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The vastus muscles are three of the four muscles that make up the quadriceps femoris muscle of the thigh. The three muscles are the vastus intermedius, the vastus lateralis, and the vastus medialis. The fourth muscle is the rectus femoris muscle, a large fleshy muscle that covers the front and sides of the femur. The vastus lateralis is the largest and most powerful of the three vasti muscles. It is also called the vastus externus. The vastus medialis arises medially along the entire length of the femur and attaches with the other muscles of the quadriceps in the quadriceps tendon.
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What You'll Learn
The three vastus muscles
The vastus muscles are part of the quadriceps femoris muscle group located in the front of the thigh. Quadriceps femoris is a collective term for the four muscles that cover the front and sides of the femur, which include the three vastus muscles and the rectus femoris. The three vastus muscles are vastus lateralis, vastus medialis, and vastus intermedius. These muscles originate from different parts of the femur bone and join together to form a common tendon, the patellar tendon, which attaches to the patella (kneecap). The main function of the vastus muscles is to extend the knee joint, providing stability and strength during movements such as walking, running, jumping, and climbing.
Let's take a closer look at each of the three vastus muscles:
- Vastus Lateralis: The vastus lateralis is the largest and most powerful of the three vastus muscles. It originates from the greater trochanter of the femur, which is the bony protrusion on the lateral (outer) side of the hip joint. The muscle then descends along the lateral side of the thigh, forming a thick, powerful mass before inserting into the patellar tendon. The vastus lateralis is responsible for extending the knee and also plays a role in lateral (side-to-side) stability of the knee joint.
- Vastus Medialis: The vastus medialis is located on the medial (inner) side of the thigh, opposite to the vastus lateralis. It originates from the linea aspera and supracondylar line of the femur bone. The muscle runs downward and slightly inward, forming a teardrop-shaped muscle belly before merging with the other vastus muscles at the patellar tendon. The vastus medialis helps with knee extension and also provides medial stability to the patella, preventing it from tracking too far inward during movement.
- Vastus Intermedius: The vastus intermedius lies deep to the rectus femoris and is therefore the most centrally located of the three vastus muscles. It originates from the front and lateral surfaces of the femur shaft, between the vastus lateralis and vastus medialis origins. The vastus intermedius inserts into the patellar tendon, blending with the other vastus muscles. This muscle also functions to extend the knee and provides additional stability to the patella during dynamic activities.
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Vastus lateralis
The vastus muscles are three of the four muscles that make up the quadriceps femoris muscle of the thigh. The three muscles are the vastus intermedius, the vastus lateralis, and the vastus medialis. The fourth muscle is the rectus femoris muscle, a large fleshy muscle that covers the front and sides of the femur.
The vastus lateralis is the largest and most powerful of the three vasti muscles. It is also called the vastus externus. It is a unipennate muscle and a member of the anterior compartment of the thigh. It arises from several areas of the femur, including the upper part of the intertrochanteric line, the lower and anterior borders of the greater trochanter, and the outer border of the gluteal tuberosity. These form an aponeurosis, a broad flat tendon that covers the upper three-quarters of the muscle. From the inner surface of the aponeurosis, many muscle fibres originate. The vastus lateralis is the largest component of the quadriceps muscle groups and is positioned laterally about the femur. It is bordered laterally by subcutaneous tissue, and medially, it is bordered by the femur and the VI at the level of the greater trochanter.
The vastus lateralis functions as a primary extender of the knee. In conjunction with the vastus medialis, the vastus lateralis stabilizes the knee joint. It is the largest of the quadriceps, which also includes the rectus femoris, vastus intermedius, and vastus medialis. Together, the quadriceps act on the knee and hip to promote movement, strength, and stability. They provide power for and absorb the impact of daily activities such as walking, running, and jumping. The vastus lateralis muscle is innervated by the muscular branches of the femoral nerve (L2, L3, and L4). The lateral circumflex femoral artery primarily supplies the vastus lateralis. The muscle also receives some blood supply from perforating arteries of the deep artery of the thigh, also known as the profunda femoris.
The vastus lateralis may have two insertional heads in approximately 60% of specimens. These two heads are referred to as the vastus lateralis long head (VLL) and the vastus lateralis obliquus (VLO). A layer of fat or fascia achieves this separation from the longitudinal head in most specimens. The vastus lateralis is the recommended site for intramuscular injection in infants less than 7 months old and those unable to walk, with loss of muscular tone.
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Vastus medialis
The vastus muscles are three of the four muscles that make up the quadriceps femoris muscle of the thigh. The three muscles are the vastus intermedius, the vastus lateralis, and the vastus medialis, located in the middle, on the outside, and inside of the thigh, respectively. The fourth muscle is the rectus femoris muscle, a large fleshy muscle that covers the front and sides of the femur.
The vastus medialis is a teardrop-shaped muscle in the front of the thigh that helps extend the knee and stabilise the kneecap. It is one of the four quadriceps muscles that are crucial to mobility and weight-bearing activities. The muscle originates at a ridge at the upper part of the femur (thigh bone) just below where the ball socket fits into the hip joint. From there, the muscle extends down and across the femur and attaches to the inner edge of the kneecap (patella). The vastus medialis arises medially along the entire length of the femur and attaches with the other muscles of the quadriceps in the quadriceps tendon. The vastus medialis muscle originates from a continuous line of attachment on the femur, which begins on the front and middle side (anteromedially) on the intertrochanteric line of the femur. It continues down and back (posteroinferiorly) along the pectineal line and then descends along the inner lip of the linea aspera and onto the medial supracondylar line of the femur. The fibres converge onto the medial part of the quadriceps tendon and the medial border of the patella.
