Enthesis is the point at which a tendon

Tendon

A tendon is a tough band of fibrous connective tissue that usually connects muscle to bone and is capable of withstanding tension. Tendons are similar to ligaments and fasciae as they are all made of collagen except that ligaments join one bone to another bone, and fasciae connect muscles to other...

 or ligament

Ligament

In anatomy, the term ligament is used to denote any of three types of structures. Most commonly, it refers to fibrous tissue that connects bones to other bones and is also known as articular ligament, articular larua, fibrous ligament, or true ligament.Ligament can also refer to:* Peritoneal...

 or muscle

Muscle

Muscle is a contractile tissue of animals and is derived from the mesodermal layer of embryonic germ cells. Muscle cells contain contractile filaments that move past each other and change the size of the cell. They are classified as skeletal, cardiac, or smooth muscles. Their function is to...

 inserts into bone

Bone

Bones are rigid organs that constitute part of the endoskeleton of vertebrates. They support, and protect the various organs of the body, produce red and white blood cells and store minerals. Bone tissue is a type of dense connective tissue...

, where the collagen

Collagen

Collagen is a group of naturally occurring proteins found in animals, especially in the flesh and connective tissues of mammals. It is the main component of connective tissue, and is the most abundant protein in mammals, making up about 25% to 35% of the whole-body protein content...

 fibers are mineralized and integrated into bone tissue. The collagen to bone interface is via Sharpey's fibers.

Classification

There are two types:

• Fibrous entheses
• Fibrocartilaginous entheses

In a fibrous enthesis, the collagenous tendon or ligament directly attaches to the bone, whilst the fibrocartilaginous enthesis displays 4 zones during the transition from tendon/ligament to bone:

• i) tendinous area displaying longitudinally oriented fibroblasts and a parallel arrangement of collagen fibres
• ii) a fibrocartilaginous region of variable thickness where the structure of the cells changes to chondrocytes
• iii) an abrupt transition from cartilaginous to calcified fibrocartilage - the so-called 'tidemark' or 'blue line'
• iv) bone

Pathology

A disease of the entheses is known as an "enthesopathy

Enthesopathy

In medicine, an enthesopathy refers to a disorder of entheses .If the condition is known to be inflammatory, it can more precisely be called a enthesitis.Enthesopathies are disorders of peripheral ligamentous or muscular attachments,...

" or "enthesitis" and is characteristic of spondyloarthropathy

Spondyloarthropathy

Spondyloarthropathy is any joint disease of the vertebral column. Spondyloarthropathy with inflammation is called spondylarthritis. In contrast, spondylopathy is a disease of the vertebra itself, but many conditions involve both spondylopathy and spondyloarthropathy...

 but is present in other pathologies as well.

The enthesis is the primary site of ankylosing spondylitis

Ankylosing spondylitis

Ankylosing spondylitis , previously known as Bekhterev's disease, Bekhterev syndrome, and Marie-Strümpell disease is a chronic inflammatory disease of the axial skeleton with variable involvement of peripheral joints and nonarticular structures...

.

External links

• Image of enthesis at Medscape
  Medscape
  Medscape is a web resource for physicians and other health professionals. It features peer-reviewed original medical journal articles, CME , a customized version of the National Library of Medicine's MEDLINE database, daily medical news, major conference coverage, and drug information—including a...
  
  
• Enthesopathy and Soft Tissue Shadows at chiroweb.com
• Origin of phrase at rheuma21st.com at rheuma21st.com