Enthesis, Enthesitis and Enthesopathy - Introduction & Definition

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The enthesis is the point of insertion of tendons, or ligaments, or joint capsules to bone.

Joint ligaments tendons and joint capsules are collectively composed of tough dense connective tissues that are specially adapted at the point where they join the skeleton. This insertion region is known as an enthesis.

Most entheses throughout the body in both the spine and the peripheral skeleton and in large and small joints have a tough elasticated compressible tissue called fibrocartilage adjacent to the point of insertion.

Historically, disorders of the enthesis were very poorly researched. In this last decade it has emerged that the enthesis is "the sleeping giant" of skeletal biology.

Enthesitis plays a primary role in a group of diseases collectively called the seronegative spondyloarthropathies which includes:

  • ankylosing spondylitis
  • psoriatic arthritis
  • entheropathic arthritis
  • reactive arthritis
  • undifferentiated spondyloarthropathy

The increasingly recognised important role of the enthesis in other diseases includes:

  • osteoarthritis
  • some manifestations of Rheumatoid arthritis
  • mechanical disorders
  • athletic injuries
  • paediatric conditions
  • gout

Disorders of the enthesis are a major cause of various regional musculoskeletal problems including tennis elbow and trochanteric bursitis.

Historically the importance of enthesis as a cause of pain and suffering was overlooked for a number of reasons

  • Many insertions are inaccessible to the examining physician.
  • Many are too small to examine
  • Pain may be poorly localised
  • Tissue biopsy is difficult or even impossible and not often done
  • The anatomical structure means that swelling may not be evident
  • Blood tests that pick up inflammation or damage are often normal
  • X-rays are often normal in early disease
  • X-ray changes are common at entheses where there may be no symptoms

This site is dedicated to providing professional information on all aspects of enthesis biology with reference to diagnosis and treatment in many diseases. It is written by professionals and aimed at patients and doctors to increase knowledge and understanding of the enthesis.

Definition of Enthesitis and Enthesopathy

Many doctors don't even know what the enthesis is and could not name a disease process of the enthesis. This is because the primacy of the enthesis in many musculoskeletal conditions was not appreciated until recently.

The enthesis is the insertion point of tendons or ligaments or joint capsules to bone.

Enthesopathy describes any disease process of the enthesis.

Enthesitis defines diseases of the enthesis where inflammation is the primary problem.

An fully functioning enthesis comprises not only the insertion but also adjacent tissues and is thus called an enthesis organ.

Many entheses have adjacent tissue called synovium that provides both lubrication and nourishment for the moving parts of the enthesis.

This provides the equivalent of engine oil to the enthesis and its smooth movement just as car engine oil aids movement in that setting.

The specialised structure formed by the enthesis and the synovium is called a synovio-entheseal complex (SEC).

Enthesitis and enthesopathy can be hard to distinguish from non-inflammatory diseases of the skeleton which makes recognition difficult.

This website is devoted to all aspects of enthesis biology and pathology.

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