Intersection syndrome

Overview

Intersection syndrome is a painful inflammatory condition affecting the forearm, specifically where two muscle groups intersect. It occurs at the crossover point of the first dorsal compartment (abductor pollicis longus and extensor pollicis brevis) and the second dorsal compartment (extensor carpi radialis longus and brevis) of the forearm. This overuse injury is commonly seen in athletes and individuals who perform repetitive wrist extension and thumb movements, such as rowers, weightlifters, and manual laborers. It is sometimes confused with De Quervain’s tenosynovitis but occurs more proximally on the forearm.

Causes

Intersection syndrome is primarily caused by repetitive friction and overuse at the intersection point of the forearm tendons. Key contributing factors include:

• Repetitive wrist and thumb motion: Especially activities involving extension and radial deviation.

• Overuse injuries: Common in rowers, skiers, weightlifters, and racket sport athletes.

• Improper technique: Using poor form during physical activity can increase strain on the forearm tendons.

• Sudden increase in activity: A rapid escalation in training intensity or volume without proper conditioning.

Symptoms

Symptoms of intersection syndrome typically develop gradually and may worsen with activity. Common signs include:

• Pain in the dorsal radial aspect of the forearm: Located approximately 4–6 cm above the wrist joint.

• Swelling: Noticeable at the site of tendon intersection.

• Crepitus: A squeaking or creaking sensation with wrist or thumb movement due to tendon friction.

• Tenderness: Pain on palpation over the affected area, especially during resisted wrist extension.

• Decreased grip strength or functional impairment: In severe or chronic cases.

Diagnosis

Diagnosis is typically clinical and based on history and physical examination. Additional tests may be used to confirm the diagnosis or rule out similar conditions:

• Physical exam: Reproduction of pain with resisted wrist extension or thumb movements, along with crepitus over the dorsal forearm.

• Ultrasound: Can show thickened tendons and confirm inflammation at the intersection point.

• MRI: Used in atypical or persistent cases to rule out other pathologies like tendon tears or De Quervain’s tenosynovitis.

• Differential diagnosis: Must distinguish from De Quervain’s tenosynovitis (which is located more distally near the base of the thumb) and radial nerve entrapment.

Treatment

Most cases of intersection syndrome respond well to conservative treatment aimed at reducing inflammation and allowing tendon healing:

• Rest: Discontinuation or modification of aggravating activities is essential.

• Ice therapy: Applying ice packs to reduce inflammation and pain.

• Nonsteroidal anti-inflammatory drugs (NSAIDs): To relieve pain and reduce swelling.

• Splinting: A wrist/thumb splint or brace may be used to immobilize the affected area and promote healing.

• Physical therapy: Focused on stretching, strengthening, and correcting biomechanics to prevent recurrence.

• Corticosteroid injections: May be considered in persistent or severe cases to reduce inflammation.

Prognosis

The prognosis for intersection syndrome is generally excellent with early and appropriate treatment. Most individuals recover fully within a few weeks to months. Delayed treatment or continued repetitive stress may lead to chronic pain or recurrence. Proper technique, gradual training progression, and ergonomic adjustments can help prevent future episodes. Surgical intervention is rarely needed and reserved for cases that do not respond to conservative therapy.