The vastus lateralis is the largest muscle in the quadriceps group. It is located on the outer portion of the thigh and is important in any movement that requires knee extension. The muscle also helps stabilize the patellar. Although the muscle is the strongest and biggest in the quadriceps femoris muscle group, it works in conjunction with the other three in order to provide stable leg extension at the knee joint.
The quadriceps are made up of four main muscles that assist in a range of actions of the leg. These are known as the vastus lateralis, medialis, intermedius and rectus femoris. The vastus lateralis is the largest muscle in this group and hence has a major role to play in stabilization of the knee.
The origin of the vastus lateralis is on the femur near the hip. It then runs down the lateral side of the thigh and attaches to the knee via the quadriceps tendon. This is also where the other two vastus muscles insert although the rectus femoris inserts at the patella tendon. The innervation of the muscle is via the femoral nerve.
Any movement that requires extension of the knee will invoke the vastus lateralis muscle. For example, walking up or down stairs will require the muscle in order to avoid excessive mobility in the knee joint. Exercises such as cycling also require the vastus lateralis to be strong.
Due to the importance of the vastus lateralis in sporting activities, a number of exercises have been developed to improve the muscle’s strength. For example, squats are a good exercise for working all the quadriceps muscles. Leg press machines can also achieve similar results. Quadriceps strains are relatively common and are categorized as grade one, two or three depending on the severity.
Problems can arise when the vastus lateralis is too strong compared to the vastus medialis, which is located on the inner side of the thigh. These two muscles are thought to work together in order to allow the patellar to track in the patella-femoral groove. Many cyclists, runners and other athletes have weak vastus medialis muscles, which causes lateral tracking of the patellar and can result in a number of knee problems. There is still some debate, however, about the significance of the strength of these two quadriceps muscles or whether knee problems are more likely to arise from issues in the hip and ankle.