Recording-2025-07-23T16:25:27.366Z

Femur (Thigh Bone)

• Longest & heaviest bone in the body; transmits body-weight from pelvis to lower limb.
• Natural anterior bow:
  • Distributes \text{stress} \;\&\; \text{strain} created by gravity.
  • Increases resistance to bending loads.
• Key surface features (proximal → distal):
  • Head & neck (lecture mentions earlier material on inclination / (retro-, ante-)version).
  • Shaft largely smooth except:
  • Linea aspera (posterior rough line) – major muscular origin/insertion site.
  • Distal extremity:
  • Medial & lateral epicondyles – medial more prominent.
  • Adductor tubercle – superior to medial epicondyle; landmark for adductor insertions & palpation.
  • Femoral condyles – form inferior/distal articular surface; sit on tibial condyles + menisci.
  • Trochlear groove (patellar surface) – anterior dip between condyles; patella tracks here (“train-track” metaphor).

Tibia (Shin Bone)

• 2nd largest bone in body; primary weight-bearing element of leg.
• Proximal end = tibial condyles (medial & lateral) → widen into tibial plateau.
• Gerdy’s tubercle (antero-lateral): IT-band insertion; clinical relevance in IT-band friction syndrome.
• Sequence of load transmission: pelvis → femur → tibial plateau → menisci → tibia → foot.

Fibula

• Posterolateral to tibia; not part of the knee joint articulation.
• Minimal weight-bearing; mainly muscle attachments.
  • Thus isolated fibular fractures may allow ambulation (example: basketball player unknowingly played 4 weeks on fractured fibula; pain due to muscle pull, not load).

Patella

• Sesamoid bone embedded in quadriceps tendon → continues as patellar tendon to tibial tuberosity.
• Function: displaces tendon anteriorly, increases moment arm → larger knee-extension torque.
• Surfaces / poles:
  • Base (superior & flat).
  • Apex (inferior, pointed).
• Posterior surface covered by thick articular cartilage; divided by vertical ridge into facets:
  • Lateral facet.
  • Medial facet, further subdivided into:
  • Medial facet proper.
  • Odd facet – first area to degenerate (highest load in deep flexion).
• Patellar tracking: slides 7!\text{–}!8\,\text{cm} superiorly from full flexion → full extension.

Q-Angle & Frontal Plane Alignment

• Definition:
  • Line 1: ASIS → mid-patella.
  • Line 2: mid-patella → tibial tuberosity.
  • Q=\text{angle between lines}; quantifies valgus load on knee.
• Normal values:
  • Men: 10^{\circ}!\text{–}!14^{\circ}
  • Women: 15^{\circ}!\text{–}!17^{\circ} (wider pelvis for parturition).
• Abnormal terms:
  • Q>17^{\circ} → genu valgum (“knock-knee”).
  • Q<10^{\circ} → genu varum (“bow-leg”).
  • Genu recurvatum – hyper-extension past 0^{\circ}.
• Clinical relevance:
  • Excessive valgus ↑ lateral meniscus stress, ↑ patellofemoral dysfunction.
  • Excessive varus ↑ medial meniscus load.
  • Osteotomy sometimes performed in conjunction with ACL/meniscus surgery to normalize Q-angle.

Screw-Home Mechanism (Automatic Rotation)

• Locking / unlocking rotation coupling with flex-ext.
• Open-kinetic-chain (OKC): tibia moves on fixed femur.
  • Terminal extension: tibia externally rotates \approx20^{\circ} (locks knee; most ligamentous stability).
  • Initial flexion: tibia internally rotates \approx20^{\circ} (unlocks); chiefly by popliteus.
• Closed-kinetic-chain (CKC): femur moves on fixed tibia.
  • Reverse rotations (femur IR in extension, ER in flexion).
• Convex–concave rule:
  • OKC: concave tibial plateau rolls & glides same direction.
  • CKC: convex femoral condyles roll & glide opposite directions (posterior roll + anterior glide during squat descent, etc.).

