Pain in the carpus and forearm is a frequent reason for rheumatology consultation. Overuse tendonitis and repeated microtrauma are among the most frequent mechanical causes. De Quervain's tendonitis is one of the most common conditions, although there are also other less common disorders with a similar clinical presentation.

We present the case of a 28-year-old woman, with no clinical history of interest, who consulted due to the sudden onset of pain and swelling on the dorsal surface of the distal third of her right forearm with marked functional limitation on extension of the carpus and first finger. The patient is an administrative worker, whose only recent history of note was having rowed during her recent holidays. Examination revealed local heat and swelling on the dorsolateral region of the forearm around 5cm proximal to the radiocarpal joint. On resisted extension of the first finger, the patient's pain increased, and there was marked crepitus at this level. Finkelstein's manoeuvre was positive, painful at around 5cm proximal to the radiocarpal joint. Sensory examination was normal. The patient had no synovitis or pain in other areas.

An ultrasound was performed (Image 1) showing tenosynovitis of the 2 tendons of the I extensor compartment (short extensor and long abductor of the thumb) at the level of the distal third of the forearm as it crosses the tendons of the II dorsal compartment, with no power Doppler signal. Joint measurements of the AL+ECRL, and EB+ extensor tendons were taken, .38 and .41cm2 respectively, which are above the measurements usually described.1 There was no tendon involvement at the level of the radial styloid. Ultrasound of the carpus and forearm of the healthy side was normal. Distal intersection syndrome caused by rowing was diagnosed. The patient was treated with rest and immobilisation for a week, and ultrasound-guided injection of 40mg of triamcinolone acetonide. After 2 weeks she showed full clinical and ultrasound improvement.

Image 1.

Transverse ultrasound image of the distal region of the right forearm. Showing tenosynovitis (arrow) of the tendons of the I and II extensor compartment as they cross. AL: abductor longus of the first finger; EB: extensor brevis of the first finger; ECRB: extensor carpi radialis brevis; ECRL: extensor carpi radialis longus; R: radius.

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Distal intersection syndrome is caused by mechanical rubbing between the long abductor and short extensor tendons of the thumb and the tendons of the radial carpal extensors (short and long) that are beneath the 2 former.2 The 4 tendons intersect forming a 30° angle at about 4–5cm from the radiocarpal joint (Image 2). The main cause of inflammation at this level is rubbing due to overuse through work (typing or carpentry) or sport (golf, rowing and racquet sports) due to repeated flexion and extension of the wrist.3,4

Image 2.

(A) Anatomical path of the tendons involved in distal intersection syndrome. (B) Site of pain in distal intersection syndrome and in De Quervain's tendonitis.

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Diagnosis is usually clinical, depending on the site of the pain and crepitus, and ultrasound can be used to confirm findings of tenosinovitis.5,6 Differential diagnosis must be established with De Quervain's tenosynovitis, Wartenberg syndrome (compressive neuropathy of the superficial sensory branch of the radial nerve) and common extensor tendonitis.7 Finkelstein's manoeuvre can be positive, but the determining finding for diagnosis is the painful area being located at around 5cm from the radiocarpal joint (Image 2).

Treatment is based on the local application of cold, rest with anti-inflammatory drugs, and local injections are often very useful for severe or recurring cases. Surgical treatment to release the II extensor compartment might be necessary for cases that are limiting associated with sports activities.

In sum, distal intersection syndrome should be considered in the differential diagnosis of De Quervain's tenosynovitis of atypical presentation, the location of the most medial and proximal pain, and the presence of crepitus are the key to diagnosis.