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June 6, 2023

Gastrocnemius and Plantaris

Learn about the gastrocnemius and plantaris muscles, their functions, and how to keep them healthy to prevent injuries. Read on for more insights!

Brent Brookbush

Brent Brookbush

DPT, PT, MS, CPT, HMS, IMT

Human Movement Science & Functional Anatomy of the:

Gastrocnemius (and Plantaris)

by Brent Brookbush MS, PES, CES, CSCS, ACSM H/FS

What's in a name?

Gastrocnemius - Originating from the greek roots: "gastro" referring to stomach, and "kneme" referring to leg, or more specifically "shank" - as in lower leg. This roughly translates into "stomach of the lower leg," likely referring to it's shape.

Plantaris - From the latin root plantar relating or pertaining to the sole of the foot.

Fibularis Muscles (Peroneals) - http://classconnection.s3.amazonaws.com/694/flashcards/597694/jpg/lateral_compartment_leg_muscles1312171716591.jpg

Gastrocnemius Muscles:

  • Origin:
    • Medial Gastrocnemius: Proximal and posterior part of the the medial condyle and adjacent part of the femur, capsule of the knee joint (11).
    • Lateral Gastrocnemius: Lateral condyle and posterior surface of the femur, capsule of the knee joint (11).
  • Insertion: Just medial to the midline of the calcaneus via the achilles tendon (11).
    • This muscle is the most superficial of the posterior compartment muscles of the lower leg; enveloped by the crural fascia and lying on top of the soleus. The proximal attachments of this muscle create the inferior borders of the popliteal fossa along with the plantaris on the lateral side.
    • Supported by a chair or using a wall for support, have your partner stand on their toes. Course your fingers around the superficial elliptical heads of the gastrocnemius. If you run your finger across these muscles you should note an indentation approximately midline dividing the lateral and medial heads. Coursing your fingers to the lateral borders of this muscle you will feel the broader, flatter muscle lying deep to the gastrocnemius - the soleus. If you run your fingers inferiorly you will feel these softer, supple muscle blend into the denser, belt like achilles tendon which becomes almost tubular in shape as it extends into its insertion on the calcaneus. Return to the gastrocnemius and follow each head proximally as it runs into the popliteal fossa behind the knee and wraps inside the dense hamstring tendons (12). You should note that the medial gastrocnemius extends further distally and proximally.
  • Nerve: Tibial nerve descending from the sciatic nerve via the lumbosacral plexus with nerves from roots S1 and S2
  • Action:
    • Plantar flexion and knee flexion
      • Medial Gastrocnemius: Inversion of the ankle and internal rotation of the tibia
      • Lateral Gastrocnemius: Eversion of the ankle and external rotation of the tibia
  • Interesting Note: Despite the gastrocnemius looking as if it is the largest muscle in the posterior lower leg the soleus has nearly twice the cross sectional area. In essence, the soleus is the prime mover of plantar flexion, not the gastrocnemius (3).

Cross Section of Lower Leg- Eanatomy - http://d3j7fudf8o8iuo.cloudfront.net/var/ezwebin_site/storage/images/media/images/e-anatomy/lower-limb-anatomy-illustrations-and-diagrams/human-anatomy-cross-sectional-diagram-leg-muscles-tendon-bone-en/2522735-1-eng-GB/human-anatomy-cross-sectional-diagram-leg-muscles-tendon-bone-en_medical512.jpg

Plantaris:

  • Origin: Distal part of the lateral supercondylar line, adjacent part of the popliteal surface and oblique popliteal ligament of the knee joint.
  • Insertion: Posterior and medial aspect of the calcaneus (11).
  • Intersting Note: This muscle has a short muscle belly, but the longest tendon in the human body (12). Further, roughly 10% of the population does not have a plantaris - this is analogous to the palmaris in the forearm and wrist. It is thought these muscles are vestigial and are well developed in reptiles who use this muscle to aid in propulsion.
    • This small thin muscle of the posterior compartment originates just superior and medial to the lateral gastroc on the floor of the popliteal fossa . Deep to the biceps femoris tendons the muscle runs underneath the tibial nerve (mostly) and polpliteal vein, continues over the popliteus, and becomes tendinous as it passes between the medial gastrocnemius and soleus. This tendon may insert into the distal portion of the achilles tendon or may have a separate insertion on the posteromedial calcaneus.
    • With your partner prone and knee flexed locate the head of the fibula. From the fibular head run your fingers medially and superiority into the popliteal fossa until you are just off the head of the lateral gastrocnemius. You should notice a roughly 2 cm thick band of muscle that runs obliquely into the division between the gastroc heads. Inversion and plantar flexion may help you differentiate between the lateral gastrocnemius and plantaris (12).
  • Nerve: Tibial nerve descending from the sciatic nerve via the lumbosacral plexus with nerves from roots L5, S1, sometimes L4 or S2
  • Action: Plantar flexion and knee flexion, and may assist in inversion and tibial external rotation
    • You could think of the plantaris acting like the lateral gastrocnemius at the knee and the medial gastrocnemis at the ankle
    • Although the plantaris contributes very little to force to movement of the knee or ankle it has been implicated as a proprioceptive organ due to a high density of muscle spindles (13).

