What causes tendonitis

What causes tendonitis?

What are tendons? What is tendonitis?

Tendonitis, also known as tendinitis, is an inflammatory condition which involves the tendons in our body. We call tendons the soft but strong and flexible tissue cord-like structures that connect our muscles to our bones. They are located where the muscles narrow down to attach to a bone. While the muscle is fleshy and elastic, the tendons are denser and fibrous.The tendons serve for transmitting the pull of the muscle to the bone and thus cause movement. After a tendon injury, an inflammation develops in the tendon, and this inflammation is called tendonitis. This condition may occur in body parts such as elbows, ankles, knees, wrists, fingers, thighs and feet. It is important to mention the fact that tendonitis and tendinosis are not one and the same condition. Both of them describe a problem with tendons and could be caused by overuse, but tendonitis implies an ongoing tendon inflammation, whereas tendinosis means the tendon is enlarged and thickened/swelled. These conditions require different treatment.

What causes tendonitis?

The condition called tendonitis is most common in the shoulder, elbow, knee, wrist and heel, but it can occur anywhere that tendons are found in our body. The most usual causes of tendinitis are said to be either a repetitive but minor impact on the affected area (the more common of the two), or a sudden, more serious injury. The former is addressed by specialists as “repetitive stress or overuse”. Many people develop tendinitis because their job or hobbies implicate repetitive motions and these stress the tendons that are needed to perform the tasks. It is also believed that tendinitis is a common condition amongst the so-called “weekend warriors,” who are people who play and do exercise hard only during weekends. Here are some examples illustrating the repetitive activities as a result of which one could develop tendonitis:

Repetitive activities

  • When a person is painting the ceiling of their house for many hours
  • When a person is sitting on the computer for too long with an improper body position while using their keyboard
  • When a person is chopping, cutting or sawing. Tendonitis may occur in a few hours or on the next day.
  • When a person is clenching some hand tools too tight
  • When a person is driving for long hours with no rest
  • In a game of tennis, when a person is using a backhand/due to improper technique
  • When a person is running and wearing improper running shoes and/or has not stretched the way they are supposed to (or in other words warmed up or conditioned) before running.
  • When a person is skiing
  • When a person is playing golf etc.


As we already mentioned, tendonitis may occur after a sudden injury done to the tendons. Sharp and sudden movements such as jumping or throwing may do some damage to the tendon or a tear in its structure and after that an inflammation occurs. Even though an injury is one of the more common causes of tendonitis, it is not the most usual. We already mentioned the most usual one – repetitive activities.


  • Dog/cat bite
  • Occasionally, an infection can be the cause of tendinitis, especially an infection from a cat or dog bite to the hand or a finger.
  • Gonorrhea
    There are some cases when tendonitis is caused by the infection called gonorrhea, but this is a rare occasion.
  • Diabetes
    Tendonitis is common in people who suffer from diabetes. One explanation for that could be that “the blood supply to tendons is normally pretty sparse, so very early diabetic changes in blood vessels may show up first in tendons.”
  • Rheumatoid/psoriatic arthritis, gout, thyroid disorders, kidney diseases
    People who suffer from one of these conditions have an increased chance of developing tendinitis.


Elder people are more prone to suffer from tendinitis as tendons become less and less flexible as the body ages thus they become more susceptible to injuries.


At times, there is an anatomical cause for tendon disorders. This could be an abnormal or poorly positioned bone or joint (for example different leg length or arthritis in a joint).

Fluoroquinolone antimicrobial drugs/ciprofloxacin/levofloxacin

A newly discovered probable cause of some tendon disorders is fluoroquinolone antimicrobial drugs (a kind of antibiotic). A warning has been issued that these drugs may provide for an increased risk of tendinitis and tendon tear. In addition, the use of certain antibiotics, such as ciprofloxacin or levofloxacin, is also discovered to be a probable cause of tendonitis. There is still not certain answer to the question why this happens. Drugs that lower cholesterol are also among the drugs that may in a way lead to an increased tendonitis risk.
All of these conditions may be associated with a tendon’s “lack of ability to properly heal itself”. Tendonitis can occur anywhere in the body. Here are some of the more typical spots and the causes of tendonitis at each spot:

Tendonitis in the shoulder

In the majority of cases, the shoulder tendon (supraspinatus tendon) becomes injured by overuse, typically when the person practices a sport that requires the arm to be repeatedly raised. The typical suffering patient is a middle-aged man and the pain is located at the dominant hand (that is, if the dominant hand is the right one, the tendon problem is in the right shoulder). Here are some of the groups which are more at risk of developing shoulder tendonitis: carpenters, painters, swimmers, tennis players and baseball players.

Tendonitis in the elbow

Both forms of elbow tendonitis are very usual injuries from tendon overuse and are typically found among athletes who participate in throwing and racquet sports. Here are the two types:

Lateral epicondylitis (tennis elbow)

This tendon condition is said to affect about half of all adult athletes who take part it racquet sports. However, it is also found among people who repeatedly twist and flex their wrists, for example pulling weeds, using a screwdriver or even when carrying a briefcase.

Medial epicondylitis (golfer’s elbow)

This condition is less common than the previous one. It could be triggered by repeated sports activities such as throwing a baseball of swinging a golf club, but is more strongly related to construction work than to sports.

Tendonitis in the knee

Again, this is a common overuse injury, in most cases found in basketball players and long-distance runners.

Tendonitis in the wrist

Typically occurs in people who repeatedly grasp or pinch something with the thumb, although there are cases in which it develops during pregnancy. The pain is situated at the back of the wrist, at the base of the thumb.

Achilles tendonitis

Achilles tendonitis is a type of tendonitis which accounts for about 15% of all injuries that are due to running. Usually, it is caused by repetitive overuse of the Achilles tendon. It may also be triggered by wearing inappropriate running shoes or if you have a bad technique when running.

Tendonitis could make our lives really difficult for a long time, so we should carefully treat this condition. Being aware of the causes of it and thus trying to avoid them may help us prevent it. It is important to know that we should always contact a physician to get a better understanding of tendonitis and an adequate treatment. Health always comes first!

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