We describe a patient with spondyloepiphyseal dysplasia and precocious hip osteoarthritis. Bilateral hip arthroplasty was performed at the age of 14 1/2 years. Pathologic examination revealed severe osteoarthritic deformities: flattened and deformed femoral heads, were almost completely covered by abnormal cartilaginous, fibrocartilaginous and fibrous tissues showing intense degenerative and regenerative processes. The electron microscopic examination of chondrocytes showed large intracytoplasmic accumulations of glycogen and of microfilaments and many small vesicles suggesting intense micropinocytosis and/or microexocytosis.