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Kinesiology of the Musculoskeletal System Chapter 13

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Controlled largely by large two joint muscles ... discs located within the knee joint ... Joint Reactive Force approximates 3X body weight with each step ... – PowerPoint PPT presentation

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Title: Kinesiology of the Musculoskeletal System Chapter 13


1
Kinesiology of the Musculoskeletal
SystemChapter 13
  • The Knee

2
Knee Joint
  • One of the largest joint complexes of the body
  • Condyloid joint tibiofemoral roll and slide
    kinematics
  • Patellofemoral joint planar joint
  • Positioned between two long bones increasing
    vulnerability to torque forces
  • Controlled largely by large two joint muscles
  • Stability based primarily on its soft tissue
    constraints
  • Moves in two planes
  • Sagittal Flexion/Extension
  • Horizontal Internal/External Rotation

3
Anatomical Structures of the Knee
  • Femoral Condyles medial and lateral
  • Articular Cartilage
  • Tibial Plateau
  • Patella
  • Menisci medial and lateral
  • Ligaments ACL, PCL, MCL, LCL
  • Musculotendinous structures
  • Fibular head
  • Joint Capsule

4
Anatomy of the Knee
5
Anatomy of Knee
6
Patella
  • Largest sesamoid bone in the body
  • Free floating bone attached chiefly by quadriceps
    tendon and patellar ligament
  • Chief function is to increase the IMA of knee
    extension mechanism
  • Undersurface articulates with the intercondylar
    region of the femur and has a thick articular
    cartilage layer to disperse large compression
    forces of this patellofemoral joint
  • Patellofemoral pain is one of the most common
    knee ailments in athletes and the general
    population

7
Tibiofemoral Patellofemoral Joints
8
Knee Joint Capsule
  • Fibrous capsule reinforced by muscles, tendons,
    ligaments and fascia
  • No bony block against hyperextension muscles and
    capsule limits hyperextension

9
Knee Alignment
  • Normal alignment is in slight genu valgum
    170-174 degrees due to angle of inclination of
    the femoral head
  • Excessive Genu Valgum lateral angle of knee is
    less than 170 degrees, aka Knock Knees
  • Genu Varum lateral angle of knee is greater
    than 180 degrees, aka Bow Legs
  • Longitudinal or Vertical axis of rotation line
    connecting femoral head with the center of the
    knee joint Mechanically links horizontal plane
    movements of the major lower limb joints
    horizontal plane movement of any lower limb joint
    can directly affect the other lower limb joints

Genu Valgum
Genu Varus
10
Menisci
  • Menisci crescent shaped fibrocartilagenous
    discs located within the knee joint
  • Medial C shaped Lateral O shaped
  • Loose ligamentous attachment to tibia and joint
    capsule allows menisci to pivot/slide during knee
    movement
  • Shock absorption reduces
  • compressive stress
  • Deepens articular surface
  • of tibia for femoral condyles
  • increases joint contact 3X
  • Guides femoral motion

11
Menisci (cont.)
  • Increases joint surface contact 3X
  • During walking, menisci deform peripherally with
    each step
  • Joint Reactive Force approximates 3X body weight
    with each step
  • Menisci support 50 of load across the knee
  • Removal of lateral meniscus increases peak
    contact pressures 230
  • Extreme compression (high impulse) can fracture
    menisci and underlying bone

12
Menisci (cont.)
  • Poorly vascularized
  • only outer edges
  • of the menisci
  • have a blood supply
  • Poor repair
  • Poor nerve supply
  • often non-painful

13
Cadaver Tibiofemoral Joint
14
Cadaver Menisci
15
Tibiofemoral Arthrokinematics
  • Flexion/Extension Internal/External rotation
  • Menisci follow tibia
  • Roll Slide

16
Tibiofemoral Flexion/Extension
  • Flexion to 130-140 degrees
  • Extension to 5-10 degrees of hyperextension
  • Axis of Rotation varies or migrates through F/E
    termed evolute alters IMAs and may have
    clinical and training implications

17
Tibiofemoral Internal/External Rotation
  • Axial rotation in the horizontal plane
  • Near zero degrees of I/E rotation with knee fully
    extended
  • Up to 50 degrees of total I/E rotation with knee
    in 90 degrees of flexion
  • External Internal 2 1
  • Tibial on Femoral
  • Femoral on Tibial

18
Tibiofemoral Internal/External Rotation
19
Femoral on Tibial Rotation
  • Femoral rotation on a relatively fixed tibia
  • Requires some
  • degree of knee
  • flexion
  • High level of
  • vulnerability
  • especially when
  • coupled with
  • muscular force
  • production

20
Screw Home Mechanism
  • 10 degrees of coupled external rotation during
    the final 30 degrees of knee extension
  • T on F Screw Home is more evident but F on T SHM
    does occur
  • SHM caused by
  • Shape of medial femoral condyle
  • Passive tension of the ACL as knee is extended
  • Lateral pull of the quadriceps muscle group

21
Active Flexion of the Knee
  • From full extension, the Screw Home Mechanism is
    reversed
  • Knee joint is unlocked by popliteus muscle
    creating knee flexion and internal rotation
  • T on F or F on T

