MCQs – Foot/Ankle 1

Modern Study Review (AI-Generated)

High-Yield Summary

Foot and ankle anatomy, including nerve innervation, muscle compartments, ligamentous support, and portal risks, is a staple of the Royal College exam, focusing heavily on surgical approaches and compartment syndrome management. The single most important clinical trade-off is balancing adequate decompression of all nine foot compartments against the risk of injuring the medial and lateral plantar nerves during surgery. While classic exam answers emphasize standard portal placements and anatomical landmarks, modern practice increasingly incorporates ultrasound guidance and minimally invasive techniques to reduce iatrogenic nerve injury. Understanding the spatial relationships of muscles and nerves is critical for safe arthroscopy and compartment syndrome decompression.

High-Yield Decision Matrix

Active Recall Q&A

Nerve Anatomy & Injury

Q: Which nerve innervates the extensor digitorum brevis?
A: The deep peroneal nerve.
Related Pearl: The deep peroneal nerve also provides sensation to the first web space, a key landmark for localizing nerve injuries.

Q: What sensation remains after a complete peroneal nerve injury at the fibular head?
A: Sensation is preserved only along the plantar aspect of the foot (tibial nerve) and the medial aspect of the foot (saphenous nerve).
Related Pearl: The saphenous nerve is a femoral nerve branch that does not cross the knee, explaining preserved medial foot sensation despite peroneal nerve injury.

Muscle Compartments & Anatomy

Q: In the anterior compartment of the leg, where are the EHL, tibialis anterior, and EDL located in cross-section?
A: EHL is most posterior along the interosseous membrane; tibialis anterior lies medially against the tibia; EDL lies laterally.
Related Pearl: This spatial arrangement guides safe surgical approaches and compartment syndrome decompression.

Q: In the lateral compartment, which muscle lies deep: peroneus brevis or peroneus longus?
A: Peroneus brevis lies deep to peroneus longus.
Related Pearl: This layering is critical during lateral ankle surgeries to avoid tendon injury.

Q: Describe the muscle arrangement in the deep posterior compartment.
A: Tibialis posterior lies along the interosseous membrane; flexor digitorum longus is posteromedial; flexor hallucis longus is most lateral.
Related Pearl: The lateral position of FHL explains its surgical approach via the Harmon interval between peroneus brevis and FHL.

Q: Where does the tibialis posterior tendon insert?
A: Into the tarsal navicular.
Related Pearl: Tibialis posterior dysfunction leads to adult acquired flatfoot due to loss of navicular support.

Ligaments & Portal Risks

Q: What is the spring ligament and its function?
A: The plantar calcaneonavicular ligament, elastic and supporting the talar head between calcaneus and navicular.
Related Pearl: Its elasticity maintains the medial longitudinal arch; rupture contributes to flatfoot deformity.

Q: Which structures are at risk with the anteromedial ankle arthroscopy portal?
A: The great saphenous nerve and saphenous vein.
Related Pearl: Injury causes medial ankle numbness and neuropathic pain.

Q: Which structure is at risk with the anterolateral portal?
A: The superficial peroneal nerve.
Related Pearl: The nerve’s variable distal course increases vulnerability during portal placement.

Q: Where do the tibialis anterior nerve and artery run relative to the EHL at the ankle?
A: They run just lateral to EHL, between EHL and EDC tendons.
Related Pearl: Proximally, they are medial to EHL; this positional change is critical for safe portal placement.

Q: How is the anterocentral portal safely created?
A: By going through the extensor digitorum communis tendons to avoid the artery, which lies medial.
Related Pearl: This technique minimizes vascular injury during ankle arthroscopy.

Nerve Pathways & Foot Layers

Q: Where do the medial and lateral plantar nerves pass in the foot?
A: Deep to the abductor hallucis and flexor digitorum brevis muscles.
Related Pearl: Their deep location protects them from superficial injury but complicates surgical exposure.

Q: What composes the superficial layer of the foot?
A: The plantar aponeurosis with the lateral cord attaching to the base of the 5th metatarsal.
Related Pearl: The plantar aponeurosis is involved in plantar fasciitis and avulsions at the 5th metatarsal base.

Q: Which muscles are in the first layer of the foot?
A: Abductor hallucis, flexor digitorum brevis, and abductor digiti minimi.
Related Pearl: These muscles provide primary support for the medial and lateral longitudinal arches.

Q: Which muscles and tendons are in the second layer of the foot?
A: Quadratus plantae, flexor digitorum longus tendons, flexor hallucis longus tendon, and lumbricals.
Related Pearl: Quadratus plantae redirects FDL pull, important in toe flexion mechanics.

Q: What muscles are found in the third layer of the foot?
A: Adductor hallucis (oblique and transverse heads), flexor hallucis brevis, and flexor digiti minimi brevis.
Related Pearl: The adductor hallucis stabilizes the first metatarsophalangeal joint during gait.

Q: What structures are in the fourth layer of the foot?
A: Four dorsal and three plantar interossei muscles, peroneus longus tendon, and long plantar ligament.
Related Pearl: Interossei muscles control toe abduction and adduction, critical for balance.

Q: How are the medial and lateral plantar nerves protected from puncture?
A: By the thick plantar aponeurosis and the thick first muscular layer (FDB, abductor hallucis, abductor digiti minimi).
Related Pearl: This protection reduces risk of nerve injury during plantar foot procedures.

Foot Compartments & Compartment Syndrome

Q: How many compartments are in the foot, including Manoli’s calcaneal compartment?
A: Nine compartments: medial, lateral, superficial, adductor, four interossei, and calcaneal.
Related Pearl: Recognizing all compartments is essential for comprehensive compartment syndrome decompression.

