Muscles of the Lower Leg

deep plantarflexors dorsiflexors evertors evertors of the foot extensor digitorum longus extensor hallucis longus extensor retinacula flexor digitorum longus flexor hallucis longus flexor retinaculum muscles of the lower leg peroneal retinacula peroneus brevis peroneus longus peroneus tertius plantarflexors retinacula soleus synovial sheaths tibialis anterior tibialis posterior

Muscles of the lower leg physiotherapy solihull simon evans

Compartments of the Lower Leg

  • Divided into 3 compartments by the intermuscular septa (planes of deep fascia)
    • Anterior compartment - very tight containing the dorsiflexors
    • Posterior compartment - containing the plantarflexors - further divided into deep and superficial
    • Lateral compartment containing the peronei (evertors)

The Retinacula

  • While the majority of the fibres of the deep fascia are orientated longitudinally at the foot and ankle there are a series of ‘bands’ in which the fibres are orientated horizontally
  • These are the retinacula and their role is to stabilise and prevent bowstringing of the tendons 

The Extensor Retinacula

  • Most extensive - 2 parts
  • Superior extensor retinaculum - just above the ankle joint
    • Horizontal fibres from tibia to fibula
  • Inferior Extensor retinaculum - Y shaped, lies over the dorsum of the proximal foot:
    • Stem attaches to the calcaneum in the sinus tarsi
    • Upper arm passes to medial malleolus and 
    • Lower arm goes to blend with the deep fascia on the sole of the foot

The Flexor Retinaculum

  • Situated postero-medially on the ankle
  • Passes from the medial malleolus to the medial aspect, of the calcaneum
  • Septa divide the retinaculum into 4 tunnels
  • Medial to lateral contain:
    • Tibialis posterior tendon
    • Flexor digitorum longus tendon
    • posterior tibial vessels and tibial nerve
    • Flexor hallucis longus tendon

The Peroneal Retinacula

  • 2 Parts
  • Superior Peroneal Retinaculum 
    • pass from lateral calcaneus to the posterior part of the lateral malleolus - Contains the tendons of peroneus longus and brevis in one tunnel
  • Inferior Peroneal Retinaculum
    • lies over the lateral calcaneum directly over the peroneal tubercle - Divided by an intermuscular septum forming 2 tunnels for the tendons of Peroneus Brevis and Peroneus Longus

The Synovial Sheaths

  • As the above tendons pass under the retinacula the are enveloped in a double layer of synovial membrane
  • Role is to prevent friction of the tendons on the bone or against the retinacula
  • Occasionally two tendons may occupy a common sheath (e.g. the two peronei proximally) 

The Plantarflexors

  • Divided into the deep and superficial plantarflexors
  • Superficial plantarflexors include
    • Gastrocnemius - arising form 2 heads
      • Lateral - from lateral aspect of lateral femoral condyle
      • Medial from posterior aspect of medial femoral condyle
      • Inserts into TA - ridge across posterior aspect of calcaneus (with soleus)


    • From the medial tibial border, soleal line, fibrous arch and upper 1/3 of the posterior aspect of shaft of fibula
    • To tendoachilles
    • Together gastrocnemius and soleus are powerful plantarflexors of the ankle - Gastrocnemius will also flex the knee
    • N.S. : Tibial Nerve, Sl, S2
    • Note gastroc & soleus together are sometimes referred to as Triceps Surae 

    Deep Plantarflexors

    • Made up of:
      • Tibialis posterior
      • Flexor digitorum longus
      • Flexor hallucis longus
    • Lie deep to soleus arising as fleshy attachments from the tibia, fibula and interosseus membrane

    Tibialis Posterior

    • From upper lateral ½ of posterior aspect of tibia below soleal line
    • Adjacent I.O. membrane
    • Upper medial ½ of posterior fibula
    • Tendon runs down behind med. mall. in groove (most medial tendon)
    • To medial side of navicular tuberosity and plantar aspect of medial cuneiform
    • (note it sends slips to all the tarsal bones except talus and to the middle 3 M.T bones) 
    • Actions: P.F. and Inversion
    • NS. : tibial nerve L4, 5 

    Flexor Digitorum Longus

    • From the posterior aspect of the middle ½ of shaft of tibia below soleal line
    • Tendon runs down under flexor retinaculum then medial to sust.tali
    • under the medial aspect of the foot it crosses the tendon of F.H.L. and is then joined by flexor accessorius
    • tendon splits into 4 each one going to the bases of the distal phalanx of each of the 4 lateral toes (note it passes through the tendons of F.D.B.) 

    Flexor Hallucis Longus

    • From lower 2/3 of posterior aspect of fibula and adjacent deep fascia
    • Runs down over posterior aspect of ankle joint between talar tubercles
    • Under sustentaculum tali
    • Passes deep to FDL to plantar surface of distal phalanx of big toe (hallux) 
    • N.S. of deep posterior crural Mms is Tibial nerve ( from L4,5, FHL and FDL  L5,Sl,S2) 


    • Tibialis Anterior:
      • From deep surface of covering fascia
      • Upper 2/3 of lateral surface of tibia
      • Adjacent interosseus membrane
      • Runs down over the anterior aspect of the ankle joint under the extensor retinacula...(palpable)
      • To the medial aspect of the underside of the medial cuneiform and base 1st MT 
      • (Joins the tendon of peroneus longus to form a 'stirrup’ for the foot) 

    •  Extensor Digitorum Longus:
      • Superficial and lateral - Mm belly palpable
      • From lateral condyle of tibia (anterior), anterior aspect of head, neck and shaft of fibular (upper 2/3) and adjacent I.O.membrane
      • Runs down and splits into 4 tendons over dorsum of the foot over the heads of the M. T. s it forms an expansion....the Dorsal Digital Expansion
      • with extensions to the dorsal aspect of the bases of all 3 phalanges of the 4 lateral toes

    • Extensor Hallucis Longus:
      • Arises from below EDL....anterior aspect of middle 1/2 of shaft of fibula, adjacent I.O. membrane
      • to dorsal aspect of distal phalanx of hallux

    •  Peroneus Tertius:
      • From lower 1/4 of anterior aspect of shaft of fib
      • to medial aspect of dorsum of base of 5th M.T.
      • P.T. often appears as part of E.D.L.
      • N.S. of the anterior crural muscles:  deep peroneal nerve L4, 5 and S1

    Evertors of the Foot

    • Peroneus Longus:
      • Lies superficial on the lateral aspect of ankle
      • From upper 2/3 of lateral aspect of shaft of fibula....lateral aspect of head.. small slip from lateral condyle of tibia....
      • Tendon runs down behind lat. mall., round peroneal tub., under cuboid in groove
      • to the plantar and lateral surfaces on the medial cuneiform and base of 1st M.T.
    • Peroneus Brevis:
      • Deep to longus
      • From lower 2/3 of lateral aspect of shaft of fibula anterior and inferior to longus
      • runs down initially sharing a common synovial sheath with longus passing behind the lat mall
      • to tubercle on base of 5th M.T
      • NS. of the peronei:  Superficial peroneal nerve L5, Sl  

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