Lecture 5 (revised).docx

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Kinesiology&Physical Education
EDKP 206
David J Pearsall

2/21/2013 2:00:00 PM Knee tibiofemoral and patellofemoral  Femur  Tibia  Patella Superior tibofibular  Tibia  Fibular  Femur (distal)  Angled from the vertical- medially  Medial and lateral condyles o Articular with tibia  Patella surface o Inferior surface o Articulates with the patella  Patella articulates with the anterior/interior surfaces of condyles  Condyle differences o Medial: articulating surface is longer anterior/posterior  Screw home mechanism o Lateral: further anterior projection  Prevents lateral patella dislocation Tibia (proximal)  Medial tibial plateau > lateral tibial plateau o Increased loading on the MEDIAL side o Helps decrease stress (= force/area)  Intercondylar space is where cruciate ligaments attach  Tibial tuberosity = attachment of patellar tendon Meniscus  Fibrocartilage discs  Wedge shaped  Located b/w femur and tibia  Has some blood supply o on periphery (outside of meniscus) o will diminish with age  increased risk of injury o this region (vascular zone) is the easiest meniscal area to repair o menisctomy = removal of meniscus (not typically done now)  Function o Primary: increase contact (~2x) area b/w tibia and femur to decrease stress b/w femur and tibia o Other functions  Shock absorption  Joint stabilization  Joint lubrication  Tears = meniscal lesions o Will cause clicking and locking of joints  Caused by shear forces produced during rotary motions b/w femur and tibia 2/21/2013 2:00:00 PM fModified hing joint – 2 degrees of freedom (DOF)  Flexion/extension (transverse axis/sagittal motion) o Flexion: lateral rotation of FEMUR WRT TIBIA  Femoral abduction WRT tibia  Posterior translation of contact point o Extension: medial rotation of FEMUR WRT TIBIA  Femoral adduction WRT tibia  Anterior translation of contact point  Medial/lateral rotation (longitudinal axis) o Keeping femur static you move the toe in and out Some say 6 DOF  Conjucnt rotation and translation Note: closed chain activity – foot on the ground Open chain activity – foot in the air Knee ROM  Flexion ~140 o o  Extension ~ 0  External (lateral) rotation ~ 45 o o  Internal (medial) rotation ~ 30  Abduction/adduction few degrees Sagittal motion- daily living degree of knee flexion  Walking: 67  Sit-stand (normal chair): 99  Sit – stand (low chair): 105  Stairs: 99  Out of bath: 138  Knee arthoplasty (replacement) o We try to give the individual at least 100 degrees of flexion so they can perform regular activities (walking, stairs, standing from chair) 2/21/2013 2:00:00 PM 0 – heel strike  knee bends (some flexion) 0-60- stance phase  extension: straighten support leg to facilitate swing of leg 60-80: swing phase  knee is flexed to facilitate swing (so toes don’t hit the ground) 80-100: heel strike  extension of knee as your foot is aiming for the ground Knee alignment  Depends on alignment of hips, ankle, and foot joint  Mechnical axis angle o Axis 1: center of femoral head to center of knee o Axis 2: center of ankle to center of knee o Mechanical angle = angle b/w axis 1 & 2 0  Normal = ~2 varus (medial)  Note: anatomical angle = along shaft of femur & shaft of tibia o Gives information about lower limb alignment  Varus o Distal segment (i.e. tibia) deviates medially on proximal segment (femur)  Genuvarus – bow legged  Angle b/w proximal and distal segments opens medially  Associated with degenerative joint disease  Increased lever arm for GRF  Genu recurvatum- hyperextension of the knee  In the sagittal plane, the vertically aligned femur and tibia form an angle of 180 degrees naturally  In this disease, the angle is >18- degrees  Valgus o Distal segment (i.e. tibia) deviates laterally on proximal segment (femur)  Genuvalgus – knocked knees (Knees touch)  Angle b/w proximal and distal segments opens laterally o Small GRF lever arm  lever arm of GRF causes a knee adduction moment which pulls femur inwards o The inward movement is greater in varus legs due to greater length of GRF moment arm  this causes a greater stress on the medial compartment of leg  Knee osteoarthritis (OA) o Deterioration of joint tissue (bone & cartilage) o Varus alignment- increased risk of medial compartment knee OA development and progression o Valgus alignment- increased risk of lateral compartment knee OA progression  Alignment correction o High tibial osteotomy  Correct limb aligment changes the mechanical axis angle  Less so in varus  Bow legged= swing out tibia to more straight  Valgus  Knock kneed: swing tibia out  This will serve to decrease medial compartment loading and slow knee OA disease progression o After surgery:  44% improvement in pain  34% improvement in function   open circles- start high go to low: knee addcution moment showing less medial compartment loading  after surgery: red line show sthe decrease in medial compartment loading Joint Surface Motion 2/21/2013 2:00:00 PM Knee flexion: contact b/w femur and tibia moves posteriorly on tibia Knee extension: contact b/w femur and tibia moves anteriorly on tibia Screw home mechanism (SEEN DURING EXTENSION during last 15 degrees of movement!!)  Open kinetic chain (foot off ground) o Lateral (external) rotation of tibia WRT (on) femur during extension  Aka. Medial rotation of femur WRT tibia  Closed kinetic chain o Medial (internal) rotation of femur WRT tibia during extension  Cause for phenomenon o Difference in femoral condyle sizes  Medial > lateral’s articulating surface  During extension, movement at the medial condyle continues after lateral condyle has stopped Summary  Knee flexion o Tibia medially rotates WRT femur o Posterior roll- contact migrates posterior  Menisci pushed posteiroly  Knee extension o Tibia laterally rotates WRT femur o Anterior roll- contact migrates anterior  Menisci pushed anteriorly 2/21/2013 2:00:00 PM Level walking- 3xBW Stair climbing- 4.25x BW Lifting- 2.12 x BW Jogging- 12.4 x BW Squatting- 7.6x BW Note: weight in closed kinetic chain = head/arms/trunk Weight in open kinetic chain= ankle Closed kinetic chain- lever arm  Moment arm of trunk weight increase with increasing knee flexion o More work done by quads to balance (knee extensors)  When standing: o COM located slightly anterior to knees creates small moment arm due to GRF that causes some extension at the knee  Knee hyperextension   This strategy is used for those with weak quads  When squatting o COM moves posterior to knee, GRF causes flexion moment arm that increases knee flexion angle. As squat increases, moment arm increases, force needed to counteract flexion produced by quads is increased (they need to work harder) Open kinetic chain  Moment arm (distance to axis of rotation- i.e. knee) of ankle weight and leg increases as knee STRIGHTENS thus increasing the flexion moment o More quads need to work to balance external force of ankle weight  As the knee flexes, the moment arm for the ankle weight will decrease, meaning the torque/moment produced is much smaller. This means the quads will not have to work as hard (i.e. contract) in order to counteract the external force What balances the ankle weight  Wuads create exteions to bal
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