The present disclosure describes example systems, methods, apparatuses, and medical devices for obtaining physiological parameter data from a wearable patient monitoring device. An example patient monitoring device can include an emitter and a detector. The emitter can emit light through tissue of a patient. The detector can sense the light after it passes through and is attenuated by the tissue and can generate a signal indicative of the sensed light. When the patient monitoring device is attached to or worn by the patient, the emitter and detector are aligned such that the light from the emitter travels through an opening between a first bone and a second bone of the patient prior to being sensed by the detector.