Q: Which muscles are in the medial compartment of the foot?
A: Abductor hallucis and flexor hallucis brevis.
Related Pearl: Medial compartment involvement can cause hallux valgus deformity if untreated.

Q: Which muscles are in the lateral compartment of the foot?
A: Abductor digiti minimi and flexor digiti minimi.
Related Pearl: Lateral compartment syndrome may cause clawing of the fifth toe.

Q: What muscles are in the superficial compartment?
A: Flexor digitorum brevis, distal tendons of flexor digitorum longus, and four lumbricals.
Related Pearl: Superficial compartment involvement affects toe flexion and gait.

Q: What muscle comprises the adductor compartment?
A: Adductor hallucis.
Related Pearl: Adductor hallucis contracture can contribute to metatarsalgia.

Q: What muscle is in the calcaneal compartment?
A: Quadratus plantae.
Related Pearl: Quadratus plantae contracture causes clawing by pulling on FDL tendons in compartment syndrome.

Q: What causes clawing in foot compartment syndrome?
A: Contracture of quadratus plantae pulling on flexor digitorum longus tendons.
Related Pearl: Early recognition and decompression prevent permanent deformity.

Q: What is the surgical technique for foot compartment decompression?
A: Two dorsal longitudinal incisions decompress interosseous compartments; one medial curved incision decompresses medial, superficial, lateral, adductor, and calcaneal compartments.
Related Pearl: This approach balances adequate decompression with minimizing soft tissue damage.

Q: What nerves must be protected during foot compartment decompression?
A: The lateral and medial plantar nerves, which run deep to flexor digitorum brevis between the first and second muscular layers.
Related Pearl: Injury causes plantar numbness and weakness in toe flexion.

Classic Clinical Notes

• Extensor digitorum brevis is innervated by the deep peroneal nerve.

• A complete peroneal nerve injury at the fibular head would leave sensation only along the plantar aspect of the foot (tibial nerve) and along the medial aspect of the foot (saphenous nerve – continuation of femoral nerve).

• Note that in cross section:
• In the anterior compartment the EHL is most posterior and lays along the IO membrane; tib ant lies medially against the tibia, and EDL lays more laterally.
• In the lateral compartment, peroneus brevis is deep to longus.
• In the deep posterior compartment, tib post lays along the IO membrane, FDL lays posteromedially, and FHL lays most laterally (interesting that it lays so laterally when it has to get over so medially – just remember that FHL has to lay laterally because the Harmon approach goes between peroneus brevis and FHL). The plantaris tendon lies posteromedially between soleus and gastrocs.

• Tib post inserts into the tarsal navicular.

• The spring ligament runs between the calcaneus and navicular and “props up” the talar head. It officially is called the plantar calcaneonavicular ligament – and because it has some elasticity, and because it receives the head of the talus, it is called the spring ligament.

• The structure most at risk with the anteromedial portal is the great saphenous nerve and saphenous vein. For the anterolateral portal, watch out for the superficial peroneal nerve. The tibialis anterior nerve and artery run medial to EHL up high, but at the ankle they lay just lateral to EHL, between EHL and EDC. (Note that EHL and TA are medial). To get an anterocentral portal, go through the EDC tendons – that way you know the artery is medial.

• The medial and lateral plantar nerves pass deep to the abductor hallucis and flexor digitorum brevis.

• Important reminder about the layers in the foot:
• Superficial – plantar aponeurosis with lateral cord (what rips off the base of 5th metatarsal)
• Layer 1: Abductor hallucis, Flexor digitorum brevis (big thick muscle, just under plantar aponeurosis), Abductor digiti minimi
• Layer 2: Quadratus plantae, Flexor digitorum longus tendons, Flexor hallucis longus tendon, Lumbricals (with flexor digitorum longus)
• Layer 3: Adductor hallucis – oblique and transverse bands, Flexor hallucis brevis (with two heads going into the sesamoids), Flexor digiti minimi brevis
• Layer 4: Interossei – 4 dorsal, 3 plantar, Peroneus longus, Long plantar ligament

• Note that the medial and lateral plantar nerves are protected from puncture by the thick plantar aponeurosis and the thick first layer (consisting of FDB, AbdH, AbdDM).

• Compartments of the Foot – for Compartment Syndrome:
• Medial: Abductor hallucis, Flexor hallucis brevis
• Lateral: Abductor digiti minimi, Flexor digiti minimi
• Superficial: Flexor digitorum brevis, Distal tendons of flexor digitorum longus, Four lumbricals
• Adductor: Adductor hallucis
• Four interosseous compartments
• Calcaneal: Quadratus plantae – this is what Manoli has described.

• There are 9 compartments in total (if you count Manoli’s calcaneal compartment). The superficial, lateral, and medial compartments run the length of the foot. The adductor and 4 interossei compartments are confined to the forefoot. The calcaneal compartment is a separate hindfoot/midfoot compartment consisting of the quadratus plantae.

• Manoli feels that the clawing from compartment syndrome is due to the contracture of quadratus – pulls on the flexor digitorum longus tendons.

• The described technique of decompressing the compartments is two dorsal longitudinal incisions to decompress the interosseous compartments, then a medial curved incision to decompress the medial, superficial, lateral, adductor, and calcaneal. Beware the lateral and medial plantar nerves that run deep to the flexor digitorum brevis, between the 1st and 2nd muscular layers of the foot. (1st layer: flexor digitorum brevis, abductor hallucis, abductor digiti minimi. 2nd layer: quadratus plantae, tendons of FDL, tendon of FHL, lumbricals).

Last Updated on January 25, 2026 by Christian Veillette