The term tendinitis is not used so much now as tendon pain has moved away from an inflammatory model where large amounts of inflammatory chemicals are present. The current thinking is that the tendon is in a state of degeneration.
What is a Tendinopathy?
Put simply, it is an Injury to the tendon. If the tendon is overloaded and continues to be overloaded it will not have the appropriate rest period to heal. This can lead to Tendinopathy. There are changes within the structure of the tendon and these can often be irreversible. Tendinopathies can occur where the tendon has become overloaded or in fact unloaded (stress-shielded) and where a direct blow is involved.
Tendinopathies can be developing in the background with no feelings of pain. Often the tendon can become thickened than the other side, eventually, this can lead to Tendinopathy.
Examples of overloading situations include an increase in the volume or intensity of exercise or a new type of exercise. A good example is when you add in an extra walk during the week or if you increase mileage when running or have just taken up running.
The 3 phases of a Tendinopathy
A group of Australian Scientists who are at the forefront of tendon pain developed the concept that tendon pain is part of a continuum i.e. a progressive injury that can move forward or backwards along the continuum. The three stages are:
This is an acute onset of pain, very much associated with an increase in load e.g. pre-season training or increasing activity. Biologically there is an increase in protein production within the tendon in response to the excess load. There can be thickening of the tendon which helps to spread the load over an increased cross sectional area which will allow the tendon to adapt. In this stage, a full recovery to a normal tendon can be achieved if enough time is given between loading sessions allowing the tendon to adapt.
This phase will occur if insufficient unloading of the tendon is not allowed. It is the phase where the tendon is attempting to heal itself. It is similar to the reactive phase with increase in proteins, but there is marked breakdown of the cell matrix, disorganization of the cells, increase in blood flow and neuronal growth. The tendon will be swollen due to the above changes. With the appropriate management of load and exercise some of the above changes can be reversed.
This phase is a progression of cell disorganization to a point where some parts of the tendon now have signs of cell death. There are large areas of blood vessels and large swelling can be apparent. This phase is unlikely to go backward on the continuum. If sufficient high load is applied there is a good chance that the tendon will rupture.
Cook and Purdam 2009. Is tendon pathology a continuum? A pathology model to explain the clinical presentation of load-induced tendinopathy. British Journal of Sports Medicine.