From en.wikipedia.org:
[Location at which two or more bones make contact] [other uses] {{Infobox
anatomy | Name = Joint | Latin = articulus,<br />junctura,<br />articulatio |
Greek = | Image = Joint.svg | Caption = Diagram of a typical synovial joint |
Width = 300 | Image2 = Gray298.png | Caption2 = Depiction of an intervertebral
disc, a cartilaginous joint | Precursor = | System = Musculoskeletal system<br
/>Articular system | Artery = | Vein = | Nerve = | Lymph = }} A JOINT or
ARTICULATION (or ARTICULAR SURFACE) is the connection made between bones,
ossicles, or other hard structures in the body which link an animal's skeletal
system into a functional whole.[1][2][3] They are constructed to allow for
different degrees and types of movement. Some joints, such as the knee,
elbow, and shoulder, are self-lubricating, almost frictionless, and are able
to withstand compression and maintain heavy loads while still executing smooth
and precise movements.<ref name="Saladinp274"/> Other joints such as sutures
between the bones of the skull permit very little movement (only during birth)
in order to protect the brain and the sense organs.<ref name="Saladinp274"/>
The connection between a tooth and the jawbone is also called a joint, and is
described as a fibrous joint known as a gomphosis. Joints are classified both
structurally and functionally.[4]
Joints play a vital role in the human body, contributing to movement,
stability, and overall function. They are essential for mobility and
flexibility, connecting bones and facilitating a wide range of motions, from
simple bending and stretching to complex actions like running and jumping.
Beyond enabling movement, joints provide structural support and stability to
the skeleton, helping to maintain posture, balance, and the ability to bear
weight during daily activities.
The clinical significance of joints is highlighted by common disorders that
affect their health and function. OSTEOARTHRITIS, a degenerative joint
disease, involves the breakdown of cartilage, leading to pain, stiffness, and
reduced mobility. RHEUMATOID ARTHRITIS, an autoimmune disorder, causes
chronic inflammation in the joints, often resulting in swelling, pain, and
potential deformity. Another prevalent condition, GOUT, arises from the
accumulation of uric acid crystals in the joints, triggering severe pain and
inflammation.
Joints also hold diagnostic importance, as their condition can indicate
underlying health issues. Symptoms such as joint pain and swelling may signal
inflammatory diseases, infections, or metabolic disorders. Effective
treatment and management of joint-related conditions often require a
multifaceted approach, including physical therapy, medications, lifestyle
changes, and, in severe cases, surgical interventions. Preventive care, such
as regular exercise, a balanced diet, and avoiding excessive strain, is
critical for maintaining joint health, preventing disorders, and improving
overall quality of life.
** Classification
The number of joints depends on if sesamoids are included, age of the human
and the definition of joints. However, the number of sesamoids is the same in
most people with variations being rare.[5][6][7]
Joints are mainly classified structurally and functionally. Structural
classification is determined by how the bones connect to each other, while
functional classification is determined by the degree of movement between the
articulating bones. In practice, there is significant overlap between the two
types of classifications.
*** Clinical, numerical classification
- monoarticular – concerning one joint
- oligoarticular or pauciarticular – concerning 2–4 joints
- polyarticular – concerning 5 or more joints
*** Structural classification (binding tissue)
Structural classification names and divides joints according to the type of
binding tissue that connects the bones to each other.<ref
name="Whiting2006p40"/> There are four structural classifications of
joints:[8]
- fibrous joint – joined by dense regular connective tissue that is rich in collagen fibers [9]
- cartilaginous joint – joined by cartilage . There are two types: primary cartilaginous joints composed of hyaline cartilage , and secondary cartilaginous joints composed of hyaline cartilage covering the articular surfaces of the involved bones with fibrocartilage connecting them.
