Tendonitis

Tendons are strong bands or cords of tissue that attach muscle to bone. They help move the bones and joints when muscles contract.
The main types of tendon injury are:

• Tendonitis – inflammation of a tendon
  Tendinopathy – the gradual deterioration of a tendon
  Tenosynovitis – inflammation of the protective sheath that surrounds a tendon
  Tendon rupture – a sudden tear in a tendon

Tendon injuries usually happen during sports or activities that involve sudden, sharp movements, such as throwing or jumping, or after repeated overuse of the tendons, such as running. Symptoms of a Tendon Injury
They can also be caused by repetitive daily activities, such as regularly using a computer keyboard and mouse. This is known as a repetitive strain injury (RSI).

When to see your doctor
Minor tendon injuries can often be treated at home (see below). They will usually get better in a few weeks. See your GP if your symptoms are severe or don’t start to improve within a few weeks, or if you think you may have ruptured a tendon. Treating Tendon Injury

Your GP will usually be able to diagnose a tendon injury by asking about your symptoms and examining the affected area. Occasionally, they may request an X-ray, ultrasound scan or magnetic resonance imaging (MRI) scan to confirm the diagnosis.
Some medications may be related to tendon injuries, such as fluoroquinolone antibiotics and statins, so your GP may stop these if you’re taking them.

Source: NHS UK

http://www.nhs.uk/conditions/tendonitis/Pages/Introduction.aspx