Summary Intersection syndrome is an inflammatory condition that occurs at the crossing point of the 1st dorsal compartment (APL and EPB ) and the 2nd dorsal compartment (ECRL, ECRB). Diagnosis is made clinically with pain over the dorsoradial forearm (5 cm from wrist joint) made worse with resisted wrist extension and thumb extension. Treatment is conservative with rest, wrist splinting and steroid injections. Epidemiology Incidence rare < 1 per 100,000 annually Demographics males = females Risk factors rowing skiing horseback riding weight lifting Etiology Pathophysiology mechanism is repetitive wrist extension repetitive motion results in friction at the crossover junction of the 1st and 2nd dorsal compartments friction leads to and inflammatory response and subsequent tenosynovitis Anatomy Extensor tendon compartments Compartment 1 (De Quervain's Tenosynovitis ) APL EPB Compartment 2 (Intersection syndrome) ECRL ECRB Compartment 3 EPL Compartment 4 EIP EDC Compartment 5 (Vaughan-Jackson Syndrome ) EDM Compartment 6 (Snapping ECU ) ECU Presentation Symptoms pain over dorsal forearm and wrist Physical exam tenderness on dorsoradial forearm approximately 5cm proximal to the wrist joint provocative tests crepitus over area with resisted wrist extension and thumb extension Imaging Radiographs not required for the diagnosis or treatment of intersection syndrome MRI indications to confirm diagnosis when clinical findings unclear views fluid sensitive sequences (short tau inversion recovery, STIR; fat suppressed proton density, FS PD; T2-weighted) findings most characteristic is peritendinous edema or fluid surrounding the 1st and 2nd extensor compartments other findings - tendinosis, muscle edema, tendon thickening, loss of the normal comma shape of the tendon, and juxtacortical edema may also be seen Differential De Quervain's tenosynovitis Wartenberg's syndrome Diagnosis Clinical diagnosis is made with careful history and physical examination Treatment Nonoperative rest, wrist splinting, steroid injections indications first line of treatment technique injection aimed into 2nd dorsal compartment (ECRL, ECRB) Operative surgical debridement and release indications rarely indicated in recalcitrant cases technique release of the 2nd dorsal compartment approximately 6 cm proximal to radial styloid