Joints

The skeletal system of the human body contains bones, which are rigid tissues. Bones
support body movement and posture, protect the body’s internal organs, reserve body
minerals, provide structure and support of the body and produce white and red blood cells. A
joint is a structure that separates two or more adjacent elements of the skeletal system. They
are articulation points where two or more bones meet. Joints can be classified in various
ways. When classified depending on the degree of movement permitted, we have synarthrosis
or immovable joints, slightly movable or amphiarthrosis joints, and freely movable or
diarthrosis joints. Classification can be done according to the type of tissue present in the
joint. In this classification, the joints are fibrous, cartilaginous, and synovial joints (Shier et
al., 2018). 

Fibrous joints

In a fibrous joint, there exists a tough fibrous tissue that binds the bones together. The
connective tissue consists mainly of collagen. The joints have no joint cavity. Fibrous joints
can be classified further into sutures, syndesmoses, and gomphoses. A suture is an
immovable fibrous joint. The connective tissue found in sutures is known as Sharpey’s fibers.
In the human body, sutures are located in the skull, holding the bony plates together. They
only permit minimal movement of the bones. Syndesmoses are slightly movable joints in
which interosseous ligaments join adjacent bones. An example of a syndesmosis joint is the
middle tibiofibular joint, in which the interosseous membrane runs along the crests of the two
bones. Gomphoses are fibrous immovable joints. They connect the teeth to the maxilla and
the mandible. Their movement is minimal and can be achieved by applying pressure on the
teeth (Patton & Thibodeau, 2018; Shier et al., 2018). 

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Cartilaginous joints

In these joints, the bones are joined together by cartilage. There are two types of
cartilage, hyaline cartilage containing few collagen fibers in the matrix and fibrocartilage
containing many collagen fibers. The joints allow less movement than synovial joints but
more movement than the fibrous joints. Cartilaginous joints can further be classified into
primary and secondary cartilaginous joints. Primary cartilaginous joints, also known as
synchondroses, are immovable and made up of hyaline cartilage. They are mostly found
between developing bones’ ossification centers and are rare in the mature skeleton. An
example of this joint is the epiphysis and diaphysis in a long-growing bone. In secondary
cartilaginous joints or symphyses, the bones are joined together by fibrocartilage layers. The
joints are slightly movable and are found at the midline of the skeleton. An example is the
pubic symphysis, located between the left and the right pubic bones (Patton & Thibodeau,
2018; Shier et al., 2018). 

Synovial joints

In a synovial joint, the articulating surfaces of the bones are enclosed within fluid-
filled joint capsules. This joint is found between bones that move against each other. Synovial
joints allow more movement as compared to cartilaginous and fibrous joints. They are freely
movable and are the common joints in the body. Synovial joints are made up of cartilage
covering the bone surfaces, a joint capsule enclosing the joint, synovial fluid that fills the
cavity, and a synovial membrane that produces the synovial fluid. They can be further
classified into different types depending on the movement they permit and the articular
surfaces’ shapes. A hinge permits movement in one plane, either by extension or flexion.
Examples of a hinge are the knee and elbow joints. Ball and socket joints permit free
movement in different axes, and they include the shoulder and hip joints. Other synovial

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joints are plane, ellipsoid, pivot, and saddle joints (Patton & Thibodeau, 2018; Shier et al.,
2018). 

Osteoarthritis

Osteoarthritis is a common degenerative joint disease. It can occur in any joints in the
body, but it is common in the weight-bearing joints in the knees, spine, hands, and hips
(Glyn-Jones et al., 2015). Its signs and symptoms include pain, stiffness, swelling, crackles,
and tenderness at the affected joints. The affected individual may have a joint deformity and
difficulty in walking. Osteoarthritis causes cartilage, the protective substance at the end of the
bones, to wear out, decreasing its shock-absorbing ability gradually. The cartilage becomes
stiff and loses its elasticity. As a result, the bones cannot move freel


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