http://scientia.wikispaces.com/file/view/l499.jpg/30337869/l499.jpg

Integrated Function:

Note the talus between the tibia and calcaneus and blocked on the lateral side by the patella – http://www.eorthopod.com/online-courses/online-courses/images/ContentImages/ankle/ankle_syndesmosis_injury/ankle_syndesmosis_anat01.jpg

Arthrokinematics:

  • The gastrocnemius and plantaris play a role in arthrokinematics of the knee, tibiotalor and talocalcaneal joints.
    • The knee: The lateral and medial gastroc, as well as, the plantaris would contribute to posterior glide, and/or restrict anterior glide of the tibia on femur. Individually, these muscles may contribute to spin or rotation. The lateral gastroc (and plantaris) will contribute to tibial external rotation via posterior glide of the lateral tibial plateau around a relatively fixed medial plateau. The medial gastroc will contribute to tibial internal rotation via a posterior glide of the medial plateau around a relatively fixed lateral plateau. This relationship may partially explain the common occurrence of lateral gastroc trigger points and restriction in those who exhibit "feet turn out" during squatting, gait, and other functional tasks.
    • The Ankle: Arthrokinematics of the ankle can be complex. The involvement of two joints (tibiotalar and talocalcaneal) and the complex shape of the talus can quickly lead to confusion, but let me give you a new way to view this relationship. First, consider the talus a "victim" bone; that is, motion of the talus is dependent on the motion of the distal fibular head, tibia and calcaneus with no muscular attachment to restrict or counteract motion. In essence, the talus is squeezed and manipulated by motion of these bones relative to one another. Most often this results in the talus moving on the tibia in a direction opposite the motion of the calcaneus. (I call this the juice box effect - you squeeze the bottom and stuff comes out the top) Both heads of the gastrocnemius (and plantaris) plantar flex the ankle, pulling the calcaneus superiorly and posteriorly - this results in the talus translating anteriorly on the tibia and drives the talar head inferiorly. The lateral gastroc will contribute to calcaneal eversion which result in a medial glide of the talus on the tibia. The medial gastrocnemius and plantaris will contribute to calcaneal inversion which will result in lateral glide of the talus on the tibia.

Note the relative posterior glide of the medial epicondyle during external rotation of the tibia - now consider the anterior shear force of the lateral condyle on the lateral tibial plateau - https://encrypted-tbn1.gstatic.com/images?q=tbn:ANd9GcTDKVIXMNZ_0J-1rxxi0Js51wi-Va1gUDSYzi5l3TtQsPF0U4XzTQ

Fascial Integration:

My Fascial Hypothesis: Large fascial sheaths not only play a role in the transmission of mechanical force, but may also play a role in dictating the function of muscular synergies. This is likely caused by reducing or increasing tone of invested musculature via reflex arcs formed between mechanoreceptors embedded in the connective tissue and the attached musculature. In this way my view of fascia differs slightly from noted expert on the subject Tom Myers. I think of these large fascial sheaths (specifically the thoracolumbar fascia, iliotibial band, and abdominal fascial sheath) as natures "mother board." A place for mechanical information to be communicated to the nervous system for more efficient recruitment of the muscular system. Despite having a slightly different philosophy it does not change the fact that fascia plays an important communicative role in the human body and we have Tom Myers to thank for his work.

  • These muscles may be part of intricate system of muscles that tension and reinforce the knee capsule during motion, including the vastus lateralis, vastus medialis obliquus  and tensor fascia latae  via the iliotibial band, semimembranosus , articularis genu , and popliteus .
  • The common insertion into the achilles tendon eludes to an obvious, but important fascial synergy between the largest plantar flexors - the gastrocnemius and soleus. This may be an interesting point to begin research on the effect of increased tension on fascial structures, activation of fascial receptors and synergistic muscle activation.

Notice the Gastrocnemius blending into the thick calcaneal (achilles) tendon. http://www.rvuanatomy.com/uploads/1/3/4/5/13457421/pf7c_animated.gif

Behavior in Postural Dysfunction: The lateral gastrocnemius and plantaris have a propensity toward adaptive shortening and over-activity, while the medial gastrocnemius has a propensity toward underactivity. It should be mentioned that this may happen unilaterally, and lead to a functional leg length discrepancy, or an asymmetrical weight shift during dynamic assessment. We only find altered length and activity in Lower Leg Dysfunction (LLD) , as these muscles play no role in Lumbo Pelvic Hip Complex Dysfunction (LPHCD) or Upper Body Dysfunction (UBD) . For more information on a predictive model of postural dysfunction/impairment of the lower leg click on the link below:

In short, the lateral gastrocnemius should be considered during the mobility or flexibility portion of a program and addressed with release and lengthening techniques. Modifications to common calf stretches are discussed in the videos below to preferentially target lateral fibers. The medial gastrocnemius is commonly under-active along with the tibialis posterior. Specific techniques to address the medial gastroc are not necessary as the tibialis posterior activation exercises below would also increase activity of the medial gastroc. The plantaris is not usually addressed specifically, however, any variation of the standing calf stretch would likely lengthen this structure as well. Release techniques may be implicated, but due to the sensitive structures in the popliteal fossa this is likely best left to the hands of an experienced manual therapist.

