Resumen Objetivo: El vasto medial ha sido descrito como un musculo conformado por dos unidades. La anatomia y electrofisiologia sugieren una distincion entre fibras proximales y distales. Existe aun controversia en la anatomia y funcion del vasto medial. Metodos y Materiales: En 22 piezas se diseco el cuadriceps e identifico el vasto medial. Se midio el angulo de direccion de las fibras del vasto medial, su relacion con el retinaculo medial. Se identifico la inervacion e hizo registro fotografico y se guardaron los datos en una base de datos. Resultados: Se estudiaron 22 piezas de cadaveres frescos en edad promedio de 34 anos (21-50 anos). La direccion de las fibras musculares en los tercios medio, inferior y a nivel del borde superior de la rotula arrojaron un promedio de 28,9°, 43,6° y 54,8°, respectivamente. El nervio del vasto medial ingresaba en promedio 14 cm proximal al borde superior de la rotula. No se identifico en ninguna pieza diferenciacion dentro del musculo vasto medial que correspondiera al vasto medial oblicuo. No encontramos insercion directa del vasto medial en la rotula, terminando la aponeurosis de este musculo dentro del retinaculo medial. Conclusiones: Los resultados encontrados en la orientacion de las fibras son muy cercanos a los reportados por Lieb y Perry de 45°, 56° y 56°, presentando el mismo aumento de superior a inferior. Respecto a la orientacion de las fibras, penetracion del musculo vasto medial en el retinaculo y la inervacion, nos sugieren que no existen dos musculos estructuralmente diferentes componiendo el vasto medial. Palabras Claves: musculo cuadriceps; vasto medial; nervio femoral; anatomia Abstract Objective: The vasto is described as a muscle conformed by two units. The anatomy and electrophysiology suggest a distinction between fibers proximal and distal. There are even controversy in the anatomy and the role of the vasto medial. Materials and methods: In 22 pieces we dissect the quadriceps and identify the vasto medial. Measured the angle of direction of the fibers of vasto medial and its relationship with the medial retinaculum were made. We identify the innervations and made photographic record and were stored in a data base. Results: 22 pieces of fresh cadavers in age 34 year-old average (21-50 years) were studied. The direction of the muscular fibers in the thirds means, inferior and at level of the upper pole of the patella had an average of 28,9°, 43,6° and 54,8°, respectively. The nerve of the vasto medial entered 14 cm on average proximal to the upper pole. It was not identified any differentiation within the muscle vasto medial that corresponded to the vasto medial oblique. We don't find direct insert of the vasto medial in the patella, ending the aponeurosis of this muscle inside the medial retinaculum. Conclusions: The results found in the orientation of the fibers are very close to those reported by Lieb and Perry of 45°, 56° and 56°, presenting the same increased from top to the bottom. Regarding the orientation of the fibers, penetration of the muscle vast medial in the retinaculum and the innervations, those suggest us that there is not two muscles structurally different composing the vasto medial. Key words: quadriceps muscle, vasto medial, femoral nerve, anatomy