Calcifying tendinitis, or calcific tendinopathy, is a self-limited disorder of unclear etiology, which is characterized by the formation of calcium hydroxyapatite in the tendon, potentially followed by its spontaneous resorption, and then subsequent tendon healing. This condition has been reported to occur most often in the rotator cuff tendons but has also been described to involve tendons at other sites of the body, such as the pectoralis major, gluteus maximus, gluteus medius, adductor magnus, and deltoid insertions. At these other sites, cortical erosion of nearby bone has been noted, potentially mimicking a neoplastic process. This phenomenon of cortical erosion due to concretions has previously been less often described to occur in both the femur and humerus. We present another case of calcifying tendinitis, but involving the infraspinatus tendon with cortical erosion of the greater tuberosity, which we believe is new to the current literature.