Tendinitis, Tendinosis, or Tenosynovitis?

Achilles tendinopathy refers to any injury to your Achilles tendon. The suffix “pathy” means suffering or disease, therefore tendinopathy is a general term that can describe any condition of a tendon. To be more specific about the type of injury that has occurred in a tendon, the termstendonitis (also spelled tendinitis), tendinosis, and tenosynovitis are used.


Achilles Tendinosis

The term tendinosis refers to the non-inflammatory, degeneration of the collagen fibers in a tendon. This tissue break down is often caused by repetitive stress on the tendon fibers and the failure for the fibers to heal. In fact, the rate oftissue damage exceeds the healing process and eventually the accumulation of damage on the Achilles tendon is not able to heal properly. The collagen fibers deteriorate to a point where the once straight, strong, flexible bundle is weakened by abnormally formed fibers that look more like a mess of strands.

Since there is no inflammation with tendinosis you will not experience swelling, heat or redness. However, you will experience pain, tenderness and stiffness at the back of the ankle where the tissue degeneration has occurred. This is the most common among Achilles tendon injuries.


Achilles Tendinitis

The suffix “itis” means something is inflamed, therefore, the term Achilles tendinitis (tendonitis) is usedwhen the Achilles tendon is inflamed. Inflammation in the Achilles tendon is oftendue to irritation and/or micro-tearing of the collagen fibers. When the fibers tear, they become weaker, inflamed and swollen causing pain and tenderness in the area.

There are 2 types of tendonitis, acute and chronicAcute tendonitis refers to inflammation that comes on suddenly, usually from a tendon strain or overloading it during exercise. Chronic tendonitis occurs over time and generally results from long term repetitive use of the Achilles tendon.

With both types of tendinitis, scar tissue develops on the Achilles tendon as the tears begin to heal. This scar tissue mends the tears in an abnormal way leaving the collagen fibers weaker and more prone to further injury. In the case of chronic tendinitis a node of scar tissue may form and/or the Achilles tendon may actually become thicker with a build up of scar tissue over a long period of time.

People with Achilles tendon pain often call their injury tendonitis however, in reality, Achilles tendinitis is a rare occurrence. Tendinosis is a more common Achilles injury.


Achilles Tenosynovitis

Tenosynovitis, also called paratendonitis (or peritendinitis), is a term used to describe inflammation and degeneration of the tendon’s outer layer or sheath. Depending on the tendon, the sheath is also called the synovium or paratenon. The Achilles tendon sheath is called the paratenon, which explains why the term paratenonitis has become a popular term for this condition as well.

It is possible to suffer from tenosynovitis alone or in conjunction with the degeneration of the Achilles tendon, Achilles tendinosis. In either case, as your body tries to heal, scar tissue forms inside the sheath attaching the inner tissues of the Achilles tendon to its outer covering, the paratenon. This scar tissue limits the gliding movement of the tendon in the paratenon, reducing the range of motion and causing pain, tenderness, redness and swelling.