A synovial joint is of six different types and are mainly classified based on movement. This joint is mainly formed between the bones, whose articulating surfaces have both concave and convex regions.
These include joints at the base of the thumb finger, upper part of the breastbone and the incudomalleolar joint, which is located in the inner human ear. The name saddle joint is mainly derived from its shape or structure.
The connecting bones are shaped like interlocking saddles. This article concludes with an introduction to saddle joints, their types, structure and functions.
DetailsIdentifiers Latin articulation sellers TA98A03.0.00.048TA21560FMA75298 Anatomical terminology A saddle joint (seller joint, articulation by reciprocal reception) is a type of synovial joint in which the opposing surfaces are reciprocally concave and convex. It is one of the five types of synovial joints in the human skeletal system.
The bone resting on the saddle moves in an oval shape quite similar to a condyloid joint. The types of movement a saddle joint allows are flexion, extension, adduction and abduction.
All types of gripping motion are provided by saddle joint such as using a pen, grasping your mobile phone and steering the wheel of your car. Because of synovial joints, people were able to move freely.
Synovial joints enable you to walk, run, type, and write. They are a complex joints characterized by articular cartilage that covers the ends of the bone.
They have articular capsule containing fibrous connective tissues and lined with synovial membrane. They contain synovial fluid and ligaments and their role is to hold the bones together.
Photo 2: A table presentation of the different types of synovial joints in the human body Picture Source: www2.highlands.edu Synovial joints are grouped according to its shape and structure.
The shape and structure of the joints can significantly affect the body’s movement. An example of plane joint is carpal bones in the hand.
The vertebrae and tarsal bones of the feet are also examples of planar joint. The ball and socket joints permit a full range of motion.
The bone that sits on the saddle can mimic the movement of the condyloid joint. Saddle joints allow you to flex, extend, abduct, and addict the bones.
Specifically, the saddle joint structure is at the base of the thumb (carpal and metacarpal). The patella that sits on the knee looks like a saddle, but is not considered a joint.
The primary bones in the ankle are talus, tibia, and fibula. Function wise, it is categorized as a hinge joint because it allows dorsiflexion and plantar flexion of the foot.
You use the saddle joint to hold the tennis racket and golf club. Saddle joints are also useful in productive movements like writing, sewing, painting a portrait, and pottery.
Bowling in cricket makes use of the pivot joint found in the forearm. In football, catching the ball using the head would need the help of the pivot joint found in the neck.
Basically, any sports that require turning of the head uses pivot joints. The articulating surfaces of the bones are covered by a thin layer of articular cartilage.
Friction between the bones at a synovial joint is prevented by the presence of the articular cartilage, a thin layer of healing cartilage that covers the entire articulating surface of each bone. However, unlike at a cartilaginous joint, the articular cartilages of each bone are not continuous with each other.
Lining the inner surface of the articular capsule is a thin synovial membrane. This fluid also provides nourishment to the articular cartilage, which does not contain blood vessels.
These strengthen and support the joint by anchoring the bones together and preventing their separation. Ligaments are classified based on their relationship to the fibrous articular capsule.
A tendon is the dense connective tissue structure that attaches a muscle to bone. This type of indirect support by muscles is very important at the shoulder joint, for example, where the ligaments are relatively weak.
A few synovial joints of the body have a fibrocartilage structure located between the articulating bones. This is called an articular disc, which is generally small and oval-shaped, or a meniscus, which is larger and C-shaped.
These structures can serve several functions, depending on the specific joint. In some places, an articular disc may act to strongly unite the bones of the joint to each other.
Examples of this include the articular discs found at the sternoclavicular joint or between the distal ends of the radius and ulna bones. Finally, an articular disc can serve to smooth the movements between the articulating bones, as seen at the temporomandibular joint.
Bursae reduce friction by separating the adjacent structures, preventing them from rubbing directly against each other. Examples include the subacromial bursa that protects the tendon of shoulder muscle as it passes under the acromial of the scapula, and the suprapatellar bursa that separates the tendon of the large anterior thigh muscle from the distal femur just above the knee.
Figure 9.9Bursae Bursae are fluid-filled sacs that serve to prevent friction between skin, muscle, or tendon and an underlying bone. Three major bursae and a fat pad are part of the complex joint that unites the femur and tibia of the leg.
