Lateral Epicondylitis (Tennis Elbow)

Lateral epicondylitis, tennis elbow, is a degenerative condition of the common extensor origin at the lateral epicondyle of the humerus. The name misleads twice over: only 5-10% of patients play tennis, and the "-itis" promises an inflammation that histology does not support. It is a tendinosis, not a tendinitis.

Who. The annual incidence is 1-3% of the general population, peaking at 35-50 years, the years of heaviest occupational demand. The dominant arm is affected in 75% of cases, and the typical patient is a manual worker, a computer user or a racquet-sports player.

Risk factors.

• Repetitive wrist extension and supination
• Manual labour: mechanics, carpenters, painters
• Computer work with poor ergonomics
• Racquet sports, especially with poor technique
• Smoking, which impairs tendon healing
• Diabetes, through its association with tendinopathy

Natural history and impact. The condition is self-limiting in most cases and resolves within 12-18 months, but it becomes chronic in 10-20%. While it lasts it hurts with lifting and gripping, keeps manual workers in particular off work, and carries an economic burden of lost working days and treatment costs.

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The common extensor origin. The lateral epicondyle is the attachment for four muscles, and their involvement is far from equal.

The lesion. It sits on the undersurface of the ECRB at its origin, Nirschl's original observation. That surface takes the maximum tensile stress and has a relatively poor blood supply, and the tissue found there is grey, friable and without normal tendon architecture: angiofibroblastic hyperplasia, the "Nirschl lesion".

How the load arrives. The ECRB origin is stressed most during wrist extension with the elbow extended, and pronation increases its tension. Eccentric loading in the deceleration phase of a tennis backhand or a hammer swing, repeated, causes cumulative microtrauma, and the healing response fails because the tendon-bone interface is poorly vascularised.

The degenerative cascade. The tendon passes through recognisable stages.

Histology. Fibroblasts are increased, without significant inflammatory cells. The collagen is disorganised type III where type I should be, there is neovascularisation with accompanying nerve ingrowth, and the pain mediators substance P and glutamate are increased. Prostaglandins are absent, which explains the poor response to NSAIDs.

The nerve. The posterior interosseous nerve lies deep to the common extensor origin and, about 4-5cm distal to the lateral epicondyle, passes deep to supinator at the level of the radial neck. That position matters twice: compression of the nerve can coexist with lateral epicondylitis and mimic it, and the nerve is at risk during surgical release. Telling the two conditions apart is critical, and the clinical distinction is set out with the assessment below.

History. Pain over the lateral elbow, radiating into the forearm, that came on gradually with overuse; an acute onset after a single event is rare. Gripping, lifting and wrist extension aggravate it, rest relieves it, and patients describe trouble with the cup or kettle, a handshake or a doorknob. Ask about occupation (manual labour, computer work, typing), sport (tennis, golf and other racquet sports, and their technique), which hand is dominant, how long it has lasted (weeks against months), and what has been tried, injections included. Severe pain at rest or night pain is a red flag for other pathology.

Examination. Inspection is usually normal, with no swelling or deformity; marked swelling points to something else, septic arthritis or a fracture. The most reliable finding is tenderness 1cm distal and anterior to the lateral epicondyle, at the ECRB origin. Elbow flexion and extension and forearm rotation are full, and a reduced range suggests intra-articular pathology.

Provocative tests. Cozen's is the gold standard; pain is reproduced by resisted wrist extension and by resisted supination.

Why Cozen's works. Resisted wrist extension loads the ECRB maximally and reproduces the pain at its origin. The test is most sensitive with the elbow fully extended, which increases tension on ECRB, and the wrist radially deviated, ECRB's primary action. Mill's test stretches the tendon rather than loading it.

What it is. A synovial plica is a normal fold of the joint lining at the posterolateral or posterior radiocapitellar joint. With repetitive pronation-supination it can thicken, become fibrotic and impinge between the radial head and capitellum, and a symptomatic plica is a recognised cause of recalcitrant or "failed" tennis elbow.

When to suspect it. Lateral elbow pain accompanied by clicking, snapping or catching on rotation; tenderness over the radiocapitellar joint, slightly posterior to the epicondyle, rather than at the ECRB origin; or an apparent tennis elbow that fails to settle. This is one reason the arthroscopic approach is valued: the surgeon can inspect and resect a symptomatic plica at the same sitting. Radial tunnel syndrome (pain further distal) and posterolateral rotatory instability (a history of giving way) have their own pathways.

Lateral epicondylitis is a clinical diagnosis, made on a history of overuse and gradual onset and on lateral epicondyle tenderness with a positive Cozen's or Mill's test. Imaging is not required to make it; it is used to exclude other pathology or to plan surgery.

Radiographs. AP and lateral views are usually normal, and calcification is a rare finding in chronic cases. Their purpose is to exclude arthritis, loose bodies, fracture and osteochondritis dissecans.

