Tennis elbow has one of the highest treatment failure rates in common musculoskeletal practice. Physiotherapy, cortisone injection, extracorporeal shockwave therapy, and platelet-rich plasma injection are all applied to the lateral epicondyle and the extensor tendon origin, all targeting the same location, and all producing the same disappointing long-term outcomes in a significant proportion of patients. The reason is that the lateral epicondyle is where the pain is, not where the problem is. The problem is neurological, and it is upstream.
Lateral epicondylitis is a good example of the inadequacy of the condition-based approach to a clinical problem. Nowhere in the literature does anyone attempt to identify the physiologic differences in those people who get tennis elbow and those who don’t, given the same workload. The cause is never identified so the treatments are generic, random and usually of minimal effect. Only when a cause is identified can effective long-term treatment be rendered, and the cause (and therefore treatment) may differ between individuals.
Afferentology approaches lateral epicondylitis with a prior question: why are the wrist extensor muscles failing to absorb the forces that are accumulating at their tendon origin? The extensor carpi radialis longus, extensor carpi radialis brevis, extensor digitorum, and extensor carpi ulnaris are the muscles that attach at or near the lateral epicondyle. Under normal neurological conditions, these muscles absorb the tensile forces generated during grip and wrist extension through active, controlled contraction. When they are inhibited or overfacilitated the tendon absorbs the force the muscle should have managed. The muscle is not weak because it is injured. The tendon is injured because the muscle is neurologically inhibited or overly stimulated.
The Wrist Extensors: Motor Neuron Supply and the Cost of Inhibition
The wrist and finger extensors are supplied by the radial nerve, which derives primarily from C6, C7, and C8. Their tone is maintained by the myotatic reflex at these cord levels. During gripping and wrist extension the wrist extensors should be controlling force eccentrically, absorbing the load that passes through the wrist and transmitting it to the forearm musculature. When the motor neuron output to these muscles is reduced, the eccentric load capacity is compromised. The tendon at the lateral epicondyle absorbs tensile forces beyond its design tolerance. Collagen degeneration follows. Imaging shows tendinosis. The treatment is directed at the tendinosis. The motor neuron failure that produced it continues unchallenged.
The patient who presents with tennis elbow that has not responded to three cortisone injections and six months of physiotherapy is, in almost every case, a patient whose extensor motor neuron supply has not been tested properly. The muscle appears to function normally on cursory examination. Standard strength testing of the wrist extensors measures the output of a compromised system and identifies weakness — which is then treated with eccentric loading. Eccentric loading into a neurologically inhibited muscle group is force application at a tendon origin that cannot be protected by the muscles attached to it. Symptoms worsen, or return immediately when loading resumes.
"Tennis elbow is not a tendon problem. It is a motor neuron problem expressing at a tendon. The tendon is showing you where the force went when the muscle could not absorb it. The muscle could not absorb it because the software was not running."
What Is Driving the Inflammation
The afferent sources most commonly inhibiting the wrist extensor group in lateral epicondylitis are not at the elbow:
- Cervical disc afferents at C6-C7: The radial nerve's primary derivation from C6, C7 and C8 means that any withdrawal reflex activity at these cord levels directly compromises wrist extensor motor neuron output. A C6-C7 disc herniation or facet inflammation, even one producing no radicular arm symptoms, can inhibit the wrist extensors sufficiently to transfer load to the lateral epicondyle tendon origin. The patient presents with elbow pain and no neck symptoms. The disc is the source.
- Shoulder girdle inhibition: The rotator cuff muscles and shoulder stabilisers, when inhibited by their own withdrawal reflex patterns, alter the mechanics of the entire upper limb kinetic chain. A shoulder that cannot absorb load correctly transfers force distally, first to the elbow, then to the wrist. A patient with tennis elbow who also has demonstrable rotator cuff inhibition on PRT has a proximal source that is contributing to the distal tendon loading.
The Software Test: Protective Reflex Testing
PRT for lateral epicondylitis tests wrist flexion, wrist extension, finger extension and ulnar and radial deviation. It’s also important to test the pronators and supinators of the elbow in various degrees on elbow flexion. Weakness patterns give hints as to the location of the actual neurological insult which we then identify by changing the afferent input or proprioception and retesting to see if the strength has returned, or the overfacilitaftion is reversed.
This methodology of finding the weakness and then finding the correction is the underlying principle for the application of afferentology.
The clinical significance of this finding extends beyond symptom management. A patient with tennis elbow who achieves immediate wrist extensor tone restoration on PRT with a C6-C7 afferent challenge does not need a tendon intervention. They need their cervical afferentation addressed and fixed. The tendon will recover naturally when the muscle resumes its mechanical role. Prescribing eccentric loading before this restoration is asking the tendon to protect itself against forces it still cannot pass to the muscle.
Tennis elbow is not a local tissue problem. It is what happens when upstream software failure sends load to a tendon that cannot defend itself.
Find the motor neuron failure. Restore the wrist extensor tone. Then, and only then, load the system progressively. Until that sequence is followed, the tendon will continue to fail, and the treatment will continue to address the wrong problem.
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References- Lenoir, H., Mares, O., & Carlier, Y. (2019). Management of lateral epicondylitis. Orthopaedics & Traumatology: Surgery & Research, 105(8S), S241-S246.
- Alizadehkhaiyat, O., & Frostick, S. P. (2015). Electromyographic assessment of forearm muscle function in tennis players with and without lateral epicondylitis. Journal of Electromyography and Kinesiology, 25(6), 876-886.
- Nicholas Johns Vivek Shridhar (2020)Lateral epicondylitis: Current concepts Australian Journal of General Practice, 49, 707–709.