Further to the article recently published on wrist injuries, I’ve had some feedback on the issues that might also relate to other injuries. In the first article we talked more about injuries that might be occasioned due to a fall or brace - these usually involve the FLEXORS of the wrist. But what of the other side of the equation? The Wrist Extensors are also implicated in many movements and whilst we may use the flexors a little more for bracing and grip, the EXTENSORS can be implicated in a number of conditions that may be directly more related with wrist movement and mobilisation in the wrist.
The Extensors are a group of muscles that make up the bulk of the posterior forearm. They are separated into two distinct groups of superficial and deep muscles. We have talked before about the bulky Brachioradialis which is the primary elbow flexor and often mistaken as the lesser elbow flexor over Biceps Brachii. In this article we will look at the smaller muscles that can often be attributed to the dreaded Tennis Elbow. The superficial group is made up of Brachioradialis and Anconeus (elbow extensor) but there are a group of 4 Extensors that all insert into the common tendon at the lateral epicondyle and hence have a huge influence on the chronic conditions that are exacerbated by sports such as tennis and golf. In the case of the extensors, it is usually more related to tennis elbow due to the extensors common insertion at the lateral epicondyle of the humerus. Because these muscles all extend the wrist, some are also wrist adductors and everters. Looking at these 4 muscles in detail explains why small movements at the wrist and actions here have an effect on the this classic condition.
Superficial Layer
Extensor Carpi Radialis Longus (ECRL) and Brevis (ECRB) - extend and abduct the wrist. This pulls the wrist sideways towards the thumb so at the height of the golf swing, the tendency here can be to use too much wrist abduction and strain overuse the ECRL and ECRB.
Extensor Carpi Ulnaris - extends and adducts the wrist which pulls the wrist towards the 5th digit. As is always the way with muscles, the wrist adductors may be strained if there is too much abduction in an action. The interplay between these two muscles is important if you are involved in wrist movement as in the golfers swing or the tennis movement. It is indicated in constant adduction or abduction of the wrist which you would experience in say a heavy top spine action. This wrist movement combined with the impact of striking a ball repeatedly as well as wielding a racquet can create issues at the common insertion on the lateral epicondyle of the elbow.
Extensor Digitorum (Communis) - this is a lesser muscle of concern when looking at elbow issues and more an issue in digitising. So for people on keyboards, this muscle can become a problem. It extends to the 4 fingers and whilst it is a weak wrist extensor, its main function is to extend the fingers. So typists, pianists and those involved in fine digit movements, this muscle can become overused and cause irritation. It lies right in the middle of the superficial layer between ECRB/ECRL and Carpi Ulnaris.
Extensor Digiti Minimi - as the name suggests, is a small muscle that extends the 5th digit. In some people this muscle is fused with Extensor Digitorum. He also contributes to wrist extension.
All of the above muscles are all ennervated by the Radial Nerve and so all work together to enable wrist extension along with adducton/abduction and some general finger movement.
Deep Layer
The Deep layer consists of muscles that act mainly on the thumb and index finger excluding Supinator which is involved in supinating the forearm and rotating the ulna against the radius bone. It arises from the lateral epicondyle of the elbow and is a two headed muscle that wraps around the radius bone like a long sleeve inserting on the posterior thumb. The other muscles in this layer are all concerned with abduction and extension of the thumb and index finger.
Abductor Pollicis Longus - the snuff box tendon. Pollicis relates to the thumb and the tendon of this muscle extends the thumb and creates the small divot on the dorsal palm that was used to place ‘snuff’ and sniff from in the 19th century. Its chief movement is to abduct the thumb (moving it towards the palm)
Extensor Pollicis Brevis - also contributes to the lateral border of the snuff box and extends the thumb (extending it away from the palm). It runs deep to Abductor Pollicis Longus.
Extensor Pollicis Longus - has a larger muscle belly that the Ext Pollicis Brevis and also extends the thumb but reaches to all the carpal joints of the thumb. EPL forms the medial border of the ‘snuff box’.
Extensor Indicis Proprius - extends the index finger and runs from the ulna bone.
All these finer muscles are involved in digital movement and the particular articulations of the thumb and forefinger which go a long way to distancing us evolutionally from our Ape counterparts. Our grip and opposing thumb movement has enabled us to develop our tactile use of the hand and the world around us. These deeper muscles with the exception of Supinator all orginiate from the ulna bone itself and thus are involved in much finer movements of the hand and fingers and don’t relate as much to our investigation here for chronic elbow and wrist pain -but they can play a role in how we use our wrist and elbow.
In understanding these muscles and their particularity, we can begin to understand the role each one plays alongside the other muscles that act on elbow flexion such as Brachioradialis, Biceps Brachii, Anconeus and triceps. In terms of chronic issues such as tennis and even golfers elbow. With both of these articles we have touched on the degenerative changes that can occur with chronic irritation of the tendinous insertions from excessive movement which can be exacerbated by sports movements but just as easily from over extension and over flexion at the wrist.
Remembering that the arm is a chain and the wrist and elbow are two distinct joints that play various roles in stability and movement. The wrist is highly articulate and moveable and the elbow is the moving junction between the shoulder and the wrist and when there is instability in either the wrist or the shoulder, often it is the elbow that is left to deal with the compensation. Strengthening our wrists in both flexion and extension is highly encouraged and it has to be said that often gymnasts are the ones who do the best in the field of mobility and strength in the wrists… but that’s another blog.
Stay tuned for more info on wrist stability, exercises and strength.
