Medical device or instrument for diagnosing pressure ulcers using optical reflectance spectroscopy. The device may comprise a tip and a controller. The tip is pressed against the skin of the patient and collects the optical reflectance data. The controller processes the data to determine whether there exists a pressure ulcer and, if there is one, its depth. The tip may also include a pressure sensor for sensing the pressure at which the tip is applied to the patient's skin.