The enthesis (plural entheses) is the

connective tissue Connective tissue is one of the four primary types of animal tissue, a group of cells that are similar in structure, along with epithelial tissue, muscle tissue, and nervous tissue. It develops mostly from the mesenchyme, derived from the mesod ...

which attaches

tendon A tendon or sinew is a tough band of fibrous connective tissue, dense fibrous connective tissue that connects skeletal muscle, muscle to bone. It sends the mechanical forces of muscle contraction to the skeletal system, while withstanding tensi ...

s or

ligament A ligament is a type of fibrous connective tissue in the body that connects bones to other bones. It also connects flight feathers to bones, in dinosaurs and birds. All 30,000 species of amniotes (land animals with internal bones) have liga ...

s to a

bone A bone is a rigid organ that constitutes part of the skeleton in most vertebrate animals. Bones protect the various other organs of the body, produce red and white blood cells, store minerals, provide structure and support for the body, ...

. There are two types of entheses: ''

fibrous Fiber (spelled fibre in British English; from ) is a natural or artificial substance that is significantly longer than it is wide. Fibers are often used in the manufacture of other materials. The strongest engineering materials often inco ...

entheses'' and ''

fibrocartilaginous Fibrocartilage consists of a mixture of white fibrous tissue and Cartilage, cartilaginous tissue in various proportions. It owes its inflexibility and toughness to the former of these constituents, and its Elasticity (physics), elasticity to the ...

entheses''. In a fibrous enthesis, the collagenous tendon or ligament directly attaches to the bone. In a fibrocartilaginous enthesis, the interface presents a gradient that crosses four transition zones: # Tendinous area displaying longitudinally oriented

fibroblast A fibroblast is a type of cell (biology), biological cell typically with a spindle shape that synthesizes the extracellular matrix and collagen, produces the structural framework (Stroma (tissue), stroma) for animal Tissue (biology), tissues, and ...

s and a parallel arrangement of collagen fibres # Fibrocartilaginous region of variable thickness where the structure of the cells changes to

chondrocyte Chondrocytes (, ) are the only cells found in healthy cartilage. They produce and maintain the cartilaginous matrix, which consists mainly of collagen and proteoglycans. Although the word '' chondroblast'' is commonly used to describe an immatu ...

s # Abrupt transition from cartilaginous to calcified fibrocartilage—often called 'tidemark' or 'blue line' # Bone

Clinical significance

A disease of the entheses is known as an ''

enthesopathy An enthesopathy refers to a disorder involving the attachment of a tendon or ligament to a bone. This site of attachment is known as the entheses, enthesis (pl. entheses). If the condition is known to be Inflammation, inflammatory, it can more pr ...

'' or ''

enthesitis Enthesitis is inflammation of the entheses (singular: enthesis), the sites where tendons, ligaments and joint capsules attach to bones. It is a type of enthesopathy, meaning any pathologic condition of the entheses, with or without inflammati ...

''. Enthetic degeneration is characteristic of

spondyloarthropathy Spondyloarthritis (SpA), also known as spondyloarthropathy, is a collection of syndromes connected by genetic predisposition and clinical symptoms. The best-known subtypes are enteropathic arthritis (EA), psoriatic arthritis (PsA), ankylosing ...

and other pathologies. The enthesis is the primary site of disease in

ankylosing spondylitis Ankylosing spondylitis (AS) is a type of arthritis from the disease spectrum of axial spondyloarthritis. It is characterized by long-term inflammation of the joints of the spine, typically where the spine joins the pelvis. With AS, eye and bow ...

Society and culture

Bioarchaeology

Entheses are widely recorded in the field of

bioarchaeology Bioarchaeology (osteoarchaeology, osteology or palaeo-osteology) in Europe describes the study of biological remains from archaeological sites. In the United States it is the scientific study of human remains from archaeological sites. The term ...

, in which the presence of anomalies at these sites, called entheseal changes, has been used to infer repetitive loading to study the division of labour in past populations. Several different recording methods have been proposed to record the variety of changes seen at these sites. Previous studies have shown that, whichever recording method is used, certain entheseal changes occur more frequently in older individuals. Moreover, research demonstrates that diseases, such as

and

calcific tendinitis Calcific tendinitis is a common condition where deposits of calcium phosphate form in a tendon, sometimes causing pain at the affected site. Deposits can occur in several places in the body, but are by far most common in the rotator cuff of the s ...

, also have to be taken into consideration. Nevertheless, experimental studies relying on virtual anthropological methods of analysis (e.g.,"Validated Entheses-based Reconstruction of Activity" 1.0 and 2.0 ) have demonstrated how loading history (physical activity) can increase the relative three-dimensional (3D) size of muscle attachment sites and their subtle surface changes.

History

"Enthesis" is rooted in the

Ancient Greek Ancient Greek (, ; ) includes the forms of the Greek language used in ancient Greece and the classical antiquity, ancient world from around 1500 BC to 300 BC. It is often roughly divided into the following periods: Mycenaean Greek (), Greek ...

word, "ἔνθεσις" or "énthesis," meaning “putting in," or "insertion." This refers to the role of the enthesis as the site of attachment of bones with tendons or ligaments. Relatedly, in muscle terminology, the

insertion Insertion may refer to: *Insertion (anatomy), the point of a tendon or ligament onto the skeleton or other part of the body *Insertion (genetics), the addition of DNA into a genetic sequence *Insertion, several meanings in medicine, see ICD-10-PCS ...

is the site of attachment at the end with predominant movement or action (opposite of the origin). Thus the words (''enthesis'' and ''insertion'' f muscle are proximal in the

semantic field In linguistics, a semantic field is a related set of words grouped semantically (by meaning) that refers to a specific subject.Howard Jackson, Etienne Zé Amvela, ''Words, Meaning, and Vocabulary'', Continuum, 2000, p14. The term is also used in ...

, but ''insertion'' in reference to muscle can refer to any relevant aspect of the site (i.e., the attachment per se, the bone, the tendon, or the entire area), whereas ''enthesis'' refers to the attachment per se and to ligamentous attachments as well as tendinous ones.

References

External links

Enthesis information site
at www.enthesis.info
Image of enthesis
at

Medscape Medscape is a website providing access to medical information for clinicians and medical scientists; the organization also provides continuing education for physicians and other health professionals. It references medical journal articles, Con ...

Enthesopathy and Soft Tissue Shadows
at chiroweb.com