Human Anatomy Week 7b - Knee, Popliteal Fossa, Leg (Transcripts)
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Questions and Answers

What is the prominent bony structure referred to as the 'shin'?

  • Anterior border of the tibia (correct)
  • Medial malleolus
  • Soleal line
  • Tibial tuberosity

    • Which bone is located laterally in the leg?

  • Fibula (correct)
  • Tibia
  • Medial malleolus
  • Tibial tuberosity

    • What anatomical landmark acts as the attachment point for the patellar tendon?

  • Lateral malleolus
  • Anterior border of the tibia
  • Soleal line
  • Tibial tuberosity (correct)

    • What divides the muscle attachments on the posterior tibia?

    <p>Soleal line</p> Signup and view all the answers

    Which bony structure is located on the distal portion of the tibia?

    <p>Medial malleolus</p> Signup and view all the answers

    What is the primary function of the interosseous membrane in the leg?

    <p>To divide the leg into compartments and provide stability between bones</p> Signup and view all the answers

    Which compartment of the leg contains the dorsiflexors?

    <p>Anterior compartment</p> Signup and view all the answers

    What is the primary role of the flexor retinacula?

    <p>To hold down key ligaments and flexor tendons at the ankle</p> Signup and view all the answers

    Which muscles are primarily found in the superficial posterior compartment?

    <p>Gastrocnemius and soleus</p> Signup and view all the answers

    How does the crural fascia relate to the thigh's fascia?

    <p>It is a continuation of the fascia lata</p> Signup and view all the answers

    What is the primary shape contributor to the superficial posterior compartment of the leg?

    <p>Gastroc</p> Signup and view all the answers

    Which statement correctly describes the action of the soleus muscle?

    <p>It is involved in ankle plantar flexion regardless of knee position.</p> Signup and view all the answers

    What is a notable characteristic of the plantaris muscle?

    <p>Its muscle belly is often absent in some individuals.</p> Signup and view all the answers

    Which nerve innervates the muscles of the superficial posterior compartment?

    <p>Tibial nerve</p> Signup and view all the answers

    Which of the following statements about the gastrocnemius muscle is true?

    <p>It attaches via the calcaneal tendon to the calcaneus.</p> Signup and view all the answers

    Study Notes

    Superficial Posterior Compartment

    • Muscles: Gastrocnemius, Soleus, Plantaris
    • Insertion: Posterior surface of calcaneus via calcaneal/Achilles tendon
    • Innervation: Tibial nerve (S1, S2)
    • Action: Plantar flex the ankle
    • Gastrocnemius: Also crosses knee joint; more prominent when knee is extended.
    • Soleus: Does not cross knee joint, action is the same whether knee is flexed or extended.
    • Plantaris: Muscle is small/variable; tendon may rupture, creating a muscle knot.
    • Clinical Considerations: Achilles tendinitis, Deep vein thrombosis (DVT)
      • Ankle pumps are helpful for DVT

    Deep Posterior Compartment

    • Muscles: Popliteus, Tibialis posterior, Flexor digitorum longus, Flexor hallucis longus
    • Innervation: Tibial nerve (S1, S2)
    • Popliteus: Functions at the knee.
    • Other Muscles: Plantar flex the ankle, invert the foot, and affect toe movement.
    • Tibialis posterior: Wedged against interosseous membrane; runs along posterior tibia.
    • Flexor digitorum longus: Runs along medial side of posterior tibia.
    • Flexor hallucis longus: Runs along lateral side.
    • All tendons run together around medial malleolus, forming a mnemonic "Tom, Dick, and Harry" (tibialis posterior, flexor digitorum longus, flexor hallucis longus).

    Compartments of Leg

    • Anterior compartment: Dorsiflexors (pull toe and ankle upward)
    • Lateral compartment: Muscles attach to fibula; Everters
    • Posterior compartment: Plantar flexors
      • Superficial muscles: Gastrocnemius and Soleus.
      • Deep muscles: Long toe flexors and tibialis posterior.
    • Intermuscular septa: Separate compartments of the leg.
    • Interosseous membrane: Separates anterior from deep posterior compartments.
    • Transverse septum: Separates deep posterior and superficial posterior compartments.
    • Muscles in compartments are compartmentalized, so the tibial nerve innervates all the muscles in each compartment.

