Local steroid injections are often administered in the office setting for treatment of trigger finger, carpal tunnel syndrome, de Quervain's tenosynovitis, and basal joint arthritis. If attention is paid to sterile technique, infectious complications are rare. We present a case of suppurative extensor tenosynovitis arising after local steroid injection for vague symptoms of dorsal hand and wrist pain. The progression of signs and symptoms following injection suggests a natural history involving bacterial superinfection leading to tendon rupture. We discuss the pitfalls of local steroid injection and the appropriate management of infectious extensor tenosynovitis arising in such situations.