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C h e c k o u t A B M P 's l a t e s t n e w s a n d b l o g p o s t s . Av a i l a b l e a t w w w. a b m p . c o m . 47 FUNCTIONAL ANATOMY education Vastus Lateralis By Christy Cael Vastus lateralis is one of four quadriceps muscles located on the front of the thigh. Its fibers lie deep to the iliotibial band and wrap around the outside of the thigh. The thick, oblique fibers of the vastus lateralis originate on the lateral linea aspera, a vertical ridge on the posterior femur, then join the rest of the quadriceps muscles anteriorly and distally at the patellar tendon. As the name implies, it is the most lateral of the four quadriceps muscles, as well as the largest. Vastus lateralis, vastus intermedius, and vastus medialis have the single function of extending the knee. These muscles work in conjunction with the gluteus maximus, hamstrings, and gastrocnemius during squatting motions. The rectus femoris, the fourth quadriceps muscle, is also recruited for this action, but more so when hip flexion is combined with knee extension, such as when swinging the leg forward during gait. Jumping, lifting, standing, and powerful kicking motions all require strong, well-balanced quadriceps muscles. Unfortunately, the vastus lateralis is often overdeveloped compared to the vastus medialis. This imbalance can lead to improper tracking of the patella as the knee flexes and extends. Specifically, the patella can be pulled laterally in the femoral groove, causing pain and wear in the articular cartilage. If severe imbalance is present, the patella can be pulled out of the groove entirely, causing patellar dislocation. This is more common in individuals who have a high quadriceps (or Q) angle. This angle measures bend in the patellar tendon and is determined by the way the femur sits atop the tibia and the location of the tibial tuberosity. Normal Q angle is 5–15 degrees and tends to be higher in females compared to males, due to a wider pelvis. VASTUS LATERALIS Attachments • Origin: Greater trochanter; gluteal tuberosity; and proximal, lateral lip of the linea aspera • Insertion: Tibial tuberosity via the patellar tendon Actions • Extends the knee Innervation • Femoral nerve • L2–4 Vastus lateralis