The authors produced four cases which all show at first almost the same radiographical espect: an epiphysal defect of the knee. The first case developed in an inflammatory context and proved to be an osteomyelitis. The second case showed a begnin tumour on X-Ray examination a chondroblastoma. Then an epiphysal tuberculosis was produced which at first led to a rather unsettled diagnosis. The last case was a rare observation of chondrome. The diagnostic problems are frequent and besides possible infections localisations, the diagnosis of chondrablastome seems to be the most likely. Surgical approach of such epiphysal lesions is justified not only to corroborate etiology but also in order to avoid an increase in the volume that could impair the epiphysal plate endanger the growth.