# Lateral and Medial Epicondylopathy

## Anatomy

### Lateral Epicondyle
Origin of the common extensor tendon. **Extensor carpi radialis brevis (ECRB)**: most commonly affected tendon in lateral epicondylopathy. Other muscles: extensor digitorum communis, extensor carpi ulnaris, extensor digiti minimi. Extensor carpi radialis longus originates just proximal to the lateral epicondyle on the supracondylar ridge. The lateral ulnar collateral ligament (LUCL) also originates near the lateral epicondyle.

### Medial Epicondyle
Origin of the common flexor-pronator tendon. **Flexor carpi radialis** and **pronator teres**: most commonly affected. Other muscles: palmaris longus, flexor digitorum superficialis, flexor carpi ulnaris. The ulnar collateral ligament (UCL/medial collateral ligament) originates from the medial epicondyle. The ulnar nerve runs in the cubital tunnel posterior to the medial epicondyle.

### Neurovascular Considerations
**Posterior interosseous nerve (PIN)**: deep branch of radial nerve; passes through the arcade of Frohse in the supinator muscle, 2-3 cm distal to the lateral epicondyle. **Radial tunnel**: space between the radial head and supinator where the PIN can be compressed. **Ulnar nerve**: vulnerable at the cubital tunnel; may be co-involved with medial epicondylopathy.

## Pathophysiology

### Tendinopathy Model (Not Tendinitis)
The term "epicondylitis" is a misnomer -- histopathology shows degenerative tendinopathy, not inflammation. Key histological findings: angiofibroblastic hyperplasia (Nirschl). Disorganized collagen fibers. Increased ground substance.

Neovascularization without inflammatory cells. Fibroblast proliferation. The tendinopathy continuum (Cook and Purdam model): 1. **Reactive tendinopathy**: non-inflammatory cell response to acute overload; reversible.

2. **Tendon dysrepair**: failed healing with matrix disorganization. 3. **Degenerative tendinopathy**: cell death, irreversible structural change, areas of acellularity.

### Biomechanics of Injury
**Lateral epicondylopathy**: repetitive wrist extension and forearm supination/pronation; eccentric loading of ECRB during gripping activities. **Medial epicondylopathy**: repetitive wrist flexion and forearm pronation; valgus stress (overhead throwing, golf). Cumulative microtrauma exceeds tendon repair capacity.

## Epidemiology
Lateral epicondylopathy is 5-10 times more common than medial. Peak incidence: 40-50 years old. Affects 1-3% of the general population annually. Dominant arm affected in 75% of cases.

Occupational risk factors: repetitive manual work, forceful gripping, keyboard use. Sports: tennis (lateral), golf/throwing sports (medial).

## Clinical Evaluation

### Lateral Epicondylopathy

#### History
Gradual onset of lateral elbow pain. Pain with gripping, turning doorknobs, lifting with palm down. May radiate into the forearm extensors. Typically no numbness or tingling (if present, consider radial tunnel syndrome).

#### Physical Examination
Point tenderness at or just distal to the lateral epicondyle (ECRB origin). Pain with resisted wrist extension (elbow extended, forearm pronated). Pain with resisted middle finger extension (Maudsley test) -- more specific for ECRB. Pain with passive wrist flexion with elbow extended (stretches extensors).

Grip strength often reduced. Cozen test: resisted wrist extension with elbow at 90 degrees flexion and forearm pronated. Mill test: passive pronation and wrist flexion with elbow extended reproduces pain.

### Medial Epicondylopathy

#### History
Gradual onset of medial elbow pain. Pain with gripping, wrist flexion activities. May have associated ulnar nerve symptoms (40% have coexisting ulnar neuropathy).

#### Physical Examination
Point tenderness at or just distal to the medial epicondyle. Pain with resisted wrist flexion and pronation. Pain with passive wrist extension (stretches flexor-pronator mass). **Always assess the ulnar nerve**: Tinel sign at cubital tunnel, elbow flexion compression test. **Always assess UCL stability**: valgus stress test, moving valgus stress test (in athletes).

