The fifth head of quadriceps femoris: for sure?

PURPOSE The quadriceps femoris has been described as a muscle composed by four heads: rectus femoris, vastus lateralis, vastus medialis and vastus intermedius. Each head fuse with the other ones making up the quadriceps tendon, which inserts into the patella. Nevertheless, there has been described a fifth component of the quadriceps muscle in recent anatomical publications. Understanding this fifth head may be important for orthopedics and radiologist. METHODS Cadaveric dissection of left thigh of a female 83 years old was performed to demonstrate a fifth head of the quadriceps femoris muscle. RESULTS In this study, a fifth head of the quadriceps femoris muscle was found in the left thigh of a female cadaver 83 years old. This fifth head was made up by four independent muscular fascicles attaching in a common flat tendon that joins distally with the lateral border of the quadriceps tendon. The fifth head found was supplied by branches of the ascending branch of the lateral femoral circumflex artery and by branches of the deep lateral division of the femoral nerve. CONCLUSIONS The incidence of this fifth belly in cadaveric studies has been reported as a range from 29 to 100%. However, no published articles refer an anatomical finding such as this multi-bellied fifth head. The knowledge of the existence and location of the fifth belly is necessary to make accurate diagnosis of QF muscle strains. Its anatomical course may be involved in patellar tracking.