Melorheostosis is a rare dysplastic bone formation disease that can also affect the joints. We present a case of a patient with knee pain that was radiographically diagnosed as melorheostosis because of "dripping wax" image. An exploratory arthroscopy was made. In the joint, we found hyperplasic synovial tissue and an increased retropatellar Hoffa pad, which was surrounding an intra-articular ossification resulting from the disease. This was removed and led to a clinical and functional improvement.