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Foot and Ankle Anatomy and Examination

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Ovid: 5-Minute Orthopaedic Consult

Editors: Frassica, Frank J.; Sponseller, Paul D.; Wilckens, John H.
Title: 5-Minute Orthopaedic Consult, 2nd Edition
> Table of Contents > Foot and Ankle Anatomy and Examination

Foot and Ankle Anatomy and Examination
Marc D. Chodos MD
Basics
Description
  • The major function of the foot and ankle
    is to allow even stress distribution between the foot and lower
    extremity during walking and running.
  • For adequate function, the foot must be plantigrade (i.e., rest evenly flat on the ground) and painless.
  • The muscles that control foot and ankle
    function include extrinsic (originating outside the foot) and intrinsic
    (originating within the foot) groups.
  • Extrinsic muscles: 4 groups of muscles and tendons (dorsiflexors, evertors, plantarflexors, and invertors):
    • Dorsiflexors:
      • Extensor tendons: Tibialis anterior, extensor digitorum longus, and extensor hallucis longus
      • Easily palpable crossing the ankle; can be lacerated by sharp objects
    • Evertors:
      • Peroneus longus and brevis
      • Situated on the lateral aspect of the leg
      • Tendons run posterior to the lateral malleolus.
      • Injury to tendon sheath can cause tendon subluxation over malleolus.
    • Plantarflexors and invertors:
      • Travel posteromedial to the ankle
      • The PTT, the main invertor, is prone to tenosynovitis and rupture in the adult, a condition leading to acquired flatfoot.
      • The extrinsic toe flexors include the flexor digitorum longus and flexor hallucis longus.
  • Intrinsic foot muscles include 1 dorsal layer and three plantar layers, all of which help to control toe motion.
  • An imbalance between extrinsic and
    intrinsic muscle strength can contribute to toe deformities such as
    mallet toes, claw toes, and hammer toes.
  • Foot and ankle bones are easily palpable.
    • The ankle joint:
      • Consists of the articulation between the distal tibia, fibula, and talus
      • Predominantly allows plantar- (40°) and dorsiflexion (20°)
      • Is supported by several ligaments:
        • Anterior and posterior tibiofibular ligaments stabilize the syndesmosis; if injured, “high ankle sprain” results.
        • The superficial and deep deltoid ligaments connect the medial malleolus to the hindfoot.
        • The ATFL, CFL, and PTFL support the lateral ankle; the ATFL commonly is injured in inversion ankle sprains.
    • The hindfoot:
      • Consists of the talus and calcaneus, which articulate at the subtalar joint
      • Allows inversion and eversion (40° arc of motion), which is important when walking on uneven surfaces.
      • The talus is covered almost completely
        with cartilage; its blood supply frequently is disrupted during
        subtalar dislocation or talar fracture, leading to AVN.
      • The calcaneus acts as a shock absorber; axial loading from a fall is a common mechanism of calcaneal fracture.
    • The midfoot:
      • Consists of 2 rows of bones:
        • Proximally, the navicular and the cuboid articulate with the hindfoot through the Chopart joint.
        • Distally, the 3 cuneiform bones and cuboid articulate with the metatarsals via the tarsometatarsal (Lisfranc) joint.
      • Ligaments attach all but the 1st and 2nd metatarsal bases to the adjacent metatarsals.
      • The strong Lisfranc ligament connects the 2nd metatarsal to the medial cuneiform.
    • The forefoot consists of the 5 metatarsals and 14 phalanges (2 phalanges in the hallux and 3 in each of the lesser toes).
