MRI for Tennis Elbow (Lateral Epicondylitis)

What Is Tennis Elbow?

Tennis elbow (lateral epicondylitis) is a painful condition affecting the tendons that attach to the bony prominence on the outside of the elbow — the lateral epicondyle. Despite its name, most people with tennis elbow have never picked up a racquet. It's caused by repetitive gripping, twisting, and lifting movements that strain the common extensor tendon origin, particularly the extensor carpi radialis brevis (ECRB) tendon.

The term "epicondylitis" implies inflammation, but microscopic studies consistently show that the underlying problem is tendon degeneration (tendinosis or tendinopathy) rather than active inflammation — disorganised collagen fibres, increased ground substance, and neovascularisation (new blood vessel growth) without inflammatory cells.

Tennis elbow affects approximately 1-3% of the general population, with peak incidence between ages 35 and 55. It's equally common in men and women. The dominant arm is affected in about 75% of cases. Occupational risk factors include plumbing, carpentry, bricklaying, computer work with a mouse, and any job involving repetitive wrist extension or gripping. In tennis players specifically, it's associated with poor backhand technique and inappropriate racquet grip size.

Why MRI Is Used for Tennis Elbow

Tennis elbow is overwhelmingly a clinical diagnosis. Physical examination — tenderness over the lateral epicondyle, pain with resisted wrist extension and middle finger extension, and pain with gripping — is sufficient for most cases. MRI enters the picture in specific situations:

• Failed conservative treatment: If symptoms persist beyond 6-12 months despite physiotherapy, splinting, and injections, MRI helps determine whether there's a structural tear requiring surgery.
• Atypical presentation: Symptoms that don't fit classic tennis elbow — radiating pain, locking, instability, or neurological symptoms — warrant MRI to exclude other diagnoses.
• Pre-surgical assessment: Before any surgical intervention (open or arthroscopic debridement), the surgeon needs to know the exact extent of tendon damage, whether there's a partial or complete tear, and whether other structures are involved.
• Assessing other pathology: MRI can simultaneously evaluate the lateral collateral ligament complex, the radial nerve, intra-articular pathology (loose bodies, plica, cartilage damage), and the posterior interosseous nerve — all potential causes of lateral elbow pain.
• Medico-legal or occupational health claims: Objective imaging evidence may be required to document the extent of tendon damage.

MRI Sequences Used

• T1-weighted coronal and axial: Shows normal tendon anatomy with excellent detail. The common extensor tendon origin appears as a low-signal (dark) band attaching to the lateral epicondyle. Any disruption or thinning is clearly visible.
• T2-weighted fat-saturated (or STIR) coronal, axial, and sagittal: The key diagnostic sequences. In tendinopathy, increased signal within the tendon indicates oedema, degeneration, or partial tearing. A complete tear appears as a full-thickness gap with surrounding fluid.
• Proton density (PD) fat-saturated: Provides excellent soft tissue contrast and is particularly useful for assessing the lateral collateral ligament complex and the articular cartilage of the radiocapitellar joint.
• Gradient echo sequences: Helpful for detecting loose bodies within the elbow joint.

What Radiologists Look For

• Common extensor tendon origin: The radiologist assesses the tendon for thickening (indicating chronic tendinopathy), increased T2 signal (oedema/degeneration), partial tearing (high-signal cleft within the tendon substance), or complete tear (full-thickness gap with retraction).
• ECRB tendon specifically: The ECRB is the most commonly affected tendon in tennis elbow. On axial images, it lies deep to the extensor digitorum communis (EDC). A tear may involve ECRB alone, ECRB and EDC, or rarely the entire common extensor origin.
• Tear grading: Partial tears are graded by depth: low-grade (less than one-third thickness), moderate (one-third to two-thirds), and high-grade (more than two-thirds). Full-thickness tears may involve retraction of the tendon edge.
• Lateral collateral ligament complex: The lateral ulnar collateral ligament (LUCL) is closely associated with the extensor origin and can be injured simultaneously. LUCL damage can cause posterolateral rotatory instability — a more complex problem than simple tendinopathy.
• Bone marrow oedema: Increased signal within the lateral epicondyle on T2/STIR sequences indicates bony reactive changes from chronic tendon traction — a common finding in severe tennis elbow.
• Radial nerve: The posterior interosseous nerve (deep branch of the radial nerve) passes close to the lateral epicondyle. Entrapment of this nerve (radial tunnel syndrome) can mimic tennis elbow. MRI may show denervation oedema in the supinator muscle if the nerve is compressed.
• Intra-articular findings: Radiocapitellar cartilage damage, loose bodies, synovial plica, and joint effusion — all potential contributors to lateral elbow pain that MRI can identify.

