Lower Limb: Knee and Leg Region – Review Flashcards

Osteology of Knee Region

• Bones involved
• Femur – distal condyles, epicondyles, intercondylar notch, adductor tubercle, terminal sulcus, Grant’s notch
• Tibia – largest leg bone; medial; tibial plateau; intercondylar eminence; tibial & anterolateral (Gerdy’s) tubercles
• Patella – largest sesamoid, embedded in quadriceps tendon; posterior articular facets (medial, lateral, odd)
• Fibula – slender, lateral; proximal head is attachment for muscles/ligaments; common fibular nerve winds around neck → neuropathy risk
• Fabella – sesamoid in lateral gastrocnemius; inflammation = fabellitis

Knee Articulations

• Tibiofemoral Joint (TFJ)
• Femoral condyles ↔ tibial plateau; menisci interposed
• Movements: flexion/extension, IR/ER of tibia
• Patellofemoral Joint (PFJ)
• Patella ↔ trochlear groove; extensor mechanism linkage
• Superior/Proximal Tibiofibular Joint (STFJ/PTFJ)
• Tibia ↔ fibular head; stabilised by ant/post ligs of fibular head; independent of knee motion; may sublux

Menisci

• Medial – “C”-shaped; attached to deep MCL & semimembranosus → higher injury rate
• Lateral – “O”-shaped; no capsular/muscular attachments → more mobile
• Functions: shock absorption, joint congruence, load distribution; poor vascularity: innermost avascular, outermost vascular → peripheral tears heal better
• Typical tears: bucket-handle, radial, flap, degenerative

Capsuloligamentous Support

• Joint capsule – fibrous outer, synovial inner; reinforced ant/lat/med/post by ligaments & tendons
• Extracapsular ligaments
• Lateral (Fibular) Collateral Lig. (LCL) – lat epicondyle → fibular head; resists varus (adduction);
closely related to biceps femoris tendon
• Medial (Tibial) Collateral Lig. (MCL) – superficial & deep layers; med epicondyle → tibia (~7\,\text{cm}) below joint; deep layer blends with medial meniscus; resists valgus (abduction)
• Anterolateral Lig. (ALL) – lat femur → anterolateral tibia; 83\%!{-}!100\% incidence; controls tibial IR; injury correlated with Segond fracture (bony avulsion)
• Oblique Popliteal Lig. – extension of semimembranosus; limits ER & hyperextension
• Arcuate Lig. – two limbs from fibular head to femur & posterior tibia; part of posterolateral corner stability
• Intra-articular ligaments
• Anterior Cruciate Lig. (ACL) – anteromedial tibia → posterolateral femoral condyle; multi-bundle fan; primary restraint to anterior tibial translation; some fibres taut in all positions; stretch tolerance 8\text{–}10\%
• Posterior Cruciate Lig. (PCL) – posterolateral tibial spine → anteromedial femoral condyle; resists posterior tibial translation esp. in flexion; taut throughout ROM
• Transverse Lig. – connects anterior horns of menisci

Muscle Groups Crossing Knee

• Quadriceps (RF, VL, VM, VI) – knee extension, patellar tracking
• Hamstrings (BF long/short, ST, SM) – knee flexion, tibial rotation
• Pes Anserinus – Sartorius (most ant), Gracilis, Semitendinosus (most post); common insertion on medial tibia; add medial stability
• Popliteal Fossa Muscles
• Popliteus – unlocks knee (CKC femoral ER / OKC tibial IR)
• Plantaris – small, weak PF & knee flexor; long tendon useful for grafts
• Gastrocnemius (med & lat heads) – knee flexor, powerful PF
• Misc
• Articularis Genu – lifts suprapatellar bursa during extension
• Iliotibial Band – multiple attachments (Kaplan fibres, patellar insertion, lateral intermuscular septum); contributes to lateral knee pain & tracking issues

Vascular Supply Around Knee

• Genicular anastomosis: descending branch of lateral circumflex femoral, descending genicular, superior medial/lateral, inferior medial/lateral, middle genicular (all off popliteal)
• Clinical: collateral flow during popliteal obstruction; surgical planning (TKA)

