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Vastus Intermedius Muscle Anatomy

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Origin
  • Anterior and lateral surface of the femur and lateral intermuscular septum
Insertion
  • Quadriceps tendon, which continues via the patella and patellar tendon to the tibial tuberosity
Action
  • Extends the knee
Innervation
  • Femoral nerve (L2, L3, L4)
Blood Supply
  • Femoral artery
Last updated: Estimated Reading Time: 8 min

Location & Overview

The vastus intermedius muscle is one of the four quadriceps muscles, along with the vastus lateralis, vastus medialis, and rectus femoris. The vastus intermedius is located deep to the rectus femoris, between the vastus medialis and vastus lateralis. It is almost hidden by the other muscles and cannot be palpated.[1] Some studies have also reported a fusion of the vastus intermedius and vastus lateralis muscles.[2,3] In extreme cases of this fusion, the two muscles present as an almost complete fusion.[2]

Pathologies involving the vastus intermedius muscle are less commonly reported compared with other quadriceps muscles, likely due to its deep location. However, strains and contusions can still occur, typically as a result of overuse or direct trauma.[4] Weakness of the vastus intermedius muscle may contribute to instability of the knee joint and increased risk of injury.[4]

Strengthening exercises targeting the vastus intermedius muscle are essential for maintaining knee joint stability and overall lower limb function. Exercises that engage the vastus intermedius include squats, lunges, leg presses, and leg extensions.[4,5] Incorporating these exercises into a well-rounded training program can help prevent injuries and enhance athletic performance.

vastus intermedius anterior view
Here, we can see the vastus intermedius from an anterior view.
vastus intermedius anterolateral view
Here, we can see the vastus intermedius from an anterolateral view.
vastus intermedius lateral view
Here, we can see the vastus intermedius from a lateral view.
vastus intermedius medial view
Here, we can see the vastus intermedius from a medial view.
vastus intermedius highlighted in red among the other muscles of the thigh
Here, we can see the vastus intermedius highlighted in red among the other muscles of the thigh. Because the vastus intermedius is a deep muscle, the other quadriceps muscles have been removed from this image to reveal the vastus intermedius.
Compartments of the thigh
Here, we can see an image of the compartments of the thigh. The vastus intermedius is in the anterior compartment, the section colored green.

Origin & Insertion

The vastus intermedius originates on the anterior and lateral surface of the shaft of the femur.[6] The femur, also known as the thigh bone, is the longest and strongest bone in the human body. The anterior surface refers to the front side of the femur, while the lateral surface refers to the outer side of the bone. The vastus intermedius also originates from the lateral intermuscular septum, a deep fascia fold separating the anterior and posterior compartments of the thigh.[7] The vastus intermedius then inserts into the quadriceps tendon, a strong band of fibrous tissue that connects the muscle to the patella (or kneecap).[8,6] Most of the vastus intermedius’ tendon fibers insert at the base of the patella.[9]

The quadriceps tendon serves as a common insertion point for all four quadriceps muscles, including the vastus intermedius. This shared tendon allows the muscles to work together to extend the knee joint. By connecting to the quadriceps tendon, the vastus intermedius helps with the overall function and stability of the knee joint, alongside the other quadriceps muscles.[1]

The quadriceps tendon connects to the patellar tendon, which in turn inserts onto the tibial tuberosity. The tibial tuberosity is a bony prominence on the upper part of the tibia (shin bone), located just below the knee joint.[1]

Image of the origin of the vastus intermedius
Here, we can see the origin of the vastus intermedius on the anterior and lateral surface of the femur.
Image of the insertion of the patellar tendon and vastus intermedius
Here, we can see the insertion of the patellar tendon. The vastus intermedius fibers insert into the quadriceps tendon, which continues via the patella and patellar tendon to the tibial tuberosity.

Action & Function

The vastus intermedius, along with the other quadriceps muscles (vastus lateralis, vastus medialis, and rectus femoris), plays an important role in extending the knee joint.[9] Knee extension is essential for various daily activities, such as walking, running, climbing stairs, and standing up from a seated position. During these activities, the vastus intermedius contracts and works synergistically with the other quadriceps muscles to straighten the leg at the knee joint.[1]

In addition to knee extension, the vastus intermedius is also involved in maintaining knee stability.[8] As one of the deeper quadriceps muscles, the vastus intermedius provides support to the patella and helps distribute force across the knee joint. This supportive role is useful for maintaining proper knee alignment and preventing excessive stress on the joint during activities that require dynamic knee movements, such as sports and exercise.[10] Moreover, the vastus intermedius contributes to the eccentric control of the knee during activities such as descending stairs and landing from a jump. Eccentric control refers to the ability of a muscle to generate force while lengthening, which acts like a brake to slow down joint movement.[1]

Image of a person demonstrating the movement of knee extension.
In this image, you can see an example of knee extension, which is the action of straightening your leg at the knee. The opposite movement of knee extension is knee flexion. The main action of the vastus intermedius muscle is knee extension.