    Posterior Compartment Muscles

    • Popliteus:
      • Superior most muscle of the posterior compartment
      • Attaches to the lateral condyle of the femur and the posterior tibia superior to the soleal line
      • Innervated by the tibial nerve (L4-S1)
      • Medially rotates the tibia during knee flexion
    • Flexor Hallucis Longus:
      • Attaches to the posterior fibula
      • Inserts on the base of the distal phalanx of the big toe
      • Flexes the big toe at all joints
      • Contributes to plantar flexion and arch support
    • Flexor Digitorum Longus:
      • Attaches to the posterior surface of the tibia
      • Inserts on the distal phalanges of the lateral four toes (toes 2-5)
      • Flexes the lateral four toes at all joints
      • Contributes to plantar flexion and arch support
      • Innervated by the tibial nerve (S2-S3)
    • Tibialis Posterior:
      • Deepest of all the posterior compartment muscles
      • Primary attachment is to the interosseous membrane between tibia and fibula
      • Inserts on the tuberosity of the navicular, cuneiforms, cuboid, and bases of middle three metatarsals
      • Plays a major role in arch support
      • Plantar flexes and inverts the foot
      • Innervated by the tibial nerve (L4-L5)

    Posterior Compartment Neurovascular structures

    • Tibial Nerve:
      • Innervates all muscles of the posterior compartment
    • Posterior Tibial Artery:
      • Supplies blood to all muscles of the posterior compartment
    • Tom, Dick, and Harry:
      • Refers to the tendons of tibialis posterior, flexor digitorum longus, and flexor hallucis longus as they pass behind the medial malleolus
      • The posterior tibial artery and tibial nerve lie between the flexor digitorum longus and flexor hallucis longus tendons.

    Anterior Compartment Muscles

    • Tibialis Anterior:
      • Largest and most superficial anterior compartment muscle
      • Attaches to the superior lateral border of the tibia
      • Inserts on the first cuneiform and first metatarsal
      • Dorsiflexes and inverts the foot
      • Innervated by the deep fibular nerve (L4-L5)
    • Extensor Digitorum Longus:
      • Attaches to the anteromedial surface of the fibula
      • Inserts on the distal phalanges of toes 2-5
      • Extends toes 2-5 and contributes to dorsiflexion of the foot
      • Innervated by the deep fibular nerve (L4-L5)
    • Extensor Hallucis Longus:
      • Deepest muscle of the anterior compartment
      • Attaches to the anterior aspect of the interosseous membrane
      • Inserts on the distal phalanx of the big toe
      • Extends the big toe and contributes to dorsiflexion of the foot
      • Innervated by the deep fibular nerve (L4-L5)
    • Fibularis Tertius:
      • Small muscle, not present in all individuals
      • May arise from the lateral aspect of the extensor digitorum longus
      • Inserts on the base of the 5th metatarsal
      • Dorsiflexes and everts the foot
      • Innervated by the deep fibular nerve (L4-L5)

    Dorsum of the Foot Muscles

    • Extensor Digitorum Brevis:
      • Superficial muscle on the dorsum of the foot
      • Extends the toes 2-4
      • Innervated by the deep fibular nerve (L5-S1)
    • Extensor Hallucis Brevis:
      • Medial to the extensor digitorum brevis
      • Extends the big toe
      • Innervated by the deep fibular nerve (L5-S1)

    Anterior Compartment Neurovascular Structures

    • ** Deep Fibular Nerve:**
      • Innervates all muscles of the anterior compartment
    • Anterior Tibial Artery:
      • Supplies blood to all muscles of the anterior compartment

    Arterial Supply of the Leg

    • The posterior tibial, anterior tibial, and fibular arteries are the three main arteries supplying the leg
    • All of these arteries originate from the popliteal artery, which is an extension of the femoral artery
    • The anterior tibial artery travels within the anterior compartment and supplies it
    • The posterior tibial artery travels within the deep posterior compartment and supplies both posterior compartments
    • The fibular artery travels within the deep posterior compartment but supplies the lateral compartment
    • The tibial artery crosses the anterior ankle joint and changes its name to the dorsalis pedis artery

    Superficial Veins of the Leg

    • The small saphenous vein runs up the posterior lower leg superficial to the gastrocnemius muscle
    • The small saphenous vein joins the popliteal vein in the popliteal fossa
    • The great saphenous vein runs from the medial ankle, up the medial leg and thigh, and joins the femoral vein in the femoral triangle

    Lymphatics of the Leg

    • Superficial lymphatics primarily follow the course of the superficial veins
    • There is a posterior lymphatic flow that comes up the back of the leg and joins into deeper circulation at the popliteal fossa
    • There is a medial lymphatic flow that comes up the medial leg and thigh, joining into deeper circulation at the femoral triangle

    Innervation of the Leg

    • All of the nerves of the leg come from the sciatic nerve, branching from the sacral plexus
    • The sciatic nerve splits into the tibial nerve continuing inferiorly and the common fibular nerve continuing laterally
    • The tibial nerve continues inferiorly from the popliteal fossa, running deep in the posterior compartment and serving both deep and superficial posterior compartments
    • The tibial nerve continues around the medial malleolus and enters the plantar foot
    • The common fibular nerve travels around the head and neck of the fibula and splits into the deep fibular nerve and the superficial fibular nerve
    • The deep fibular nerve serves the muscles in the anterior compartment
    • The superficial fibular nerve travels in the lateral compartment and innervates its muscles

