Types of Tendon Pain
Tendons are composed of highly organized connective tissue which can resist high tensile stresses. The function of a tendon is to connect a muscle to a bone which allows for movement. Normal tendon is made up of primarily two connective tissue types:
- Collagen – mostly type I, makes up 60-80% of a tendon
- Elastin – 1-2% of a tendon
The two main diagnoses of tendon pain are tendinitis and tendinosis. While tendonitis is commonly diagnosed in patients thought to have tendon-related pain, research suggests the problem is actually tendinosis. The difference is appreciated at the microscopic level.
Tendinitis
Tendinitis is inflammation of the tendon which occurs secondary to microtears. These microtears happen due to the tendon being suddenly overstretched or overloaded with tensile forces.
Tendinosis
Tendinosis is degeneration of the tendon’s collagen, due to chronic overuse. Even small movements can create tendinosis over time. The microscopic changes include:
- The normal Type I collagen fibers are replaced with immature type III collagen fibers.
- This disrupts the overall collagen continuity so that they are no longer aligned in a way that best facilitates load bearing.
- There is an increase in ground substance (the material between collagen fibers).
- Vascularization (development of blood vessels) becomes disorganized and does not contribute to the healing process. This is called neovascularization.