22
Ligaments of the Knee
  • Medial Collateral Ligament (MCL) primarily
    checks valgus stress has attachment to meniscus
  • Lateral Collateral Ligament (LCL) primarily
    checks varus stress blends with biceps femoris
    tendon

MCL
LCL
23
Ligaments of the Knee (cont.)
  • Anterior Cruciate Ligament (ACL) primarily
    checks posterior to anterior shear forces
  • Posterior Cruciate Ligament (PCL) primarily
    checks anterior to posterior shear forces
  • AP and PA shear forces commonly seen in sagittal
    plane motion, i.e. walking, running, jumping,
    squatting

24
Ligaments of the Knee (cont.)
  • Acting together
  • ACL and PCL
  • limit extremes
  • of knee motions
  • in all directions
  • Intracapsular
  • Extrasynovial

25
ACL Injury
  • Most frequently injured ligament of the knee
    especially with high velocity stretch while
    ligament is under tension
  • Often seen in cutting
  • and jumping sports,
  • i.e. football, soccer,
  • skiing, volleyball,
  • basketball
  • Up to 80 of
  • ACL injuries are
  • non-contact injuries

26
PCL Injury
  • Slightly thicker and stronger
  • than ACL
  • Less vulnerable to injury
  • Injured due to hyperflexion falling on
    hyperflexed knee contact injury to proximal
    tibia with planted foot (dashboard injury)
    landing from a jump with slightly flexed knee or
    rapid descent into full squat

27
ACL / PCL Assessment
28
ACL Kinesiopathology
  • Partial or complete tear of the ACL will likely
    result in hamstring spasm in the short term or
    hamstring facilitation (increased activity) in
    the long term
  • Hamstring muscles can
  • help stabilize knee by limiting
  • anterior tibia translation on
  • the femur
  • Increased hamstring muscle
  • activity will Reciprocally Inhibit
  • the quadriceps
  • This reciprocal inhibition is
  • based on the same neurology as
  • the facilitation/inhibition found
  • in many faulty postural muscle
  • patterns

29
ACL Rehab
  • Early phase must limit tension on ACL
  • Avoid open chain T on F exercises through full
    ROM
  • Emphasize closed kinetic chain exercises loading
    quadriceps muscle in the final 45 degrees of F on
    T extension
  • Mini-squats, terminal knee extension exercises

30
T on F Extension
31
Muscular Function at the Knee
  • Knee Extensor Mechanism
  • Isometric Contraction stabilizes knee and
    patella
  • Eccentric Contraction decelerates the lower leg
    (ie. walking, running), absorbs shock, controls
    rate of descent of the bodys center of mass
    (i.e. sitting)
  • Concentric Contraction accelerates the tibia (T
    on F) or the femur (F on T) raise the bodys
    center of mass (i.e. standing up, jumping)

32
Knee Extensor Mechanism (cont.)
33
Patellofemoral Mechanics
  • Describes the position and movement of the
    patella within the inter-condylar groove
  • Patellofemoral joint compressive forces may
    reach 3.3X BW while climbing stairs or 7.8X BW
    during deep knee bends
  • Anatomical considerations (widening intercondylar
    groove, thickened articular cartilage, underlying
    soft tissue structures) help minimize the effect
    of these large compressive forces
  • Patellofemoral compressive forces increase as
    knee flexion increases, and as quadriceps force
    production increases

34
Patellofemoral Mechanics (cont.)
35
Patellofemoral Tracking
  • Describes the path taken by the patella through
    the intercondylar groove
  • Contributing structures include the overall line

  • of force of the

  • quadriceps group,

  • pull of the vastus

  • medialis oblique

  • (VMO), patellar

  • retinacular fibers,

  • ilitotibial band

36
Patellofemoral Tracking (cont.)
  • Aberrant or abnormal tracking can
  • lead to painful conditions including
  • patellofemoral pain, chondromalacia
  • patella, degenerative arthritis,
  • subluxing or dislocating patella

Dislocated Patella
37
Q Angle
  • The degree of lateral pull exerted by the
    quadriceps, on the patella
  • Formed between line representing the pull of the
    quadriceps (ASIS to patella) and a line
    connecting the tibial tuberosity with the patella
  • Female Average 15.8 degrees, Male 11.2 degrees
  • Contributing factors Width of pelvis degree of
    adduction of femur hip extensor and abductor
    strength patellar stability degree of tibial
    rotation foot, ankle stability degree of
    pronation

38
Knee Flexor / Rotator Mechanism
  • Except for the gastrocnemius, all muscles that
    cross the knee joint posteriorly function to flex
    rotate the knee (hamstrings, sartorius,
    gracilis, popliteus)
  • Medial hamstrings (semimembranosus and
    semitendinosus flex and internally rotate the
    knee
  • Lateral hamstrings (biceps femoris) flex and
    externally rotate the knee

39
Knee Flexor / Rotator Mechanism (cont.)
  • Flexor / Rotator muscles best perform their
    actions during walking and running, both
  • T on F F on T
  • T on F Flexor / Rotator muscles decelerate the
    tibia during walking or running
  • F on T stabilize and/or rotate knee during
    walking or running

40
References
  • Neumann, D. Kinesiology of the Musculoskeletal
    System. 2002. Human Kinetics.
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