Tennis Elbow Differential Diagnosis and Treatment:
While tennis elbow is by far the most common diagnosis of musculoskeletal pain on the lateral elbow, our clinic frequently sees patients with ongoing “chronic” lateral elbow pain which has not settled down with standard physiotherapy targeted at the diagnosis of “Tennis Elbow”.  If your management is not working, perhaps the differential diagnoses need to be considered?
There are a heap of differentials at the lateral elbow, most of them not so common:
•Tendon •Common extensor tendinopathy aka lateral epicondylalgia aka tennis elbow
•Nerve •Radial tunnel syndrome
•Posterior interosseous nerve syndrome
•C5 radiculopathy
•Nerve lesion superficial radial nerve
•Ligament •Lateral collateral ligament strain (Lateral ulnar collateral ligament, radial collateral ligament)
•Annular ligament
•Joint •Posterolateral plica
•Radiocapitular osteoarthritis
•Radial head subluxation
•Radiohumeral synovitis
•Bone •Fracture lateral epicondyle, radial head, olecranon
•Osteochondritis dissecans
•Generalised inflammatory condition
•Somatic referral proximal shoulder and neck structures
When discussing “Tennis Elbow” in this context, I am considering the pathology of Lateral Epicondylalgia (including Common Extensor Tendinopathy). I apologise for the use of inverted commas, but I struggle with the term “Tennis Elbow” as it does not tell me anything about my patient’s diagnosis, pathology or management plan.  I will continue to use the label of Lateral Epicondylalgia as it covers the diagnosis of Common Extensor Tendinopathy in absence of confirmed changes on imaging.
It seems that the most common differential diagnosis we encounter in clinical practice for those patients who have not improved with a good “Lateral Epicondylalgia” rehab programme is Radial Tunnel Syndrome (and Posterior Interosseous Nerve Syndrome).  The area of pain is quite similar, but the examination of this condition yields differing results.  If you would like to read further on Radial Tunnel Syndrome and Posterior Interosseous Nerve Syndrome then please refer to my blog for evidence based information regarding the pathophysiology and diagnosis of this condition.
Lateral Epicondylalgia
Commonly people with “Lateral epicondylalgia” report point pain over lateral elbow (as the name suggests).  This may radiate down the dorsolateral forearm in some people. Usually the patient describes an insidious onset of lateral elbow pain related to increased activity that may include repetitive gripping, finger or wrist movements.  There are differing options for management in all of these patient groups (ie. you need to change the provocative activity that is relevant for the patient in front of you).  Someone with pain after repetitive mouse work (specifically scrolling), will need differing management compared to a carpenter who experiences pain with tool use (I suspect this is due to a different location of sensitivity/pathology within the common extensor tendon).
Most people would use a combination of some of the following tests to diagnose Lateral Epicondylalgia or “Tennis Elbow”:
•Tenderness on palpation over the lateral epicondyle (may radiate down dorsolateral forearm in people who report these symptoms) (Huisstede et al. 2006)
•Pain with resisted middle finger extension
•Pain with resisted wrist extension
•Passive elbow extension
•Grip strength weakness
•Mill’s test (Passive wrist flexion with radial deviation)
•Cozen’s test (Resisted wrist extension in a flexed position with palpation of lateral epicondyle)
There is a serious omission of one very important muscle which also attaches to the lateral epicondyle, the supinator muscle. Perhaps Radial Tunnel Syndrome (and Posterior Interosseous Nerve Syndrome) would not be missed so often if testing for radial nerve compression is part of your standard testing battery for Lateral Epicondylalgia?
Radial Tunnel Syndrome
The patient with Radial Tunnel Syndrome will report pain over the dorsolateral forearm and possibly the lateral epicondyle.  It is usually precipitated by repetitive pronation/supination loading of the upper limb, with elbow extended.  This is logical as elbow extension would unload the bicep muscle, which would otherwise assist in the supination movement, and hence overload the supinator muscle.  The vast majority of the patients we see with this loading pattern include cleaners, patient care assistants and factory line workers.
However it is not uncommon for patients to report symptoms that are exacerbated by heavy gripping activities with repetitive flexion/extension of the wrist or carrying heavy objects in a fully supinated position (especially if biceps and shoulder girdle is weak).  These types of patients are typically painters and some mothers who carry their new born in one arm (or with concurrent DeQuervain’s tendinopathy resulting in radial nerve irritation).  Similarly they may present with a pre-morbid neural tissue disorder at the cervical spine, wrist or hand, which surfaces as a “double crush syndrome” once the radial nerve around the elbow is involved.
With these patients, treatment should be aimed at changing their provocative activities and loading patterns, just as you do for any other musculoskeletal condition.
There is a large gap in the research relating to the clinical examination of a patient with Radial Tunnel Syndrome, however I have listed the clinical tests we frequently use to diagnose this condition:
•Tenderness on palpation over the leading edge of supinator (~3cm distal and posterior to the lateral epicondyle) that is greater than at the lateral epicondyle (Lutz 1991, Hsu et al. 2012)
•Provocation – Pain with resisted supination or gripping (in a combination of supination/pronation and elbow flexion/extension – specific to the functional complaint) (Dang and Rodner 2009)
•Radial nerve tissue provocation test (Upper Limb Tension Test 2b)
•Weakness – Grip strength weakness (in a combination of supination/pronation and elbow flexion/extension – specific to the functional complaint)
•Cervical spine screened for involvement with Spurling’s test if there is weakness or paraesthesia within the distribution of the superficial radial nerve (Bono et al. 2011)
When examining the patient, careful consideration must be given to the testing procedures in the context of the functional complaint, and the reproduction of the patient’s exact complaint with examination procedures that load the suspected tissue directly.  Considering the testing procedures above for Lateral Epicondylalgia, and that the provocative tasks are quite similar in both patient groups, perhaps your physical examination should always include at least some components of testing for Radial Tunnel Syndrome?
It seems, more often than not, those with Radial Tunnel Syndrome will also have features of Lateral Epicondylalgia.  This is likely due to a few possibilities,
1.The Supinator has a slip of tissue at the lateral epicondyle,
2.Gripping activities involve the extensor tendons and therefore the lateral epicondyle,
3.Primary hyperalgesia related to the peripheral nerve branch serving the area,
4.Central sensitisation mechanisms (producing regional hyperalgesia) and
5.Poor specificity of the testing procedures.
The anatomy in the region is so interconnected, woven together, continuous and part of an integrated functional unit; what you see on any cadaver specimen or textbook has truly deconstructed the complexity of how the area functions with its environment.  Most people are aware these days that during a clinical examination of the shoulder, identifying a pathological structure has poor reliability in the current evidence base.  While I do advocate attempting to be as specific as possible with your diagnosis, I definitely don’t place as much weight on this compared to the considerations given to what modifies my patient’s complaint of pain.