Muscle Group: Vastus Lateralis is the largest of the quadriceps muscles
Location: Outer part of the front of the thigh
Action: Knee extension (straightening)
Origin: Several areas of the femur – upper lateral part intertrochanteric line, lower border greater trochanter, lateral side gluteal tuberosity, upper half lateral lip of linea aspera, lateral intermuscular septum
Insertion: Rectus femoris tendon and lateral border of the patella
Functional Activities: Sit to stand, stairs and squats
Nerve Supply: Muscular branch femoral nerve (L2, L3, L4)
Vastus Lateralis (also known as Vastus Externus) is the largest and most powerful of the quadriceps muscles, found on the lateral (outer) side of the front of the thigh. It originates from various parts of the femur (thigh bone) over a large area as listed above. These parts blend together to form a broad, flat tendon (known as an aponeurosis) from which come the muscle fibres that run downwards and forwards to the knee joint.
The main muscle bulk of vastus lateralis is found on the upper half of the lateral side of the thigh. It then forms a broad tendon which narrows as it approaches the patella (kneecap).
Here, the tendon inserts into one of the other quadriceps tendons (rectus femoris) and the outer side of the patella. Some fibres blend with the iliotibial band (ITB) which to a large extent replaces the local part of the joint capsule and then attaches to the tibial tuberosity, just below the patella.
It works with the other quadriceps muscles to extend the knee, particularly with activities such as getting up from a chair, climbing stairs and cycling. Vastus Lateralis is the recommended site for intramuscular injections in infants under seven months old and in those with loss of muscle tone, usually due to not being able to walk.
Tightness in vastus lateralis and resultant lateral retinaculum tightness can cause the patella to shift or tilt which can cause problems with patella tracking and increase the risk of patellar dislocation. This tightness can be treated with stretching exercises or lateral release knee surgery.
Here are some other topics you may be interested in:
1) Knee Strengthening Exercises: Loads of great ways to strengthen the quadriceps and other knee muscles. Easy to follow video guides
2) Quads Stretches: Simple test to see if your quads are tight and some great knee stretching exercises you can do at home
3) Knee Muscles: Find out about the other muscles around the knee, how they fit together and how they work
4) Common Knee Problems: Find out all about the most common things that go wrong in the knee and how to fix them