It contains a lubricating fluid that allows for smooth motions of the tendon during muscle contraction and joint movements. This will cause pain, swelling, or tenderness of the bursa and surrounding area, and may also result in joint stiffness.
Bursitis is most commonly associated with the bursae found at or near the shoulder, hip, knee, or elbow joints. It can arise from muscle overuse, trauma, excessive or prolonged pressure on the skin, rheumatoid arthritis, gout, or infection of the joint.
Repeated acute episodes of bursitis can result in a chronic condition. Pivot Joint At a pivot joint, a rounded portion of a bone is enclosed within a ring formed partially by the articulation with another bone and partially by a ligament (see Figure 9.10 a).
Here, the upward projecting dens of the axis articulates with the inner aspect of the atlas, where it is held in place by a ligament. Here, the head of the radius is largely encircled by a ligament that holds it in place as it articulates with the radial notch of the ulna.
A good example is the elbow joint, with the articulation between the trachea of the humerus and the cochlear notch of the ulna. This joint provides the thumb the ability to move away from the palm of the hand along two planes.
This movement of the first carpometacarpal joint is what gives humans their distinctive “opposable” thumbs. The motion at this type of joint is usually small and tightly constrained by surrounding ligaments.
Based only on their shape, plane joints can allow multiple movements, including rotation. However, not all of these movements are available to every plane joint due to limitations placed on it by ligaments or neighboring bones.
At the hip joint, the head of the femur articulates with the acetabulum of the hip bone, and at the shoulder joint, the head of the humerus articulates with the glenoid cavity of the scapula. The femur and the humerus are able to move in both anterior-posterior and medial-lateral directions, and they can also rotate around their long axis.
The shallow socket formed by the glenoid cavity allows the shoulder joint an extensive range of motion. Arthritis may arise from aging, damage to the articular cartilage, autoimmune diseases, bacterial or viral infections, or unknown (probably genetic) causes.
The most common type of arthritis is osteoarthritis, which is associated with aging and “wear and tear” of the articular cartilage (Figure 9.11). Risk factors that may lead to osteoarthritis later in life include injury to a joint; jobs that involve physical labor; sports with running, twisting, or throwing actions; and being overweight.
As the articular cartilage layer wears down, more pressure is placed on the bones. In individuals with more advanced osteoarthritis, the affected joints can become more painful and therefore are difficult to use effectively, resulting in increased immobility.
Treatments may include lifestyle changes, such as weight loss and low-impact exercise, and over-the-counter or prescription medications that help to alleviate the pain and inflammation. For severe cases, joint replacement surgery (arthroplasty) may be required.
However, arthroplasty can provide relief from chronic pain and can enhance mobility within a few months following the surgery. This type of surgery involves replacing the articular surfaces of the bones with prosthesis (artificial components).
For example, in hip arthroplasty, the worn or damaged parts of the hip joint, including the head and neck of the femur and the acetabulum of the pelvis, are removed and replaced with artificial joint components. The acetabulum of the pelvis is reshaped and a replacement socket is fitted into its place.
The parts, which are always built in advance of the surgery, are sometimes custom-made to produce the best possible fit for a patient. Gout is a form of arthritis that results from the deposition of uric acid crystals within a body joint.
Gout occurs when the body makes too much uric acid or the kidneys do not properly excrete it. A diet with excessive fructose has been implicated in raising the chances of a susceptible individual developing gout.
Other forms of arthritis are associated with various autoimmune diseases, bacterial infections of the joint, or unknown genetic causes. Autoimmune diseases, including rheumatoid arthritis, scleroderma, or systemic lupus erythematous, produce arthritis because the immune system of the body attacks the body joints.
In rheumatoid arthritis, the joint capsule and synovial membrane become inflamed. Rheumatoid arthritis is also associated with lung fibrosis, vasculitis (inflammation of blood vessels), coronary heart disease, and premature mortality.
Exercise, anti-inflammatory and pain medications, various specific disease-modifying anti-rheumatic drugs, or surgery are used to treat rheumatoid arthritis. Visit this website to learn about a patient who arrives at the hospital with joint pain and weakness in his legs.