Ultrasound. When the diagnosis is uncertain, a dynamic examination can show tendon thickening, hypoechoic areas of degeneration and neovascularisation on Doppler. It is cost-effective and can guide injections, but it is operator-dependent and cannot assess intra-articular pathology.

MRI. T1 and T2 sequences show increased signal at the ECRB origin, partial tears and bone marrow oedema. It is indicated after failed conservative treatment, for surgical planning, and to exclude other causes such as radiocapitellar arthritis or an osteochondral lesion; it is not routinely required.

EMG and nerve conduction studies. These are for the patient whose motor weakness raises PIN syndrome, or to exclude cervical radiculopathy: weakness of finger or thumb extension, pain distal to the lateral epicondyle and atypical symptoms are the indications. In pure radial tunnel syndrome, pain without weakness, the studies are usually normal, so a normal EMG does not exclude it and the diagnosis remains clinical.

Why eccentric loading. Because the lesion is a failed-healing tendinosis, anti-inflammatory measures only mask symptoms. Controlled eccentric exercise, lengthening under load, applies a mechanotransduction stimulus that drives tenocyte collagen synthesis, remodels the disorganised type III collagen toward organised type I, reduces the neovascularity and its accompanying nerve ingrowth, and progressively restores the tendon's load capacity. It treats the actual pathology.

Why it is the backbone. Eccentric protocols outperform standard concentric exercise for lateral epicondylosis, and they are the single most important evidence-based conservative measure and the backbone of the conservative trial that precedes any surgery.

Pitfalls. Whichever technique is used:

• Do not detach the entire common extensor origin; preserve normal tendon anterior and posterior
• Do not release the lateral collateral ligament, which lies posterior to ECRB and is essential for elbow stability
• Do not debride too deep; the joint capsule and the PIN lie beneath
• Do not tension the repair; the wrist stays neutral to avoid re-rupture
• Do not immobilise for long; early motion prevents stiffness

Recurrent pain after surgery. The causes are inadequate debridement of the pathological tissue, coexisting pathology that was never addressed (PIN compression, radial tunnel syndrome, a plica), poor rehabilitation compliance, and a return to provocative activities too soon. Reassess the diagnosis with MRI, and with EMG if PIN compression is suspected; trial injection therapy; and revise only for clear residual ECRB pathology.

PIN injury. The nerve is at risk during deep dissection through supinator, arthroscopic debridement (especially from the mid-anterolateral portal) and excessive retraction with the forearm pronated, so limit the depth of dissection to superficial to the joint capsule, and identify and protect the nerve if it is encountered. Injury presents as weakness of finger and thumb extension with no sensory loss; it is usually a temporary neuropraxia.

Stiffness. The risk rises with immobilisation beyond 2 weeks, extensive capsular damage and, rarely, heterotopic ossification. Prevent it with an early motion protocol in a hinged elbow brace that allows movement, and avoid rigid splinting.

The principle. Begin gentle active motion within the first week, from day 5-7: the repaired ECRB is secure enough to tolerate motion, though not gripping, and prolonged immobilisation leads to a stiffness that is harder to treat than the original condition. Loading is then gradual, with eccentric work from 6 weeks, progressive resistance and no pain with exercise. Patients should expect 3-6 months to full recovery, and a gradual rather than premature return to work and sport.

Red flags after surgery.

• Increasing pain: infection or re-injury
• Weakness: PIN injury
• Severe stiffness: needs aggressive therapy
• No improvement by 3 months: consider revision

After conservative treatment. The 80-90% who improve with structured rehabilitation (eccentric exercises, bracing, activity modification) do so within 12 months, and the natural history is self-limiting regardless of treatment.

After surgery. Open and arthroscopic release have similar success rates; the difference between them is speed of return, and the complications are mostly minor.

Predictors of a poor outcome. On the patient's side:

• Workers' compensation claim
• Secondary gain issues
• Poor rehabilitation compliance
• Smoking, which impairs healing

And on the surgeon's:

• Inadequate debridement, with grey tissue left behind
• Damage to the LCL, causing instability
• PIN injury, causing weakness
• Prolonged immobilisation, causing stiffness
• Early return to activity, causing re-injury

The six-month rule. Patients who undergo surgery after less than 6 months of conservative treatment have worse outcomes than those who complete an adequate trial. The reasons are multifactorial: the natural history means many would have improved anyway; the patient may not be fully committed to recovery; the rehabilitation attempt was inadequate; and the group is selected for more demanding patients. Always complete 6-12 months of conservative treatment before considering surgery.

Global epidemiology (source-cited):

Major guidelines and evidence syntheses, side by side:

Practice variation by setting:

Return-to-work principles (any setting):

• Manual workers often need extended time off (3-4 months after open release)
• Ergonomic assessment and graduated return with modified duties
• Occupational therapy input where available