collarbone) at this junction. Along with other motions, it supports your shoulder and enables you to raise your arm above your head. The sternoclavicular joint is surrounded by some of your body's strongest ligaments, making it difficult to be hurt. However, your sternoclavicular joint might be harmed by high-impact collisions, falls, or automobile accidents.

Trapeziometacarpal Joint

The trapeziometacarpal joint at the base of your thumb is the best illustration of a saddle joint. It joins your thumb's metacarpal bone and trapezium. Your thumb may stretch out widely to help you grab huge things thanks to the flexion-extension and abduction-adduction properties of this joint. It can also slide inside to snugly contact each of your other fingers. Osteoarthritis can also affect your thumb and inner wrist at this location, resulting in discomfort, weakness, and stiffness.

Origin of Saddle Joint

The interplay of the concave and convex bone surfaces is referred to as a "saddle" because both bone surfaces resemble a saddle on a horse. The sellar joint is another name for the saddle joint.

Features of Saddle Joint

The following are some of the features of the saddle joint-

1. Condyloid joints and saddle joints have similarities.
2. In comparison to other forms of synovial joints, saddle joints are more flexible and interlocking.
3. Saddle joints don't offer a full rotation as ball and socket joints do.
4. Saddle joints have a construction that combines a ball and socket joint with a hinge joint.
5. The connecting bones have a saddle-like form that fits together.
6. The range of mobility at this joint is larger than at other joints.
7. The saddle joint gets its name from its construction or form.
8. The saddle joint got its name because it resembles a saddle seat quite a bit.

Location of Saddle Joint 

The human body has three saddle joints. The following places where you may locate them are as follows-

1. Base of the thumb: Your thumb's base has a saddle-shaped joint. At the base of your thumb, between the trapezium and the first metacarpal bone, lies a joint known as the first carpometacarpal joint.
2. Ear: Your inner ear contains a saddle-shaped joint called the incudomalleolar joint. It is located in your ear between the malleus (hammer) and the incus (anvil). The functions of hearing and understanding sounds depend on these two tiny bones.
3. Shoulder: The sternoclavicular joint is the saddle joint in your shoulder. The only joint that joins your arm to your body is one of the four joints that make up the shoulder. This joint is found at the base of your neck, where your sternum, or breastbone, joins your clavicle, or collarbone. 

Movement in Saddle Joint

Saddle joints, in contrast to hinge joints like the ones between the bones in your fingers, offer a considerably wider range of motion than a simple backward and forward movement. The primary movements of saddle joints are flexion-extension and abduction-adduction. Although flexion and extension are opposing motions, they are simple to picture. The angle between the upper arm and forearm is reduced as the elbow is bent. This is flexion in action. Your arm extends when you straighten it, creating a wider angle between your upper and lower arms. Movements involving the midline of a structure are referred to as abduction and adduction. For instance, extending your fingers widely causes them to shift away from the hand's midline.

Functions of Saddle Joint

Like saddle joints, the majority of joints permit mobility. A saddle joint provides flexibility to move in a wide range of motions, including movement back and forth and side to side, while stabilizing the bones in the joint. The following table gives details about the functions of saddle joints-

Structure of a Saddle Joint

When one bone surface is concave and the other is convex, a saddle joint is created. The stability is greatly impacted by this.

Various Movements in Saddle Joint 

The motions of saddle joints, which include flexion, extension, adduction, abduction, and circumduction, are comparable to those of the condyloid joint. Axial rotation is not permitted, though. Biaxial saddle joints are claimed to enable mobility in both the sagittal and frontal planes. The carpometacarpal joint in the thumb, the sternoclavicular joint in the thorax, the incudomalleolar joint in the middle ear, the calcaneocuboid joint in the heel, and other joints in the human body are examples of saddle joints.

Read more about- Ellipsoid Joint.

Associate Problems with Saddle Joint

The following are some of the conditions associated with saddle joint-

Arthritis

Arthritis, a prevalent condition that affects all synovial joints, can affect saddle joints. More than 100 different forms of arthritis exist. These ailments can be brought on by misuse, aging-related wear and tear, autoimmune disorders, metabolic disorders, heredity, or infections. The most prevalent kind of arthritis is osteoarthritis. The cartilage may deteriorate as a result, leaving the saddle joint's two bones' ends exposed. Bones rubbing against one another when we walk can result in inflammation, stiffness, and discomfort in the joints. The following are other kinds of arthritis that can impact the saddle joints-

1. Gout
2. Infectious arthritis
3. Psoriatic arthritis
4. Rheumatoid arthritis
5. Spondyloarthritis

The effects of arthritis can develop, causing crippling agony and eventually causing the bones in the joint to deteriorate. As a result, the disease may make it difficult for you to utilize the afflicted joint and carry out daily activities. The following effects of arthritis in saddle joints are possible-

1. Incudomalleolar joint arthritis.
2. Sternoclavicular joint arthritis.
3. The carpometacarpal joint in the thumb has arthritis.
4. When rheumatoid arthritis is present, hearing loss occurs.

Incudomalleolar Injury

The following are the most typical reasons for damage to the incudomalleolar joint-

1. Discrepancy of the incudomalleolar joint.
2. Either fractures or head injuries.
3. Foreign object insertion in the external ear canal.
4. Infected ears.
5. Skull injury.

Sprained thumb

When the ligaments supporting the thumb are stretched beyond what they should be, it results in a sprained thumb. When you fall, your thumb may bend backward, away from the palm of your hand, or you may land on an outstretched hand. A sprained thumb is sometimes referred to as a "skier's thumb" since it frequently occurs when you fall while holding a ski pole in your hand. It is referred to as "gamekeeper's thumb" when this ailment develops over time due to repeated misuse. The ulnar collateral ligament (UCL), which is situated inside the carpometacarpal joint, is typically injured in thumb sprains. The carpometacarpal joint may become unstable due to the damage.

Sternoclavicular Injury

A modest sprain to a clavicle fracture might result in injuries to the sternoclavicular joint. The joint can be forced out of its natural position by a powerful impact. A high-impact incident, such as a hard fall, a collision during contact sports, or an auto accident, frequently results in injuries to this joint. Breathing or blood flow issues may result from the sternoclavicular joint dislocating backward, deep into the upper chest.