- synovial joint – not directly joined – the bones have a synovial cavity and are united by the dense irregular connective tissue that forms the articular capsule that is normally associated with accessory ligaments. <ref name="anatomical"/>
- facet joint – joint between two articular processes between two vertebrae. [10] [11]
*** Functional classification (movement)
Joints can also be classified functionally according to the type and degree of
movement they allow:<ref name="Whiting2006p40"/>[12] Joint movements are
described with reference to the basic anatomical planes.<ref
name="Saladinp274"/>
- synarthrosis – permits little or no mobility. Most synarthrosis joints are fibrous joint s, such as skull sutures. This lack of mobility is important, because the skull bones serve to protect the brain. [13]
- amphiarthrosis – permits slight mobility. Most amphiarthrosis joints are cartilaginous joint s. An example is the intervertebral disc . Individual intervertebral discs allow for small movements between adjacent vertebrae, but when added together, the vertebral column provides the flexibility that allows the body to twist, or bend to the front, back, or side. <ref name="openstax"/>
- synovial joint (also known as a _diarthrosis_ ) – freely movable. <ref name="Whiting2006p40"/> <ref name="umich2010ClByMov"/> Synovial joints can in turn be classified into six groups according to the type of movement they allow: plane joint , ball and socket joint , hinge joint , pivot joint , [14] [15] condyloid joint and saddle joint . [16]
Joints can also be classified, according to the number of axes of movement
they allow, into nonaxial (gliding, as between the proximal ends of the ulna
and radius), monoaxial (uniaxial), biaxial and multiaxial.[17] Another
classification is according to the degrees of freedom allowed, and
distinguished between joints with one, two or three degrees of freedom.<ref
name="Platzer2008p28"/> A further classification is according to the number
and shapes of the articular surfaces: flat, concave and convex surfaces.<ref
name="Platzer2008p28"/> Types of articular surfaces include trochlear
surfaces.[18]
*** Biomechanical classification
Joints can also be classified based on their anatomy or on their biomechanical
properties. According to the anatomic classification, joints are subdivided
into _simple_ and _compound_, depending on the number of bones involved, and
into _complex_ and _combination_ joints:[19]
1. Simple joint: two articulation surfaces (e.g. shoulder joint , hip joint )
2. Compound joint: three or more articulation surfaces (e.g. radiocarpal joint )
3. Complex joint: two or more articulation surfaces and an articular disc or meniscus (e.g. knee joint )
===Anatomical=== <!--joint groups redirects here--> The joints may be
classified anatomically into the following groups:
1. Joints of hand
2. Elbow joints
3. Wrist joints
4. Axillary joints
5. Sternoclavicular joint s
6. Vertebral articulation s
7. Temporomandibular joint s
8. Sacroiliac joint s
9. Hip joint s
10. Knee joint s
11. Articulations of foot
Unmyelinated nerve fibers are abundant in joint capsules and ligaments, as
well as in the outer part of intra-articular menisci. These nerve fibers are
responsible for pain perception when a joint is strained.[20]
** Clinical significance
[Arthropathy] Damaging the cartilage of joints (articular cartilage) or the
bones and muscles that stabilize the joints can lead to joint dislocations and
osteoarthritis. Swimming is a great way to exercise the joints with minimal
damage.<ref name="Saladinp274"/>
A joint disorder is termed arthropathy, and when involving inflammation of one
or more joints the disorder is called arthritis. Most joint disorders involve
arthritis, but joint damage by external physical trauma is typically not
termed arthritis.
Arthropathies are called _polyarticular_ (multiarticular) when involving many
joints and _monoarticular_ when involving only a single joint.
Arthritis is the leading cause of disability in people over the age of 55.
There are many different forms of arthritis, each of which has a different
cause. The most common form of arthritis, osteoarthritis (also known as
degenerative joint disease), occurs following trauma to the joint, following
an infection of the joint or simply as a result of aging and the deterioration
of articular cartilage. Furthermore, there is emerging evidence that abnormal
anatomy may contribute to early development of osteoarthritis. Other forms of
arthritis are rheumatoid arthritis and psoriatic arthritis, which are
autoimmune diseases in which the body is attacking itself. Septic arthritis
is caused by joint infection. Gouty arthritis is caused by deposition of uric
acid crystals in the joint that results in subsequent inflammation.
Additionally, there is a less common form of gout that is caused by the
formation of rhomboidal-shaped crystals of calcium pyrophosphate. This form
of gout is known as pseudogout.
Temporomandibular joint syndrome (TMJ) involves the jaw joints and can cause
facial pain, clicking sounds in the jaw, or limitation of jaw movement, to
name a few symptoms. It is caused by psychological tension and misalignment
of the jaw (malocclusion), and may be affecting as many as 75 million
Americans.<ref name="Saladinp274"/>
** History
*** Etymology
The English word _joint_ is a past participle of the verb _join_, and can be
read as _joined_.[21] Joint is derived from Latin _iunctus_,<ref
name="Klein1971"/> past participle of the Latin verb _iungere_, join, unite,
connect, attach.[22]
The English term _articulation_ is derived from Latin _articulatio_.<ref
name="Klein1971"/>
Humans have also developed lighter, more fragile joint bones over time due to
the decrease in physical activity compared to thousands of years ago.[23]
** See also
- Arthrology
- Cracking joints
- Kinesiology
- Ligament
- Development of joints
** References
[reflist]
** External links
[Joints]
- Synovial joints Illustrations and Classification (see http://www.sports-db.com/home/information/joints.html)
[Human systems and organs] [Joints] [Cranial fibrous joints] [Joints of head
and neck] [Joints of torso] [Joints of upper limbs] [Joints of lower limbs]
[Authority control]
Category:Skeletal system