### Differential Diagnosis

#### Lateral Elbow Pain
Radial tunnel syndrome (PIN compression): tenderness 3-4 cm distal to the lateral epicondyle, pain with resisted supination, rule of nine test. Posterolateral rotatory instability (PLRI). Radiocapitellar plica. Radiocapitellar arthritis. C6 radiculopathy. Referred pain from cervical spine.

#### Medial Elbow Pain
Ulnar neuropathy at the elbow (cubital tunnel syndrome). UCL insufficiency (especially in throwers). Medial elbow arthritis. C8-T1 radiculopathy. Referred pain from cervical spine.

### Imaging
**Radiographs**: usually normal; may show calcification at the epicondyle in chronic cases. **Ultrasound**: thickened, hypoechoic tendon; partial tears; neovascularization on Doppler; intrasubstance tears. **MRI**: reserved for refractory cases or when considering surgical intervention; shows tendon signal change, partial or complete tears. **Electrodiagnostic studies**: when radial tunnel syndrome or ulnar neuropathy is suspected.

## Management

### Conservative (Effective in 80-95% Over 12 Months)

#### Activity Modification and Education
Identify and modify provocative activities. Ergonomic assessment for occupational contributors. Counterforce brace (proximal forearm strap): reduces load on the tendon origin. Wrist extension splint for night use in severe cases.

#### Rehabilitation -- The Cornerstone of Treatment
**Eccentric exercise program** (strongest evidence): Tyler Twist with FlexBar for lateral epicondylopathy. Eccentric wrist extension: slow lowering of weight with forearm pronated over table edge. 3 sets of 15 repetitions, twice daily, for minimum 6-12 weeks.

Expect initial increase in pain before improvement. **Stretching**: wrist flexion stretches (lateral), wrist extension stretches (medial). **Isometric loading**: may be beneficial in the reactive stage for pain reduction. **Grip strengthening**: progressive, pain-guided. **Kinetic chain**: assess and address proximal weakness (shoulder/scapular stabilizers), core strength.

#### Pharmacologic
Topical NSAIDs (diclofenac gel): modest benefit with lower systemic risk. Oral NSAIDs: short-term pain relief, no disease-modifying effect. Topical nitroglycerin patches: some evidence for chronic tendinopathy (nitric oxide donor theory).

#### Injections
**Corticosteroid injection**: short-term pain relief (2-6 weeks), BUT evidence of worse long-term outcomes compared to wait-and-see (Coombes et al., 2010). Corticosteroid may inhibit tendon healing and cause recurrence. Use judiciously: only for severe pain interfering with rehabilitation. **PRP injection**: mixed evidence; some studies show benefit over corticosteroid at 6-12 months, but large trials (RESTORE, Mishra et al.) show inconsistent results.

**Autologous blood injection**: limited evidence, similar proposed mechanism to PRP. **Botulinum toxin injection**: to common extensor origin reduces tendon loading; risk of temporary finger extension weakness; limited evidence. **Prolotherapy (hypertonic dextrose)**: emerging evidence, proposed mechanism of stimulating healing response.

| Injection Type | Short-Term Efficacy | Long-Term Outcome | Key Concern |
|---------------|--------------------|--------------------|-------------|
| Corticosteroid | Good (2-6 weeks) | Worse than wait-and-see at 1 year | Inhibits tendon healing, higher recurrence |
| PRP | Moderate | Possible benefit at 6-12 months | Inconsistent trial results; cost |
| Autologous blood | Limited evidence | Unknown | Similar mechanism to PRP |
| Botulinum toxin | Moderate | Limited evidence | Temporary finger extension weakness |
| Prolotherapy (dextrose) | Emerging | Emerging | Proposed healing stimulation |

#### Other Modalities
Extracorporeal shockwave therapy (ESWT): moderate evidence for chronic lateral epicondylopathy. Acupuncture: short-term pain relief; insufficient evidence for long-term benefit. Low-level laser therapy: some evidence for short-term improvement.

