Tendons are tough, flexible, fibrous bands of tissue that connect muscles to bones. When tendons become inflamed, irritated or suffer microscopic tears, the condition is called tendonitis.
Symptoms of a tendon injury can include:
pain that gets worse when you move the affected area
stiffness in the affected area, which may be worse in the morning
weakness in the affected area or being unable to move a joint
a sensation that the tendon is grating or crackling as it moves
swelling, sometimes with heat or redness
a lump on the affected 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.
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).