Welcome back to the series of articles about physiotherapy and tennis elbow (also known as lateral epicondylitis, lateral epicondylosis and lateral epicondylalgia). So far we have covered who is affected by tennis elbow, the anatomy of the elbow and which muscles or tendons are most likely to be injured. This article will try to give an overview of a huge subject: the physiology of tendons and why they get injured, now this is a massive topic in physiotherapy and has been the subject of huge amounts of research (and in fact our knowledge on this topic is still developing) so I will only be touching the surface.

Forearm extensor muscles

Forearm extensor muscles

Firstly we need to look at what tendons actually are and why they might get injured in tennis elbow. Simply put a tendon is a piece of connective tissue that joins muscle to bone and is comprised of well organised mostly one directional collagen fibres (Wang et al 2003). Unlike muscles tendons can not contract themselves and are relatively inelastic (with a much lower proportion of elastin – only about 1-2% Jozsa & Kannus 1997). So basically muscles do the contraction and force generation but tendons, because they connect to the bones and are relatively inelastic, transfer that force over to the bones and move our joints. A key fact about tendons is that they generally will have a much lower blood supply than muscles and in turn have a lower metabolic rate which affects their ability to heal and makes an injury to a tendon much slower to recover and heal properly (Abate et al 2009). Furthermore the point at which muscle turns into tendon (the musculo-tendinous junction) is the point which is most often injured and is subject to large mechanical forces (Abate et al 2009).

Okay – how does this affect tennis elbow? Well, as we found out in the last article, extensor carpi radialis brevis (ECRB) is the most commonly injured muscle in tennis elbow and this muscle is most commonly injured at either the musculo-tendinous junction or at the lateral epicondyle (bony bit of the elbow) where the common extensor tendon inserts into the bone. Therefore understanding tendons and how they react and function is key to understanding tennis elbow.

Tennis Elbow

Tennis Elbow


The common extensor tendon as shown above is the continuation of all the extensors of the wrist and fingers and therefore any time you extend your wrist or your fingers to pick anything up it is put under stress. So it isn’t really a surprise that if you do too much of anything like picking things up then this tendon may get irritated and sore and that your physiotherapist will be able to find fairly easily a very sore spot on the lateral epicondyle of your elbow.

Next blog post will look in more detail at the physiology of what happens when the tendon gets injured in tennis elbow and hopefully manage to summarise and simplify decades of research on tendinopathies.


Abate M., Gravare-Silbernagel K., Siljeholm C., Di Iorio A., De Amicis D., Salini V., Werner S., Paganelli R. (2009) Pathogenesis of tendinopathies: inflammation or degeneration? Arthritis Research and Therapy 11 (3): 235

Jozsa, L., and Kannus, P., Human Tendons: Anatomy, Physiology, and Pathology. Human Kinetics: Champaign, IL, 1997

Wang J., Jia F., Yang G., Yang S., Campbell B., Stone D., Woo S., (2003) Cyclic Mechanical Stretching of Human Tendon Fibroblasts Increases the Production of Prostaglandin E2 and Levels of Cyclooxygenase Expression: A Novel In Vitro Model Study Connective Tissue Research 44: 128 – 133


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