  • The gait cycle consists of the stance and swing phases.
    • Stance phase: Heel strike, foot flat, toe-off:
      • Heel strike:
        • Tibialis anterior and long toe extensors are active.
        • The foot is pronated, which unlocks the
          Chopart joint, makes the midfoot flexible, and helps with energy
          absorption and load acceptance.
      • Foot flat:
        • Tibialis posterior and peroneals are active.
        • The leg rotates externally, which supinates and locks the midfoot and stabilizes the foot for weightbearing.
      • Toe-off:
        • Gastrocnemius–soleus complex is active.
        • Dorsiflexion of the toes tightens the
          plantar fascia (windlass mechanism), increasing the midfoot arch and
          locking the midfoot, which allows the foot to act as a lever during
          push-off.
    • Swing phase: Tibialis anterior and long toe extensors are active.
Diagnosis
Signs and Symptoms
History
  • Address the patient’s symptoms:
    • Mechanism of injury for acute trauma
    • Pain: Severity, location, quality, radiation, and alleviating/aggravating factors
    • Mechanical symptoms (locking/catching) and instability
    • Neurologic symptoms: Numbness, dysesthesia, paresthesias
  • Pertinent medical and surgical history:
    • Diabetes, neurologic disorders, vascular disease, inflammatory arthritides
    • Previous foot or leg surgery
  • Shoe wear
  • Occupation
  • Sport or recreational activities
Physical Exam
  • Physical examination findings of the involved extremity should be compared with those of the contralateral extremity.
  • Patient in standing position:
    • Evaluate the patient’s gait pattern and stance to assess ankle/foot alignment.
      • Viewed from behind, alignment of the hindfoot can be determined as varus, neutral, or valgus.
      • More lateral toes seen on the affected
        side than on the uninvolved foot is called the “too-many-toes” sign,
        and implies the presence of flatfoot with arch collapse and midfoot
        abduction.
      • Assess gait pattern for steppage (dropfoot), circumduction, scissoring, or antalgia.
    • Double- and single-limb heel rises allow
      for evaluation of dynamic foot function, including tibialis posterior
      strength, arch reconstitution, and balance.
  • Patient in seated position:
    • Vascular assessment:
      • Palpate the dorsalis pedis on the dorsum
        of the foot lateral to extensor hallucis longus, and the posterior
        tibial pulse behind the medial malleolus.
      • Examine for venous stasis, pitting edema.
    • Sensory and neurologic examination:
      • Dorsal foot (superficial peroneal nerve)
      • 1st dorsal web space (deep peroneal nerve)
      • Medial border of foot (saphenous nerve)
      • Lateral border of foot (sural nerve)
      • Plantar foot (tibial nerve)
      • Patient’s ability to feel the 5.07
        Semmes- Weinstein monofilament on the plantar foot correlates with
        having protective sensation (1).
      • Check reflexes and evaluate for Babinski sign and clonus.
    • Motor examination: Test strength and palpate tendons.
      • Ankle dorsiflexion (tibialis anterior)
      • Ankle plantarflexion (gastrocnemius–soleus complex)
      • Eversion (peroneals)
      • Inversion in plantarflexion (tibialis posterior)
      • Flexion and extension of the distal
        phalanx of the great toe (flexor and extensor hallucis longus);
        evaluate active and passive motion.
      • Ankle plantar and dorsiflexion, with any hindfoot deformity passively corrected