Patellofemoral Contact Progression

• Deep-flexion tasks (e.g., lineman stance, heavy squats) concentrate force on odd facet → early cartilage wear.

Musculature Affecting the Knee

Quadriceps (Anterior Compartment)

• Common themes: femoral nerve innervation; primary knee extension.

Pes Anserinus Group (Anterior-medial Tibia)

Mnemonic “Sergeant Pes”: SGT = Sartorius, Gracilis, semiTendinosus.

Hamstrings (Posterior Compartment)

• “Tent over Mountain” mnemonic: semiTendinosus tendon superficial to semiMembranosus.

Popliteus

• O: Lat. femoral condyle (post.)
• I: Postero-medial tibia.
• Actions: Unlocks knee (IR tibia in OKC / ER femur in CKC), weak knee flexor.
• Nerve: Tibial.

Gastrocnemius (crosses knee & ankle)

• Not detailed in transcript; acts as knee flexor, plantarflexor.

Ligamentous & Capsular Structures

Extra-Articular

• MCL (TCL): broad, band-like; med femoral epicondyle → med tibial condyle; deep fibers blend with medial meniscus.
  • Resists valgus stress.
  • Tight in extension; lax in flexion/internal rot.
  • Injury may accompany medial meniscus tear → part of “unhappy triad” (ACL + MCL + medial meniscus).
• LCL (FCL): cord-like; lat femoral epicondyle → fibular head; no meniscal attachment.
  • Resists varus stress.
  • Palpable “guitar string”.

Intra-Articular Cruciate Ligaments

• ACL
  • Prox: med surface of lateral femoral condyle.
  • Dist: anterior intercondylar eminence of tibia.
  • Bundles: anteromedial (tight flexion), posterolateral (tight extension), intermediate.
  • Prevents:
  • OKC: anterior tibial translation.
  • CKC: posterior femoral translation.
  • Tests: Lachman (tibia ant glide), Lever/ Lelli’s (femur post translation), anterior drawer.
• PCL
  • Prox: lat surface of medial femoral condyle.
  • Dist: posterior tibial plateau.
  • Prevents:
  • OKC: posterior tibial translation.
  • CKC: anterior femoral translation.
  • Tests: Posterior drawer, posterior sag sign.

Patellar Restraint

• MPFL: adductor tubercle / VMO→ superomedial patella.
  • Primary passive check to lateral patellar displacement.
  • Torn in patellar dislocation events (video example: AT extends knee, quad contraction pops patella back).

Posterolateral Complex

• Arcuate ligament, posterior capsule, LCL, fabellofibular ligament (if sesamoid fabella present), part of PCL, popliteus tendon.
• Provide posterolateral stability; often involved with cruciate injuries.

Posteromedial Stabilizers

• Oblique popliteal ligament (expansion of semimembranosus), posteromedial capsule, etc.

Menisci

• Fibrocartilaginous C-shaped wedges on tibial plateau; deepen socket, distribute load, absorb shock.
• Medial meniscus: larger, less mobile, attached to MCL → higher tear rate.
• Lateral meniscus: smaller, nearly circular, no LCL attachment.
• Total meniscectomy greatly concentrates contact stress → early osteoarthritis (image in lecture).

Bursa Around Knee (names only)

• Prepatellar, infrapatellar (superficial & deep), suprapatellar, pes anserine, gastrocnemio-semimembranosus, etc.—clinically relevant for bursitis diagnosis.

Neurovascular Supply

Arteries

• External iliac → \text{inguinal lig.} → femoral → popliteal (after adductor hiatus).
• Popliteal → anterior & posterior tibial arteries.
• Genicular anastomosis: 5 genicular branches (sup lat/med, mid, inf lat/med) + ant tibial recurrent, descending genicular, descending branch of lateral circumflex femoral.
  • Ensures perfusion during deep knee flexion when popliteal artery kinked.

Veins

• Mirror arteries; popliteal vein → femoral vein above adductor hiatus.

Nerves

• Femoral nerve (anter