A recent article got me thinking about the subject of that bane of many runners Achilles tendonitis and why there is so little good quality research into its causes and treatment. There is a huge variety of treatments, including injections of all sorts of compounds into and around the tendon, blasting it with ultrasound, striping it from the surrounding tissues, scooping the centre out and making cuts in the tendon to name a few. Most of these have no rationale behind them and little or no evidence. What passes for research is usually very poor quality with small numbers of subjects, short follow up and lack of randomisation, there is reasonable evidence, at least in motivated individuals with tendonitis affecting the mid position of the Achilles tendon, a series of exercises when the tendon is stretched under tension (eccentric exercise) is effective. There is little evidence of how it might work but it seems to lengthen the tendon muscle unit, increases the tendon stiffness and increases the quantity of type 1 collagen.