The vastus medialis is vulnerable to injuries such as strains that can develop over the short and long term. Weakness of the vastus medialis is associated with patellar maltracking and patellofemoral pain. Patellofemoral pain syndrome (PFPS) occurs when the cartilage under the kneecap is damaged due to injury or overuse. This causes knee pain that worsens when using stairs or squatting. PFPS is common among athletes but may also occur after knee surgery. Patellar dislocation can also occur, where the VMO is torn when the knee is dislocated and the patella slips out of its normal position. This can happen during a fall or a blunt-force impact on the knee. Symptoms include swelling, pain, deformity, and an inability to fully extend the knee. Knee osteoarthritis, a form of arthritis caused by ageing-related wear and tear, can reduce the range of motion of the knee.
Treating a VMO injury typically involves rest, ice application, compression, and elevation of the leg, along with over-the-counter pain relievers. Physical therapy and surgery may be needed in severe cases. Physical therapy for the vastus medialis focuses on exercises that target the muscles of the hip, thigh, and knee, such as squats, lunges, and step-ups.
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Vastus intermedius
The vastus muscles are three of the four muscles that make up the quadriceps femoris muscle of the thigh. The three muscles are the vastus intermedius, the vastus lateralis, and the vastus medialis, located in the middle, on the outside, and inside of the thigh, respectively. The fourth muscle is the rectus femoris, a large fleshy muscle that covers the front and sides of the femur.
The vastus intermedius arises from the front and lateral surfaces of the body of the femur in its upper two-thirds, sitting under the rectus femoris muscle and from the lower part of the lateral intermuscular septum. Its fibres end in a superficial aponeurosis, which forms the deep part of the quadriceps tendon. The vastus intermedius is deep to the rectus femoris muscle. With the removal of the sartorius muscle, the vastus intermedius becomes more visible. The vastus medialis and vastus intermedius are closely connected, and they influence the extensor apparatus of the knee joint together.
The vastus intermedius is part of the quadriceps and facilitates knee extension. The descending branch of the lateral circumference femoral artery supplies this muscle. The vastus intermedius is difficult to palpate. It cannot be further stretched by hip extension, nor is it accessible to manipulate with massage therapy to stretch the fibres sideways. Due to being the deeper middle-most of the quadriceps muscle group, the intermedius is the most difficult to stretch once maximum knee flexion is attained.
The vastus lateralis is the largest and most powerful of the three vasti muscles. It arises from several areas of the femur and attaches to the outer border of the patella. It ultimately joins with the other muscles that make up the quadriceps in the quadriceps tendon, which travels over the knee to connect to the tibia.
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Vastus muscle injuries
The vastus muscles are three of the four muscles that make up the quadriceps femoris muscle group in the thigh. The three vastus muscles are the vastus intermedius, the vastus lateralis, and the vastus medialis, located in the middle, on the outside, and inside of the thigh, respectively. The fourth muscle is the rectus femoris.
The vastus medialis muscle, also referred to as the vastus medialis oblique (VMO), plays a crucial role in stabilising the knee during weight-bearing exercises. It originates medially along the femur and attaches to the quadriceps tendon. VMO injuries often occur due to activities that place stress on the muscle, such as sudden increases in running or cycling, intense training regimens, repetitive squats or lunges, and high-impact movements without proper conditioning. These injuries can significantly hinder mobility and everyday function, causing pain and difficulty in running, cycling, climbing stairs, and lifting objects.
The vastus lateralis is the largest and most powerful of the three vastus muscles. It arises from several areas of the femur and forms a broad, flat tendon that covers most of the muscle. The vastus lateralis muscle fibres originate from the inner surface of this tendon, with additional fibres arising from the tendon of the gluteus maximus muscle. The vastus lateralis ultimately joins with the other quadriceps muscles in the quadriceps tendon, which travels over the knee to connect to the tibia.
Injuries to the quadriceps muscle group, including the vastus muscles, are common in athletics and can result in pain and lost time from training and competition. Quadriceps injuries can be classified as either acute or chronic. Acute injuries typically arise from a single traumatic event in contact sports such as rugby, soccer, and basketball, while chronic injuries occur over time due to repetitive micro-traumas to the muscle. Strains and contusions are common types of quadriceps injuries, with the rectus femoris being the most frequently involved muscle in quadriceps strains.
Most mild-to-moderate quad injuries can be treated non-surgically. However, a complete quadriceps tendon tear requires surgery to reattach the tendon. Physical therapy, including exercises to strengthen the hip, thigh, and knee, can aid in recovery and reduce the risk of future injuries.
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Frequently asked questions
Vastus muscles are three of the four muscles that make up the quadriceps femoris muscle of the thigh. The three muscles are the vastus intermedius, the vastus lateralis, and the vastus medialis.
The vastus muscles are primarily responsible for extending the leg and assisting in extending the knee joint.
The vastus lateralis is the largest and most powerful of the three vastus muscles. It arises from several areas of the femur and forms a broad, flat tendon that covers the upper part of the muscle.
