Dysplasia epiphysealis hemimelica, also known as Trevor Fairbank disease, is characterized by asymmetrical osteochondral overgrowth of the epiphyseal cartilage. The clinical presentation of dysplasia epiphysealis hemimelica is wide and variable, depending on the site of the lesion. Herein, we describe the physical examination of a 9-year-old boy with intra-articular dysplasia epiphysealis hemimelica, in whom the symptoms were elicited on "reverse Wilson's sign": bending the knee from 70° to 120° against resistance while externally rotating the tibia. Arthroscopic treatment of the intra-articular dysplasia epiphysealis hemimelica of the knee showed good outcome; hence, this modality should be considered for the management of intra-articular dysplasia epiphysealis hemimelica.