A 14-year-old male high school basketball player presented complaining of 2 weeks of right knee pain that began after mild trauma. Imaging revealed a lytic lesion within and crossing the distal femoral epiphysis, below the articular surface of the medial trochlea. Needle biopsy confirmed diagnosis of chondroblastoma. Full-length lower extremity X-ray revealed a leg length discrepancy of 4 mm, right longer than left. He underwent excisional curettage of the lesion with arthroscopic assistance, followed by fat grafting in attempt to prevent physeal bar formation. Surgery proceeded according to the two-portal technique, as described above (Fig. 4). The laterally based physeal tunnel was created distal to the physis, which served as the viewing portal. The working portal was a medially based tunnel, through which instruments were inserted. This two-tunnel technique provided minimal disruption to the physis, while facilitating "real-time" visualization of the excision (Fig. 5). After curettage, fat autograft was inserted into the defect to prevent physeal bar formation. The patient is 12 months from surgery with normal range of motion and function and no evidence of local recurrence.