        • P.143


      • Hindfoot inversion and eversion to assess subtalar motion
      • Chopart joint abduction/adduction while stabilizing the hindfoot
      • Assess Lisfranc joint with palpation and plantar- and dorsiflexion of the tarsometatarsal joints.
      • Assess motion at the MTP and toe joints.
    • Palpation:
      • Medial and lateral malleoli (fracture)
      • Ankle joint for tenderness, effusion (osteochondral lesion, synovitis)
      • PTT along its course posterior to the medial malleolus to insertion on navicular (tendinitis)
      • Navicular tuberosity ~2 cm distal and
        plantar to medial malleolus (accessory navicular, stress fracture,
        talonavicular pathology)
      • Achilles tendon and retrocalcaneal bursa
        along the posterior ankle and hindfoot for defects, nodules,
        thickening, swelling, and tenderness (tendinitis, tear)
      • Peroneal tendons posterior to the lateral
        malleolus to the brevis insertion on the base of the 5th metatarsal,
        and where the longus passes through the plantar groove of the cuboid
        (tendinitis, 5th metatarsal base fracture); also assess for tendon
        subluxation with foot circumduction.
      • Sinus tarsi ~1 cm distal to lateral malleolus (subtalar joint pathology)
      • Tenderness along the tip of medial or lateral malleolus (ligament sprain)
      • Tenderness between the tibia and fibula proximal to the ankle joint (syndesmosis injury)
      • Palpate the plantar fascia, originating
        at the base of the heel (plantar fasciitis, especially if tenderness is
        accentuated with toe dorsiflexion).
      • Base of the 2nd metatarsal (Lisfranc injury)
      • Plantar MTP joint of the great toe (sesamoiditis, sesamoid fracture)
      • Plantar lesser toe MTP joints (metatarsalgia)
      • Metatarsal interspaces (neuroma)
  • Specific tests and examinations:
    • Anterior drawer test (ankle instability):
      • Try to sublux the talus anteriorly from tibia.
      • Foot dorsiflexed stresses the ATFL.
    • Thompson test:
      • With the patient in the prone position, squeeze the posterior calf.
      • Loss of foot plantarflexion implies disruption of the Achilles tendon (2).
    • Coleman block test:
      • Helps determine if varus hindfoot deformity is flexible or rigid
      • The patient stands on a block with the 1st ray unsupported; if the hindfoot deformity corrects, then it is flexible (3).
    • Lesser toe deformities:
      • Assess the location of the calluses.
      • Assess if the deformity is correctable or not (flexible versus rigid).
      • Assess MTP joint stability with modified drawer test, trying to sublux and reduce proximal phalanx on metatarsal head.
    • Hallux valgus:
      • Assess the location of the calluses.
      • Assess tenderness over the medial eminence.
      • Assess MTP motion with the deformity corrected.
      • Assess for hypermobility of the 1st
        tarsometatarsal joint by stabilizing the lateral foot and attempting to
        translate the 1st metatarsal plantar and dorsal.
      • Assess for lesser toe deformities that could contribute to symptoms.
Tests
Lab
  • If concern for infection exists, consider obtaining ESR, C-reactive protein, and white blood cell count.
  • Joint aspirations should be sent for cell count, differential, Gram stain, evaluation for crystals, and culture.
Imaging
  • Plain radiographs:
    • If the patient has acute trauma, and fracture or dislocation is being considered, obtain nonweightbearing films.
    • If the patient is able to stand, then weightbearing radiographs should be obtained.
      • Standing radiographs show bony
        relationships in the physiologic state and are much more likely to
        reveal foot disorders than are nonweightbearing views.
    • Stress view radiographs help to evaluate indirectly the integrity of ligamentous structures.
  • CT is helpful for identifying and delineating fracture patterns and bony pathology, especially of the midfoot and hindfoot.
  • MRI helps to show soft-tissue disorders,
    including tendon and ligament pathology, soft-tissue lesions, subtle
    fractures, and infection.
  • Technetium-99m bone scans:
    • Useful for localizing problems when the complaint is vague or multifocal
    • Can help locate stress fractures, tumors, and other pathology
  • Indium-labeled white blood cell scans:
    • Useful for identifying infection
    • Combined with a marrow scan, can help differentiate infection and Charcot arthropathy
References
1. Olmos
PR, Cataland S, O’Dorisio TM, et al. The Semmes-Weinstein monofilament
AS a potential predictor of foot ulceration in patients with
noninsulin-dependent diabetes. Am J Med Scin 1995;309:76–82.
2. Thompson TC. A test for rupture of the tendo Achilles. Acta Orthop Scand 1962;32:461–465.
3. Coleman SS, Chesnut WJ. A simple test for hindfoot flexibility in the cavovarus foot. Clin Orthop Relat Res 1977;123:60–62.
Additional Reading
Mann RA. Principles of examination of the foot and ankle. In: Mann RA, Coughlin MJ, eds. Surgery of the Foot and Ankle, 6th ed. St. Louis: Mosby-Year Book Inc., 1993:45–60.
Michelson J. Foot and ankle biomechanics. In: Mizel MS, Miller RA, Scioli MW, eds. Orthopaedic Knowledge Update: Foot and Ankle 2. Rosemont, IL: American Academy of Orthopaedic Surgeons, 1998:1–9.
Resch S. Functional anatomy and topography of the foot and ankle. In: Myerson MS, ed. Foot and Ankle Disorders. Philadelphia: WB Saunders, 2000:25–49.
Shuler FD. Anatomy. In: Miller MD, ed. Review of Orthopaedics, 4th ed. Philadelphia: WB Saunders, 2004:660–668.
Miscellaneous
FAQ
Q: What anatomic structure causes a Tillaux fracture?
A:
In adolescents, fusion of the distal tibial physis begins centrally and
progresses medially. The lateral portion of the physis is the last area
to fuse. The ATFL attaches to this part of
the tibia. A twisting injury to the ankle at this stage of development
can cause this ligament to avulse the unfused segment of tibial physis,
with extension of the fracture into the ankle joint.
Q: What is the main blood supply to the talar body?
A:
The artery of the tarsal canal, a branch of the tibial artery, is the
main blood supply to the talar body. Branches of the dorsalis pedis and
peroneal artery also provide limited blood supply to the talus. Injury
to this vascular network can cause AVN of the talar body.

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