Osteology of the Leg (Distal to Knee)

• Tibia
• Triangular shaft: anterior “shin”, medial, lateral (interosseous)
• Posterior: soleal line (soleus origin), groove for tibialis posterior & FDL
• Distal: medial malleolus articulates with talus; lateral surface has ant tibiofibular lig.
• Fibula
• Bears \approx5\% BW; major role: muscular attachment & lateral malleolus forming mortise
• Distal tibiofibular syndesmosis reinforced by ant/post tibiofibular ligs

Leg Compartments Overview

• Anterior – DF & inversion; deep fibular n.; anterior tibial a.
• Lateral – eversion; superficial fibular n.; perforators from fibular a.
• Superficial Posterior – PF; tibial n.; posterior tibial a. (in deep layer)
• Deep Posterior – PF & inversion; tibial n.; posterior tibial & fibular a.

Anterior Compartment Muscles

• Tibialis Anterior – lat tibia → 1st MT & medial cuneiform; DF + inversion
• Extensor Hallucis Longus – med fibula → distal phalanx hallux; toe ext, DF, inversion assist
• Extensor Digitorum Longus – lat condyle tibia + fibula → middle/distal phalanges digits 2\text{–}5; toe ext + DF
• Fibularis Tertius – distal fibula → base 5th MT; DF + eversion (only fibularis that DF)
• Blood: anterior tibial a. (+ recurrent branches)
• Nerve: deep fibular n. (branch of common fibular after split within peroneus longus)

Lateral Compartment Muscles

• Fibularis Longus – head & sup 2/3 fibula → plantar 1st MT & medial cuneiform; eversion + weak PF; supports transverse arch
• Fibularis Brevis – distal 2/3 fibula → tuberosity base 5th MT; eversion + weak PF
• Blood: perforators from fibular a.
• Nerve: superficial fibular n.; also provides cutaneous dorsolateral foot sensation

Superficial Posterior Compartment

• Gastrocnemius – femoral condyles → calcaneus via Achilles; PF (knee ext bias), knee flex
• Soleus – fibular head + tibial soleal line → Achilles; primary PF when knee flexed
• Plantaris – lat supracondylar femur → Achilles; weak PF/knee flex; tendon grafts
• Blood/Nerve: none within, but supplied by posterior tibial a. & tibial n. running in deep layer just anterior to transverse septum

Deep Posterior Compartment

• Popliteus – lat femoral condyle → post tibia; unlocks knee
• Tibialis Posterior – IO membrane + tib/fib → navicular tuberosity + midfoot; PF + inversion; arch support
• Flexor Digitorum Longus – post tibia → distal phalanges digits 2\text{–}5; toe flex, PF, arch support
• Flexor Hallucis Longus – distal fibula → distal phalanx hallux; toe flex, PF, arch support
• Vessels: posterior tibial a. (+ fibular a.)
• Nerve: tibial n.
• Tarsal tunnel order (ant → post): Tibialis posterior, Flexor digitorum longus, posterior tibial vein, posterior tibial artery, tibial nerve, Flexor hallucis longus ("Tom, Dick, vAN, Harry")

Neurovascular Summaries

• Femoral n. – anterior thigh, sensory ant/med leg via saphenous branch
• Obturator n. – medial thigh motor/sensory
• Sciatic n. – splits tibial + common fibular; posterior thigh motor
• Tibial n. – posterior leg & plantar foot motor; sural sensory via med sural cutaneous
• Common Fibular n. – wraps fibular neck (injury risk); splits superficial + deep branches controlling eversion & DF respectively; supplies dorsum foot sensation
• Segmental Innervation Highlights
• Hip flexion L!2!–!L!3, extension L!4!–!S!1
• Knee flexion L!5!–!S1, extension L!3!–!L4
• Ankle DF L!4!–!L5, PF S!1!–!S2
• Foot inversion L!4!–!L5, eversion L!5!–!S!1
• Dermatomes (Keegan & Garrett map) – note overlap; autonomous zones differ from peripheral nerve fields