What are the knee compartments?

1. Lateral tibiofemoral joint
2. medial tibiofemoral joint
3. Patellofemoral joint

2 planes of motion

• Rarely occur without interaction from other joints of the LE
• About 2/3 of the muscles the cross the knee also cross the hip or the ankle

Stability ___.

soft tissue restraints rather than boney anatomy

Osteology: distal femur

• epi(condyle)= before/above
• intracondyle: groove/notch/
  • "separate" 2 condyle (perfect match 3 patella)

Osteology: proximal tibia & fibula

• proximal tibia: not imp, muscle attachments for biceps femoris (5% of forces)
• epicondlye eminence: attachment for PCL and ACL
• tibial tuberosity: attachment for quads
• flat shape = tina plateu

Osteology: patella

• 4-5mm of cartilage
• facets // seismod bone
• impede @ quad tendon

Arthrology: general considerations

• medial hip angulation @ 125 degrees\
• normal knee valgus: 170-175 degrees

Genu Valgum vs. Genu Varum

• genu valgum: "gum" bwt legs
• genu varum: bow legs // WITCH

Ligaments, fascia, and muscle table graph

• regions of capsule
  • anterior
  • lateral
  • posterior
  • posterior-lateral
  • medial

Arthrology: general considerations, ligaments

• knee injuries > hip injuries
  • rely on dynamic structures
• knee = intercapsuled + extra support (MCL, LCL, PC...)
  • pes anserius tendons + hams = muscular support+stability

Arthrology: fat pads

• synovial fluid: line inner surface, UP glide +slide,
• knee bursa: fat pad, assist with friction-prone areas (LOWER %)
  • quads+intrapatellar

Arthrology: tibiofemoral joint

• UP flexion+extension
• femur on slight concave tibia (somewhat flat)
• GOOD mvt @end ranges: tear soft tissues B4 bone damage

Arthrology: tib-fem, menisci

• Crescent-shaped fibrocartilage structure: deepens capsule/knee
  • "stadium shaped" = hard to slide around/excessive mvts
  • quads/popliteus/semimembranosus
• nutrients from diffusion: (red= more blood/white= none)

The menisci: an important job

• primary function: compression absorption + increase knee surface area
• medial side = prone to more injury b/c UP axial rotation (plant+twist_
• MENISCUS SURGERY NOT NEEDED
  • risks with surgery = can cause early arthritis

Osteokinematics: tibiofemoral joint

• hinge joint

Osteokinematics: flex/ext

• tibial turberostiy moves medial: cause tibial internal rotation
• concave condle makes axis move => change internal mvt arm of muscle
• knee extension = closed=packed
  • more stable + more force transfer

Osteokinematics: internal & external rotation

• internal rotation: femur shifts out
• external rotation: femur shifts in

Arthrokinematics of tibiofemoral joint

• tibial on femur (open chain)
  • concave on convex = SAME
  • anterior roll = anterior slide
• femur on the tibia (closed chain)
  • convex on concave = OPPOSITE
  • anterior roll = posterior slide

screw-home mechanism

• for full extension (w/ some Ext.R)
  • longer medial + PCL passive tension
• popliteus IR knee = unlocking knee

Arthrokinematics of axial rotation

• SPINNING

Medial & lateral collateral contributions

• 2 fiber groups
• goal: prevent valgus+valgum collapse AND some axial rotational prevention

Function of ligament and common mech. of injury chart

Anterior & posterior cruciate ligaments

The ACL

• knee extension:
  • quads pull up + tibia kicks up + femur want to roll up
    • => keeps ACL taut
  • KEY = quad strength
• QUADS: antagonist of ACL
• Tear ACL: UP translation, pull on tibia (rotate foward+slide forward)
• TEAR w/o pull: valgus, hyperextension, activate quad at flex/end range + valgus

Posterior cruciate ligament

• checks posterior slide of knee/tibia (knee flexion)
  • most taut
• tear PCL: tibial slides backward

The patellofemoral joint

• stable in boney aspect
  • stabilized by quad + patella wedge in notch
• medial +lateral femoral ligament

Patellofemoral joint kinematics

• closed chain: femur slide under fixed patella
• open chain: patella slide on fixed patella
• end range flexion: tibia contact points move in k.flex = only 1/3 pf patella contact w/ mvt
  
  • good b/c = UP knee flexion + slide (bend/glide)
• @90 degrees: doesn't move patella

Muscle function: extensors (aka the quads)

• 80% of torque produced by vastus m. + 20% from rectus femoris
  • connect to quad tendon
• extensor mechanism: quads + quad tendon + + patella
• 66% more than knee flexors
• isometric, concentric, eccentric

External torque demands

• open chain: (tibia on femur)
  
  • more extension -> most mvt arm -> most torque
  • straight knee = larger external
• closed chain: most mvt arm + knee flexion
  • miss squat at hole // not at top

Internal torque demands

• max in torque @45-70 degrees of knee flexion
  
  • least torque @ max knee flexion + extension
• most torque abilities
  • squat hardest @bottom + middle
  • squat easiest @top

The role of the patella

• functional length of external mnt arm of quad
  • longest @20-30 degrees flexion
• function: lengthens quad (spacer)
• HIGH compression force

Patellofemoral joint kinetics

• deep flexion: more compression (max @60-90 degrees)
  • contact area of patella + tibia @ same degrees
• knee over tore argument: force from knee + butt
• LOW knee bend = HIGH compression vector

Role of the quadriceps in patellar tracking

• slight lateral pull of quads (b/c vastus): pull patella more laterally
• Q angle: 13-15 degrees (normal)

WARNING: PATHOANATOMICS OUGHT NOT DICTATE CARE

• pathobiomechanics/anatomy is only a part of entire picture of a human
• procedures + paradigms NOT fully tested = adopted as standard care

Interconnectedness

• where genu valgum originate
  • Boney: hips, knees, tibias, ankles
  • weakness: hips, ankles

Muscle function: knee flexors/rotators

• all muscles that crosses posterior knee (NOT gastrocnemius) => flex + anterior rotate knee
  • closed chain

Control: tibial-on-femoral osteokinematics

• hamstrings: help control tib-fib kinematics, accelerating
  
  • different max torque from leverages: from force-length NOT moment arm)

Maximum torque: flexors

• force relationship
• Max leverage: 50-90 degrees
• Knee torque and flexion angle inverse relationship
  • HIGH knee flexion torque = LOW flexion angle (degrees)
  • LOW knee flexion torque = HIGH flexion angle