Welcome back to the new series of articles about physiotherapy and common injuries and pathologies seen by physiotherapists. Last time we took a brief look at one of the most common musculo-skeletal conditions that a physiotherapist will encounter – tennis elbow (also known as lateral epicondylitis, lateral epicondylosis and lateral epicondylalgia). This article will now look at the anatomy of the elbow and the muscles connected to it in detail so that we can have a good idea of what is hurting or being injured in tennis elbow and can maybe start to have an idea of what causes it.
The elbow is an amazing piece of biomechanical design and is comprised of 3 bones – the humerus which is the upper arm bone and two bones in the forearm called the radius and ulna. The radius runs from the elbow to the thumb and the ulna starts at the bony prominence on the back of your elbow (olecranon process) and runs down to the wrist. To make it easy to remember which bone is which, when I was a student I used to repeat “the ulna is underneath the radius”. Simple I know but effective nonetheless when you are a physio student desperately trying to cram in your anatomical knowledge.
Now as we are looking at tennis elbow we are not going to look or worry too much about the actual elbow joint itself except to say that it has two ways of movement – flexion and extension (basically straightening and bending) and pronation and supination (pronation is rotating the hand palm down and supination palm up). It may seem strange that in a condition called tennis elbow we will be ignoring the elbow joint itself but hopefully the reason why will become clear soon.
The key part of the elbow in tennis elbow that we really need to examine is the lateral epicondyle – this is the point where all of the wrist extensors and finger extensors start from and is the point at which pain is felt in tennis elbow, it is also called the common extensor origin (for reasons which will become apparent soon) and is the site of attachment for the common extensor tendon. Pain here is the cardinal sign for tennis elbow that all physiotherapists look for.
Running from the lateral epicondyle and the common extensor origin are all of the muscles that extend the wrist and the fingers – extensor carpi radialis brevis, extensor carpi ulnaris, extensor digitorum, extensor indicis and extensor digiti minimi. Two other muscles have attachments at the lateral epicondyle – supinator and anconeus. All of these muscles merge together here to form what is known as the common extensor tendon which then attaches to the lateral epicondyle. So it is fairly obvious that this common extensor origin is an important point in wrist and finger extension and may well be a likely site of injury that physiotherapists will need to examine.
Before moving on it is worth considering the actions of a couple of these muscles in more detail extensor carpi radialis brevis and extensor carpi ulnaris have an important synergistic role in stabilising the wrist – they both act at the same time in concert with their flexor brothers (flexor carpi ulnaris and flexor carpi radialis) to prevent side to side movement at the wrist (ulnar and radial deviation). The two extensors also act together at the same time you grip an object to hold the wrist in extension a bit and prevent the finger flexors from flexing the wrist. In fact studies have shown that extensor carpi radialis brevis is the tendon most commonly injured in tennis elbow and the most common point that it is injured at is the common extensor tendon.
So hopefully from the above brief anatomy lesson we can now see that any extension or even flexion of the wrist is going to put a large amount of stress through the common extensor tendon and in turn if this tendon receives any injury we are likely to feel pain at the lateral epicondyle – which is where patients with tennis elbow will normally describe to their physiotherapist that they feel pain when they pick things up.
The next article will look at the physiology and some of the reasons why tendons get injured and why tennis elbow can often become chronic and last for a long time.