A biomechanical approach to Achilles tendinopathy management

Achilles tendinopathy (AT) is a debilitating condition affecting active and inactive subjects. The aetiology of AT is contentious but most theoretical models are underpinned by the same core elements: increased tendon stress that exceeds the ability of the tendon to repair, eventually leading to tissue degradation. Proposed risk factors affect tissue load or the ability of the tendon to repair, unfortunately many proposed risk factors lack biological plausibility. This thesis reports a mixed methods approach to analyse risk factors for AT development. A Delphi study (using world tendon experts) was used to develop a consensus on risk factors for AT which were then used in an epidemiological study of UK runners – a high risk group for tendinopathy who have not previously been examined. Plantarflexor strength was identified as a potential contributor in AT development and this led to the development of a theory on why current treatment modalities work. This was further examined using a systematic review to determine whether changes occur in the muscle or tendon with the most common rehabilitation method (eccentric exercise). This review highlighted evidence for changes in plantaflexor power, amongst other factors. These findings were used to inform two studies examining how plantarflexor power was affected by AT and ultimately how rehabilitation altered these elements. The thesis reports multiple novel findings related to risk factors, the mechanism by which eccentric exercise may work, the effect of AT on plantarflexor function and how rehabilitation affects these deficits. The experimental studies contained in this thesis are some of the largest studies in the area, these studies identify significant torque and endurance deficits of the plantarflexors highlighting that Soleus appears to be most affected, whilst the later study reported how an eccentric rehabilitation regime improved these deficits but failed to fully resolve them. This offers an important clinical target but also highlights that rehabilitation needs to be for a longer duration with further modifications to resolve these identified plantarflexor deficits.