Medial compartment disease (MCD) is a recently recognized elbow disorder in dogs and refers to extensivecartilage erosions of the medial compartment of the elbow joint. This report describes a case of MCD in a 10-month-old Large Munsterlander that was presented with right frontleg lameness. Based on signalement,history and radiographic examination, there was a strong suspicion of a fragmented coronoid process (FCP)of the right elbow. However, arthroscopic examination revealed extensive cartilage erosions of the medial partof the humeral condyle and the medial coronoid process in addition to a small coronoid fragment (FCP) anda small OCD-like lesion. After the arthroscopic treatment, the dog did not improve. Neither did additionaltreatment with autologous conditioned plasma (Arthrex ACP®) lead to a substantial improvement. Finally, thedog was euthanized because of persistent lameness.