Common Causes of Tendonitis:

• Repetitive strain on the tendon
  Repetitive strain is by far the most common cause of tendonitis. Repetitive strain can some in many forms and from many sources. Tendonitis of the elbow, bicep, shoulder and hand is often developed by individuals that work on factory production lines due to the repetitive nature of the work involved. Sports professionals (like golfers and tennis players) often develop tendonitis from the repetitive movements in their sports.
   
• Age related tendon changes
  As the human body gets older the tendons get harder and lose their elasticity. This means that the joint is no longer as free to move and often flexibility is lost. As individuals get older they are much more prone to develop tendonitis. The cause of tendonitis from age is still not fully understood. It's suggested that as the body ages the change in blood vessels effects the tendons.
   
• Putting the tendon under too much strain
  This is the leading cause of tendonitis amongst strength athletes and bodybuilders. Tendonitis is developed when the individual puts the tendon under too much strain without properly warming up or under strain that the tendon simply cannot handle. This tendonitis cause can easily be avoided by using correct training techniques and exercise form.
   
• As a result of injury
  It is not uncommon for tendonitis to develop as a result of another tendon or joint injury. For example, shoulder tendonitis is often developed after a rotator cuff injury and knee tendonitis can be developed after having knee surgery. In these cases tendonitis usually develops because the injury has not completely healed. This cause of tendonitis can easily be avoided by getting sufficient rest for the joint to recover from an injury completely.
   
• As a result of another condition
  In some cases diseases like rheumatoid arthritis or diabetes may cause tendonitis to occur. These cases are often rare and only occur when the individual puts the tendon under an unusual amount of pressure or strain.
   
• Thermal injury to the tendon
  Thermal injury is generally a very uncommon cause of tendonitis. Thermal injury is often experienced by outdoor mountain climbers, rock climbers and hikers. In most cases the affected areas are the hands, wrists, ankles and feet.
   
• Anatomical cause of tendonitis
  Anatomy is a rare cause of tendonitis. If the tendon does not have a smooth surface area in which to work against it will often become inflamed and irritated quite easily. In these situations surgery is often required to rectify the problem.