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Plantaris Muscle Anatomy

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Origin
  • Lateral supracondylar line of the femur
Insertion
  • Posterior surface of the calcaneus
Action
  • Assists in plantar flexion of the foot
  • Assists in flexion of the knee
  • Potentially has an important proprioceptive role
Innervation
  • Tibial nerve (S1-S2)
Blood Supply
  • Sural artery
  • Popliteal artery
  • Superior lateral genicular artery
Last updated: Estimated Reading Time: 4 min

Location & Overview

The plantaris muscle is a long, thin muscle that runs down the posterior aspect of the lower leg. It is located superficial to the soleus muscle and deep to the gastrocnemius muscle.[1] Anatomical variations of this muscle can sometimes be present. Examples include complete absence of the muscle (reported in only 7–20% of limbs[2]), termination proximally into the calcaneal tendon, or, in some cases, termination into the gastrocnemius.[3]

The plantaris muscle has an evolutionary relationship with the plantar aponeurosis, a connective tissue structure in the sole of the foot. In several mammals, the plantaris tendon is continuous with the plantar aponeurosis, but in many primates, including humans, this relationship appears to have changed. In humans, the plantaris muscle mainly acts as a weak accessory muscle alongside the gastrocnemius.[4]

plantaris muscle from a posterior view
Pictured here, we can see the plantaris muscle from a posterior view.
plantaris muscle from a posterolateral view
Here we can see the plantaris from a posterolateral view.
Plantaris seen from a medial view
Here we can see the plantaris from a medial view.
plantaris muscle highlighted in red posterior view
Here we can see the plantaris highlighted in red, among the other muscles of the leg, from a posterior view.
plantaris muscle highlighted in red medial view
Here we can see the plantaris highlighted in red, among the other muscles of the leg, from a medial view.

Origin & Insertion

The plantaris muscle originates from the lateral supracondylar line of the femur. The origin is superior and medial to the gastrocnemius’ lateral head. The plantaris continues down the leg, located between the soleus and gastrocnemius, and then along the medial aspect of the calcaneal tendon, next to which it inserts on the calcaneus.[1,5]

origin of the plantaris muscle
Here we can see the origin of the plantaris muscle on the lateral supracondylar line of the femur.
insertion of the plantaris muscle
Here we can see the insertion of the plantaris muscle on the posterior surface of the calcaneus.

Action & Function

The plantaris muscle provides weak plantar flexion at the ankle joint and weak flexion at the knee joint. The gastrocnemius performs these actions more strongly, and the soleus is also a stronger plantar flexor. The soleus does not cross the knee joint, so it cannot assist in knee flexion, unlike the gastrocnemius.[1,6] Some studies have suggested that the plantaris may also play an important proprioceptive role.[7,6,8] Proprioception is the body’s ability to sense movement, action, and position.

Image of a person demonstrating the movement of foot plantar flexion.
This image shows an example of foot plantar flexion, which involves extending the ankle. The opposite of plantar flexion is dorsiflexion. The plantaris muscle can weakly assist with plantar flexion.
Image of a person demonstrating the movement of knee flexion.
In this image, you can see an example of knee flexion, which is the action of bending your knee. The opposite movement of knee flexion is knee extension. The plantaris muscle can weakly assist with knee flexion.

Innervation

The plantaris muscle is innervated by the tibial nerve (S1-S2). The tibial nerve is the larger terminal branch of the sciatic nerve. It also provides innervation for other muscles of the posterior lower leg compartment.[1,9]

Image of the tibial nerve
Highlighted in red, we can see the tibial nerve, which is a branch of the sciatic nerve. The tibial nerve innervates the plantaris muscle from the spinal nerve roots of S1 and S2.

Blood Supply

Blood is supplied to the plantaris muscle via the sural, popliteal, and superior lateral genicular arteries.[5]

Image of the arteries of the lower limb
This image shows the arteries of the lower limb.

References

  1. [1] Spina AA. The plantaris muscle: anatomy, injury, imaging, and treatment. J Can Chiropr Assoc. 2007;51(3):158-65. PMID: 17885678; PMCID: PMC1978447.
  2. [2] Simpson SL, Hertzog MS, Barja RH. The plantaris tendon graft: an ultrasound study. J Hand Surg (Am) 1991;16:708–711.
  3. [3] Egan KG, Emanuelli E, Przylecki W, Endress RD. Variant Plantaris Anatomy During Tendon Harvest. J Hand Surg Am. 2021 May;46(5):431.e1-431.e4. doi: 10.1016/j.jhsa.2021.01.004. Epub 2021 Mar 16. PMID: 33741215.
  4. [4] Sichting, Freddy; Holowka, Nicholas B.; Ebrecht, Florian; Lieberman, Daniel E. (2020-02-26). “Evolutionary anatomy of the plantar aponeurosis in primates, including humans”. Journal of Anatomy. Wiley. 237 (1): 85–104. doi:10.1111/joa.13173. ISSN 0021-8782. PMC 7309290. PMID 32103502
  5. [5] Moore KL, Agur AMR, Dalley AF. Clinically Oriented Anatomy. 8th ed. Philadelphia: Lippincott Williams & Wilkins; 2017.
  6. [6] Moore KL, Dalley AF, editors. Clinically Oriented Anatomy. 5. Philadelphia: Lippincott Williams & Wilkins; 2006. pp. 648–649.
  7. [7] Vlaic J, Josipovic M, Bohacek I, Jelic M. The plantaris muscle: too important to be forgotten. A review of evolution, anatomy, clinical implications and biomechanical properties. J Sports Med Phys Fitness. 2019 May;59(5):839-845. doi: 10.23736/S0022-4707.18.08816-3. PMID: 30936418.
  8. [8] Greene BD, Smith SE, Smith JT. Snapping Plantaris Tendon: A Rare Case in a Competitive Dancer. J Am Acad Orthop Surg Glob Res Rev. 2021;5(5):e21.00008. Published 2021 May 4. doi:10.5435/JAAOSGlobal-D-21-00008
  9. [9] Binstead JT, Munjal A, Varacallo M. Anatomy, Bony Pelvis and Lower Limb, Calf. (Updated 2021 Jun 3). In: StatPearls (Internet). Treasure Island (FL): StatPearls Publishing; 2022 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK459362/

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