What Causes Tendons to Breakdown?
Tendon breakdown can occur in people of all ages in both the upper and lower limb, from causes such as sporting injuries or gradual wear and tear from overuse or aging.
The world’s foremost tendon pathology experts Professor Jill Cook (Monash University, Australia) and Craig Purdam (Australian Institute of Sport) have proposed a three-stage model of tendon breakdown in their landmark paper: Is tendon pathology a continuum? A pathology model to explain the clinical presentation of load-induced tendinopathy. Br J Sports Med. 2009 Jun; 43(6):409-16.
Examples of tendons in which pathological breakdown can occur include: the Achilles insertion, the gluteus medius tendon, the upper hamstrings tendon, the hip adductor tendon and supraspinatus tendon.
Histological studies of tendon injuries show the problem is a degenerative process rather than an inflammatory problem. Thus the past terminology for tendon injury tendonitis with the suffix ‘itis” means inflammation is now no longer being used, and instead the current terminology for tendon injury is tendinopathy.
In this three-stage continuum model of tendon pathology the injured tendon’s internal structure under goes pathological changes from a normal tendon, to an irritated tendon and then progressively to moderately and severely disrupted.
Stage 1: Reactive Tendinopathy
This is the first reaction of the tendon to an overload of its current capacity; the tendon cells are aggravated and irritated by the overload. Which can either be a single episode of overload or a series of exposures to excessive overload. Therefore the clinical management is directed to settling the tendon down.
Stage 2: Tendon Disrepair
In this stage changes in the tendon composition occur which results in collagen and extracellular matrix disorganization within the tendon. The extracellular matrix is beginning to breakdown.
Stage 3: Degenerative Tendinopathy
This stage is defined by severe extracellular matrix breakdown, increased vascularity and areas of cell death occur. If a degenerative tendinopathy, is extensive enough the tendon can rupture.
Professor Jill Cook classifies a common scenario we see clinically as being “reactive on degenerative”, where somebody has developed some degenerative changes in their tendon and thus they have less capacity in their musculo-tendon unit and then they participate in an activity above which they are use to, ie doing too much too soon. For example this would be the person who decides after a period of being inactive to become active and run 5km.
The continuum models guides us in the treatment process so that rehabilitation is directed at moving the person though the reactive phase and setting the tendon, so that the irritating load provoking the tendon cells is ceased. Once the tendon is settled then the long-term rehabilitation process of increasing the strength capacity of the tendon can begin. In addition any deficits in the whole kinetic chain of force transfer are addressed, ie core, arms and legs in order to prevent recurrences.
Cook JL, Purdam CR. Is tendon pathology a continuum? A pathology model to explain the clinical presentation of load-induced tendinopathy. Br J Sports Med. 2009 Jun; 43(6):409-16.
Professor Jill Cook on managing tendinopathies in 2011. 25 Nov, 2010. British Journal of Sports Medicine Podcasts.
Jill Cook on the continuum model of tendinopathy. 28 Nov, 2012. British Journal of Sports Medicine Podcasts.