Plantaris Muscle in the Popliteal Fossa - Gastrocnemius Removed - http://upload.wikimedia.org/wikipedia/commons/thumb/4/49/Slide1ACCA.JPG/800px-Slide1ACCA.JPG

Clinical Implications:

  • Achilles Tendonitis
  • Plantar Fasciitis
  • Peroneal Tendonitis
  • Pes Planus (Flat feet)
  • Shin Splints
  • MTSS (Medial Tibial Stress Syndrome)
  • Ankle impingement
  • Transverse tarsal and tarsometarsal joint dysfunction
  • Cuboid Subluxation
  • Tennis Leg (Non-specific strain of the posterior leg - plantaris rupture is often implicated)

Signs of Altered Length/Tension and Tone:

  • Overhead Squat:
    • Feet Flatten: Short/Over-active
    • Feet Turn-out: Short/Over-active
    • Knees Bow-in: Short/Over-active
    • Knees Bow-out: Short/Over-active
    • Asymmetrical Weight Shift: Short/Over-active on one side
  • Goniometric Assessment:
  • Dorsi Flexion: < 20° (Active Assisted Range of Motion)
  • Inversion and eversion: Goniometry of ankle inversion and eversion would seem be ideal for testing the length of these muscles, but I find that measuring inversion and eversion with a traditional goniometer to be so unreliable (poor inter- and intra-tester reliability) that it is essentially useless. Further, it is likely that without paired dorsiflexion and inversion the limiting structures of inversion are the lateral ligamentous structures of the ankle.
  • Gastrocnemius Trigger Points
    • Palpation results in tenderness (trigger points or tender points) and may result in radiating symptoms along the posterior leg up through the popliteal fossa. Based on the theoretical model of trigger point development (8) it would seem likely that "trigger points" are dysfunction at the "motor point" of a muscle. You may find the motor point map created by this research study helpful in directing patients/clients to the appropriate location - Motor Point Map

Gastrocnemius Trigger Points - http://www.triggerpoints.net

Bibliography:

  1. Phillip Page, Assessment and Treatment of Muscle Imbalance: The Janda Approach © 2010 Benchmark Physical Therapy, Inc., Clare C. Frank, and Robert Lardner
  2. Dr. Mike Clark & Scott Lucette, “NASM Essentials of Corrective Exercise Training” © 2011 Lippincott Williams & Wilkins
  3. Donald A. Neumann, “Kinesiology of the Musculoskeletal System: Foundations of Rehabilitation – 2nd Edition” © 2012 Mosby, Inc.
  4. Michael A. Clark, Scott C. Lucett, NASM Essentials of Personal Training: 4th Edition, © 2011 Lippincott Williams and Wilkins
  5. Leon Chaitow, Muscle Energy Techniques: Third Edition, © Pearson Professional Limited 2007
  6. Tom Myers, Anatomy Trains: Second Edition. © Elsevier Limited 2009
  7. Shirley A Sahrmann, Diagnoses and Treatment of Movement Impairment Syndromes, © 2002 Mosby Inc.
  8. David G. Simons, Janet Travell, Lois S. Simons, Travell & Simmons’ Myofascial Pain and Dysfunction, The Trigger Point Manual, Volume 1. Upper Half of Body: Second Edition,© 1999 Williams and Wilkens
  9. Cynthia C. Norkin, D. Joyce White, Measurement of Joint Motion: A Guide to Goniometry – Third Edition. © 2003 by F.A. Davis Company
  10. Cynthia C. Norkin, Pamela K. Levangie, Joint Structure and Function: A Comprehensive Analysis: Fifth Edition © 2011 F.A. Davis Company
  11. Florence Peterson Kendall, Elizabeth Kendall McCreary, Patricia Geise Provance, Mary McIntyre Rodgers, William Anthony Romani, Muscles: Testing and Function with Posture and Pain: Fifth Edition © 2005 Lippincott Williams & Wilkins
  12. Andrew Biel, Trail Guide to the Human Body: 4th Edition, © 2010
  13. Moore KL, Dalley AF, editors. Clinically Oriented Anatomy. 5. Philadelphia: Lippincott Williams & Wilkins; 2006. pp. 648–649.

© 2014 Brent Brookbush Questions, comments, and criticisms are welcome and encouraged.

Specific Techniques for Lateral and Medial Gastrocnemius:

Gastrocnemius Self-Administered Release:

Static Calf Stretch with Modifications for Lateral Structure Extensibility:

Slant Board Calf Stretch with Modification for Lateral Structure Extensibility:

Active Calf Stretch with Modifications for Lateral Structure Extensibility:

Dynamic Calf Stretch with Modifications for Lateral Structure Extensibility:

Manual Calf Stretch:

Tibialis Posterior Activation (Medial Gastrocnemius Included):

Tibialis Posterior Activation Progression (Medial Gastrocnemius Included):

Tibialis Posterior Reactive Activation (Medial Gastrocnemius Included):

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