    Neurovascular Bundles of the Leg

    • The posterior compartment is innervated by the tibial nerve and supplied by the posterior tibial artery. The fibular artery also runs in this compartment, but supplies the lateral compartment
    • The anterior compartment is innervated by the deep fibular nerve and supplied by the anterior tibial artery
    • The lateral compartment is innervated by the superficial fibular nerve and supplied by the fibular artery, despite the artery being located within the posterior compartment

    Sensory Distribution of the Leg

    • The saphenous nerve, a continuation of the femoral nerve, is responsible for sensation in the anteromedial leg
    • The sural nerve, branching from the sciatic nerve, innervates the posterior and lateral leg

    Lateral Compartment of the Leg

    • The lateral compartment of the leg contains the fibularis longus and fibularis brevis muscles
    • Both muscles primarily evert the foot and aid with plantarflexion
    • The muscles are innervated by the superficial fibular nerve, which emerges superficial around two-thirds of the way down the lateral compartment
    • The lateral compartment's blood supply comes from the fibular artery located in the deep posterior compartment
    • The fibularis longus is a longer muscle and runs behind the lateral malleolus, across the plantar foot, attaching to the first metatarsal and first cuneiform
    • The tendon of the fibularis brevis runs behind the lateral malleolus but attaches to the tuberosity of the base of the fifth metatarsal

    Anterior Compartment of the Leg

    • The anterior compartment muscles are responsible for dorsiflexion of the foot
    • The compartment is innervated by the deep fibular nerve
    • The deep fibular nerve continues down the leg and provides sensory innervation to the dorsal foot between the toes
    • The compartment is supplied by the anterior tibial artery, which continues across the ankle joint as the dorsalis pedis artery

    Posterior Compartments of the Leg

    • There are superficial and deep posterior compartments
    • Both compartments are innervated by the tibial nerve
    • They are supplied by the posterior tibial artery and fibular artery

    Clinical Considerations:

    • Anterior shin splints are a common complaint in runners, caused by overuse or improper running technique
    • Compartment syndrome is a condition where swelling or bleeding within a compartment restricts blood flow and nerve function, potentially leading to compartment syndrome
    • Foot drop is a condition where the deep fibular nerve is compromised leading to an inability to dorsiflex the foot
    • Venous stasis ulcers are a common type of wound that can occur at the posterior calf or, more commonly, around the medial ankle, due to a build-up of fluid from poor venous return### Tibiofibular Joints
    • There are three tibiofibular joints: proximal, middle, and distal
    • All three joints work together with the ankle joint, but the proximal joint is close to the knee.
    • The proximal tibiofibular joint is a gliding planar joint with a facet on the tibia and fibula.
    • The proximal tibiofibular joint is reinforced by ligaments and is close to the common fibular nerve, biceps femoris tendon, and lateral collateral ligament of the knee.
    • A limitation in gliding of the fibula at the proximal tibiofibular joint can impact ankle movement.

    Middle Tibiofibular Joint

    • The middle tibiofibular joint is a syndesmosis joint, where the tibia and fibula are held together by the interosseous membrane.
    • It has no synovial joint.
    • The fibers in the interosseous membrane help with the pull between the bones and disperse forces.

    Distal Tibiofibular Joint

    • The distal tibiofibular joint has a facet on the distal fibula and distal tibia where the bones articulate.
    • It is considered a syndesmosis joint by most sources, but may have some gliding structure.
    • It has ligaments such as anterior, posterior, and interosseous ligaments.

    Ankle Joint Function

    • The ankle joint functions with the tibiofibular joints, and the movement of the talus (ankle bone) can influence the tibiofibular joints.
    • Dorsiflexion (moving the dorsum of the foot up) can cause the talus to wedge the tibia and fibula, creating pressure on these joints.
    • This pressure requires some "give" from the tibiofibular joints, often with slight gliding of the fibula during dorsiflexion.
    • Scarring or immobility in the tibiofibular joints can limit ankle range of motion.
    • A high ankle sprain involves injury to the tibiofibular ligaments and the interosseous membrane.

    Distal Tibiofibular Joint Anatomy

    • The distal tibiofibular joint is a small space where the tibia and fibula are closely connected.
    • The talus (ankle bone) fits into this space creating a "mortise" structure vital for the ankle joint.
    • This joint space has ligaments across the anterior, posterior, and interosseous spaces.

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