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)
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 (tib.post. from L4,5, FHL and FDLL5,Sl,S2)
Dorsiflexors
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, adjacentI.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
