Carbon biomedical devices are widely used in prosthetic surgery; their biocompatibility is excellent and cutaneous or mucosal adverse effects of carbon material remain exceptional. We describe a patient who developed an eczematous dermatitis on the right knee in the vicinity of a ligamentoplasty performed 2 months earlier. Patch testing with the carbon ligament was positive. Although the scattering of carbon material in the surrounding tissues is well known, cutaneous complications have, to our knowledge, never been reported.