We report 5 cases of a localized lesion (4 with osteomyelitis and 1 with an intraosseous ganglion cyst) that were treated successfully by medulloscopy. Medulloscopy is a standard arthroscopic technique for visualizing the intramedullary canal of the tibia. Two portals were created to allow easy access and triangulation to the lesion, one for the 5-mm arthroscope and the other for the instrument. Debridement, irrigation, and resection of the sequestrum were performed for the cases with osteomyelitis, and the intraosseous ganglion cyst was treated with biopsy, debridement, and autogenous bone grafting. All cases were treated successfully with medulloscopy and did not show recurrence at the last follow-up. In addition, there were no complications related to the procedure.