How to Prepare for the Scan

• No special preparation — eat and drink normally
• Remove watches, bracelets, and any elbow or wrist supports/splints
• Wear a short-sleeved top or one that can be easily rolled above the elbow
• If you can tolerate the position, the scan works best with the arm extended above the head — practice this briefly beforehand if you're unsure

What Happens During the Scan

Elbow MRI positioning varies between centres. The most common approaches are:

• Superman position: Lying prone (face down) with the affected arm extended above your head into the scanner. This gives the best image quality but can be uncomfortable for the shoulder.
• Arm by side: Lying on your back with your arm resting by your side. More comfortable but the elbow is further from the magnet's centre, which can reduce image quality.

A small surface coil wraps around your elbow. The scan takes approximately 25-35 minutes. Keeping your elbow still is important — even small movements can blur the tendon detail.

The scan is painless. If your elbow is very sore, the position may cause some aching, but you can communicate with the radiographer at any time if you need a brief break.

Contrast injection is not routinely used for tennis elbow assessment.

What MRI Can't Show

• Pain itself: MRI findings don't always correlate with symptoms. Studies have shown that a significant proportion of asymptomatic people have abnormal MRI signal in their common extensor tendon. Conversely, some patients with severe clinical tennis elbow have relatively modest MRI changes. The clinical picture matters as much as the scan.
• Dynamic instability: If posterolateral rotatory instability is suspected, MRI shows the static LUCL but may not demonstrate the instability that occurs during specific movements. Stress radiographs or examination under anaesthesia may be needed.
• Healing response: MRI changes lag behind clinical improvement. A tendon that looks abnormal on MRI may be functionally improving. Following up MRI too early after treatment can be misleading.
• Microscopic tendon changes: MRI can detect macroscopic tearing and signal changes, but the earliest stages of tendinopathy (disorganised collagen at the microscopic level) may be below MRI resolution.

Treatment Pathways After Diagnosis

• Physiotherapy with eccentric exercises: The Tyler Twist exercise and progressive tendon loading are the most evidence-based treatments. A structured programme over 6-12 weeks produces improvement in the majority of cases. This should be tried (or retried with specialist supervision) before considering surgical options.
• Activity modification and ergonomic assessment: Identifying and modifying the repetitive activities causing the problem. Ergonomic mouse, keyboard tray, and workstation assessment for office workers.
• Counterforce brace (tennis elbow strap): A strap worn just below the elbow distributes force away from the damaged tendon origin. Useful as an adjunct during activities.
• Corticosteroid injection: Provides short-term relief (4-6 weeks) but evidence shows it may delay long-term recovery. Current evidence generally discourages repeated steroid injections for tennis elbow.
• PRP (Platelet-Rich Plasma) injection: Growing evidence supports PRP for chronic tendinopathy unresponsive to physiotherapy. A blood sample is taken, processed to concentrate platelets, and injected into the tendon.
• Shockwave therapy (ESWT): NICE-approved for chronic tennis elbow. Typically a course of 3-5 treatments delivered weekly.
• Surgery: Reserved for cases failing 6-12 months of conservative management. Options include open or arthroscopic debridement of the degenerate tendon tissue, with or without repair. MRI guides the surgical approach by mapping the exact location and extent of the tear. Recovery takes 3-6 months.

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