### Surgical Management
Reserved for refractory cases failing 6-12 months of comprehensive conservative treatment. **Open or arthroscopic debridement** of degenerative tissue (Nirschl procedure). **TENEX (percutaneous tenotomy)**: ultrasonic debridement of pathologic tissue. Post-surgical rehabilitation: progressive ROM, gradual eccentric loading, return to activity at 3-6 months.

<image>Anterior view of the elbow joint showing the lateral epicondyle with the common extensor tendon origin (ECRB highlighted in red as the most commonly affected), and the medial epicondyle with the common flexor-pronator tendon origin (flexor carpi radialis and pronator teres highlighted). Show the ulnar nerve passing posterior to the medial epicondyle through the cubital tunnel, and the posterior interosseous nerve passing through the arcade of Frohse in the supinator muscle distal to the lateral epicondyle.</image>

<image>Illustration demonstrating the eccentric exercise protocol for lateral epicondylopathy using a FlexBar (Tyler Twist): Step 1 shows maximal wrist extension of the affected side gripping the bar; Step 2 shows both hands gripping with the bar twisted; Step 3 shows slow eccentric release with wrist flexion of the affected side. Include arrows showing direction of movement and labels for each step.</image>

<image>Ultrasound image illustration showing a longitudinal view of the common extensor tendon at the lateral epicondyle comparing a normal tendon (uniform fibrillar echotexture, normal thickness) with a tendinopathic tendon (thickened, hypoechoic, loss of fibrillar pattern, with small intrasubstance tear shown as an anechoic cleft). Label the lateral epicondyle, radial head, and tendon in both images.</image>

## Clinical Pearls

The natural history of lateral epicondylopathy is self-limiting in 80-90% of cases within 12-18 months even without treatment -- this informs shared decision-making. Corticosteroid injections provide short-term relief but are associated with higher recurrence rates and worse outcomes at 1 year compared to wait-and-see approaches. Always examine the cervical spine and ulnar nerve in patients presenting with medial elbow pain -- coexisting pathology is common. The Tyler Twist with a FlexBar is an inexpensive, evidence-based home exercise with demonstrated efficacy in RCTs.

Radial tunnel syndrome and lateral epicondylopathy frequently coexist; point of maximal tenderness helps differentiate (at vs. distal to the epicondyle). Tendinopathy is a degenerative process, not inflammatory -- treatments should aim to stimulate healing rather than suppress inflammation. Counterforce bracing provides functional improvement and can be used during activities even as patients progress through their exercise program. In athletes, address biomechanical factors: racquet grip size, stroke technique (tennis), throwing mechanics (baseball/overhead sports).

## References

- Coombes BK, Bisset L, Vicenzino B. Efficacy and safety of corticosteroid injections and other injections for management of tendinopathy: a systematic review of randomised controlled trials. *Lancet*. 2010;376(9754):1751-1767.
- Bisset L, et al. Mobilisation with movement and exercise, corticosteroid injection, or wait and see for tennis elbow: randomised trial. *BMJ*. 2006;333(7575):939.
- Tyler TF, Thomas GC, Nicholas SJ, McHugh MP. Addition of isolated wrist extensor eccentric exercise to standard treatment for chronic lateral epicondylosis: a prospective randomized trial. *J Shoulder Elbow Surg*. 2010;19(6):917-922.
- Nirschl RP, Pettrone FA. Tennis elbow: the surgical treatment of lateral epicondylitis. *J Bone Joint Surg Am*. 1979;61(6A):832-839.
- Cook JL, Purdam CR. Is tendon pathology a continuum? A pathology model to explain the clinical presentation of load-induced tendinopathy. *Br J Sports Med*. 2009;43(6):409-416.