Innervation

The vastus intermedius muscle receives its innervation from the femoral nerve, which is derived from the lumbar spinal nerve roots L2, L3, and L4.[9] The femoral nerve is a large nerve that originates from the lumbar plexus in the lower back, passes through the pelvis, and descends into the thigh. It is the primary nerve that innervates the quadriceps muscle group, including the vastus intermedius, vastus lateralis, vastus medialis, and rectus femoris muscles.[1]

Proper function of the femoral nerve is vital for the coordinated movements and stability of the knee. Damage or injury to the femoral nerve can result in muscle weakness or even paralysis, affecting the ability to extend the knee and potentially leading to difficulty when walking or maintaining balance.[11]

Femoral nerve highlighted in red
Here, we can see the femoral nerve highlighted in red. The femoral nerve innervates the quadriceps muscle group, including the vastus intermedius. The femoral nerve originates from the spinal nerve roots of L2, L3, and L4.
Image of the quadriceps muscle group innervation by the femoral nerve
Here, we can see the innervation of the quadriceps muscle group; the femoral nerve is a major branch of the lumbar plexus.

Blood Supply

Blood is supplied to the vastus intermedius via the femoral artery. The femoral artery begins at the inguinal ligament as the continuation of the external iliac artery. It courses through the femoral triangle of the thigh, continuing down the leg and supplying the many muscles and structures within this region, including the quadriceps muscles.[12,9]

Image of the arteries of the lower limb
This image shows the arteries of the lower limb, including the femoral artery.

References

  1. [1] Moore KL, Agur AMR, Dalley AF. Clinically Oriented Anatomy. 8th ed. Philadelphia: Lippincott Williams & Wilkins; 2017.
  2. [2] Willan PL, Mahon M, Golland JA. Morphological variations of the human vastus lateralis muscle. J Anat. 1990 Feb;168:235-9. PMID: 2323995; PMCID: PMC1256904.
  3. [3] Becker I, Woodley SJ, Baxter GD. Gross morphology of the vastus lateralis muscle: An anatomical review. Clin Anat. 2009 May;22(4):436-50. doi: 10.1002/ca.20792. PMID: 19306318.
  4. [4] Escamilla RF, Fleisig GS, Zheng N, Barrentine SW, Wilk KE, Andrews JR. Biomechanics of the knee during closed kinetic chain and open kinetic chain exercises. Med Sci Sports Exerc. 1998 Apr;30(4):556-69. doi: 10.1097/00005768-199804000-00014. PMID: 9565938.
  5. [5] Signorile JF, Weber B, Roll B, et al. A comparative electromyographical investigation of the squat and knee extension exercises. J Strength Cond Res. 1994 Aug;8(3):178-83. doi: 10.1519/00124278-199408000-00006.
  6. [6] Yoshida S, Ichimura K, Sakai T. Structural diversity of the vastus intermedius origin revealed by analysis of isolated muscle specimens. Clin Anat. 2017 Jan;30(1):98-105. doi: 10.1002/ca.22791. Epub 2016 Oct 31. PMID: 27598432.
  7. [7] Waligora AC, Johanson NA, Hirsch BE. Clinical anatomy of the quadriceps femoris and extensor apparatus of the knee. Clin Orthop Relat Res. 2009 Dec;467(12):3297-306. doi: 10.1007/s11999-009-1052-y. Epub 2009 Aug 19. PMID: 19690926; PMCID: PMC2772911.
  8. [8] Grob K, Manestar M, Filgueira L, Kuster MS, Gilbey H, Ackland T. The interaction between the vastus medialis and vastus intermedius and its influence on the extensor apparatus of the knee joint. Knee Surg Sports Traumatol Arthrosc. 2018 Mar;26(3):727-738. doi: 10.1007/s00167-016-4396-3. Epub 2017 Jan 25. PMID: 28124107.
  9. [9] Bordoni B, Varacallo M. Anatomy, Bony Pelvis and Lower Limb, Thigh Quadriceps Muscle. 2021 Jul 22. In: StatPearls (Internet). Treasure Island (FL): StatPearls Publishing; 2021 Jan–. PMID: 30020706.
  10. [10] Neumann DA. Kinesiology of the Musculoskeletal System: Foundations for Rehabilitation. 3rd ed. St. Louis, MO: Elsevier; 2017.
  11. [11] Luo TD, Ashraf A, Dahm DL, Stuart MJ, McIntosh AL. Femoral nerve block is associated with persistent strength deficits at 6 months after anterior cruciate ligament reconstruction in pediatric and adolescent patients. Am J Sports Med. 2015 Feb;43(2):331-6. doi: 10.1177/0363546514559823. Epub 2014 Dec 2. PMID: 25466410.
  12. [12] Hammond E, Nassereddin A, Costanza M. Anatomy, Abdomen and Pelvis: External Iliac Arteries. (Updated 2022 Aug 8). In: StatPearls (Internet). Treasure Island (FL): StatPearls Publishing; 2023 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK519552/

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