Anatomy and Function of the Vastus Lateralis

The vastus lateralis is a muscle located on the lateral, or outside, part of your thigh. The muscle is one of the four quadriceps muscles and is the largest muscle of that group.

The function of the vastus laterails is to work with the other quad muscles to help extend your knee joint. It is also active in maintaining thigh and kneecap position while walking and running.

This article explores the anatomy and actions of the vastus lateralis, as well as common injuries and conditions that affect it.

Function of the Vastus Lateralis

The vastus lateralis muscle works with your other quad muscles to extend, or straighten, your knee. Functional activities like walking, running, climbing stairs, and rising from a seated position are all accomplished with the quads.

The vastus lateralis and the iliotibial (IT) band—which courses down your lateral thigh next to this muscle—help form the lateral wall of your thigh.

The vastus lateralis directly opposes the vastus medialis muscle on the inner portion of your thigh. These two muscles work together to maintain the appropriate position of your patella (kneecap) in the femoral groove of your thigh bone.

Failure of these muscles to function properly may lead to knee pain from patellofemoral stress syndrome (PFSS).

Anatomy of the Vastus Lateralis

The vastus lateralis originates on the upper inter-trochanteric line of your femur, or thigh bone. It also arises from the base of the greater trochanter and the linea aspera, the supracondylar ridge, and the lateral intermuscular septum.

From its origin, the vastus lateralis courses down your lateral thigh and inserts as part of the lateral quadriceps tendon on the tibal tubercle, an elevated portion of the upper shin. The muscle is a large flat structure and has many attachments with a flat aponeurosis (sheath of connective tissue) on your outer thigh.

Nerve innervation to the vastus lateralis is the femoral nerve arising from lumbar (lower back) level two, three, and four. Blood supply to the muscle is via the lateral circumflex femoral artery of the upper thigh.

Conditions That Affect the Vastus Lateralis

There are many different injuries and conditions that may affect your vastus lateralis and quad muscles, especially if you are an athlete or active adult.

These injuries and conditions include:

• Patellofemoral stress syndrome (PFSS): This occurs when your kneecap tracks improperly in the femoral groove of your knee joint. This leads to pain and difficulty with walking and running.
• Vastus lateralis strain: A sudden force to your thigh may cause the quad muscle to be strained. This can cause pain, swelling of the muscle, and bruising of your thigh, and may limit your ability to walk normally.
• Patellar tendinitis: Irritation of the quad tendon that courses over your kneecap may cause patellar tendinitis.
• Weakness due to femoral nerve compression: Your femoral nerve may become pinched or irritated due to lumbar stenosis, arthritis, or a herniated disc. When this occurs pain, numbness, tingling, or weakness in your thigh may result.
• Iliotibial band friction syndrome: Sometimes the IT band becomes irritated due to tight or weak muscles, and the vastus laterals muscle may be implicated in this condition.

Your healthcare provider can diagnose your condition and help guide you in your recovery.

Vastus Lateralis Injury Rehabilitation

Injury to your vastus lateralis or quad muscles may cause pain, swelling of your thigh, or limited walking ability. There are various treatments available that may help you recover after a vastus lateralis injury.

Working with a physical therapist may be helpful when rehabbing vastus lateralis injuries.

Heat and Ice

In the first few days after injury, ice may be applied to your lateral thigh to control pain and decrease swelling and inflammation. Ice should be applied for 10 to 15 minutes, with care taken to avoid frost burns.

Two to three days after injury, you may switch to heat to promote circulation and improve tissue mobility. Heat should be applied for 10 to 15 minutes. Again, care should be taken to avoid burns.

Massage

Massage may be used after a quad or vastus lateralis injury to help decrease pain and promote circulation.

Massage techniques can improve tissue mobility prior to stretching to help improve quadriceps motion.

Stretching

After a vastus lateralis injury, quad stretching may be done to improve mobility and function of the muscle group.

• The prone towel quad stretch: Lie on your stomach and place a towel or strap around your ankle. Bend your knee up, and gently pull on the towel to bend your knee fully. A pulling sensation should be felt in the front of your thigh. Hold the stretch for 30 seconds and release. The stretch can be repeated three times.
• The half-kneeling quad and hip flexor stretch: To do this stretch, kneel down on one knee. Slowly move your body forward until a stretch is felt in the front of your hip and thigh. Hold this position for 30 seconds and then relax back to the starting position. Repeat three times.

Back Exercises

If femoral nerve irritation coming from your low back is causing your thigh pain or weakness, exercises to release the nerve may be helpful. They may include:

• Prone press-ups
• Supine lumbar flexion
• The lumbar side glide exercise

The exercises are designed to get pressure off your lumbar nerve, and postural correction exercises may be done to maintain decompression of the nerve.

Strengthening Exercises

Weakness to your vastus laterals and quads may be causing your injury, and strengthening exercise may be prescribed during your rehab. Exercises may include:

• Straight leg raises
• Leg extension exercises
• Squats
• Lunges
• Hip-strengthening exercises

Strengthening exercises should be done two to four times a week with appropriate rest in between sessions.

Be sure to stop any exercise if it causes pain in your vastus lateralis or quad muscle.

Functional Training

Getting back to normal function after a vastus lateralis injury should be your main goal, and your physical therapist may have you engage in functional training to accomplish that goal.

Balance exercises and sport-specific plyometric training may be done to ensure that your quad is functioning normally.

Be sure to work with your healthcare provider to understand your specific course of rehab. By understanding the anatomy and function of the vastus lateralis, you can be sure to properly rehab the muscle after injury.