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United States (324,289)
PT 5131 (30)
L Day (25)
Lecture

Knee Joint.docx

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Department
Physical Therapy
Course
PT 5131
Professor
L Day
Semester
Spring

Description
Knee Joint (General) Angles • Due to angle of inclination of femur, the femur slants medially • Q-Angle: in between a line drawn from ASIS to Central Patella and the Vertical Axis o About 13°-15°, with females Q-Angle > male Q-Angle o Important because helps describe pull of quadriceps tendon  Also causes patella to track laterally o Can be increased by:  Genu valgum  Increased femoral anteversion  External tibial torsion  Tight lateral retinaculum  Laterally positioned tibial tuberosity • Angle Between Femur and Tibial Shafts o Estimated using Q-Angle, or measured using goniometer o Roughly 170°-175° o Genu Valgum: < 170°  “Knock Knees”  Like having tibia abducted, with respect to Femur  Knees in, ankles out o Genu Varum: > 180°  “Bow Legged”  Knees out, ankles in Knee Joint • Modified hinge joint (bicondyloid joint) o Combines both rolling and gliding • 6 Degrees of Freedom: o Main: Flexion/Extension, Internal/External Rotation (only occur when knee is flexed) o Minimal amount of Anterior/Posterior gliding and Medial/Lateral gliding  Dependent upon laxity of ligaments, capsule, and muscles o When knee is under stress we can distract (pull apart) or compress (push together) the knee joint o Varus Stress/Force: bend inward  Varus force is when the distal end of a bone or joint moves medial in relation to the proximal end of a bone or joint.  Pressure applied at medial aspect of knee  Cause tear in LCL o Valgus Stress/Force: bend outward  Valgus force is when the distal end of a bone or joint moves lateral in relation to the proximal end of a bone or joint.  Pressure applied at lateral aspect of knee  Cause tear in MCL • Knee joint is 3 articulations in one o 2 femorotibial o 1 femoropatellar o Fibula is not involved  Only acts as splint for tibia and site for muscle attachment • Knee is inherently unstable, due to articular surfaces o Gain stability through muscles and ligaments Anterior Knee • Patella, Quadriceps tendon, patellar ligament (patellar tendon) o Combination of tendons explain why contraction of quadriceps move the patella and tibia, thus extending our knee joint • 2 Retinaculums (extension of fascia from quadriceps tendon) o Lateral Retinaculum: thicker than medial retinaculum o Medial Retinaculum: o Help stabilize patella and make sure it tracks appropriately during knee flexion and extension Joint Capsule • Typical joint capsule with an external fibrous layer and an internal synovial membrane • Thin and incomplete in 2 major areas: o Opening for Popliteus in back o In front where Quadriceps and Patella replace capsule (no anterior capsule) • Attaches just superior to articular margin of femoral condyles margin of tibial plateau • Reinforced by muscles and connective tissue: Region of Connective Tissue Muscle/Tendon Reinforcement Capsule Reinforcement Anterior • Patellar Ligament Quadriceps • Patellar Retinacular Fibers Lateral • Lateral Collateral Ligament • Biceps Femoris (LCL) • Tendon of Popliteus • Lateral Patellar Retinacular • Lateral Head of Gastrocnemius • Iliotibial Tract Posterior • Oblique Popliteal Ligament • Popliteus • Arcuate Popliteal Ligament • Gastrocnemius • Hamstrings Medial • Medial Cruciate Ligament • Expansions from (MCL) Semimembranosus • Medial Patellar Retinacular • Tendon of Sartorius • Tendon of Gracilis • Tendon of Semitendinosus Synovial Membrane of the Knee • Lines articular capsule of knee • Synovial membrane does not surround ACL and PCL o Infrapatellar Synovial Fold: apparently 2 cavities • Continuous with Suprapatellar Bursa, which comes up and above knee o Genu Articularis: located above Suprapatellar Bursa  Proximal Attachment: anterior shaft of Femur  Distal Attachment: Suprapatellar bursa  Nerve Innervation: Femoral Nerve (L2 – L4) • Innervated at same time quadriceps are innervated o When quadriceps contract to extend knee, genu articularis contracts and pulls suprapatellar bursa up and in place  Action: holds Suprapatellar bursa in place Bursa • Roughly 14 bursa located in knee • 4 bursae communicate with/are and extension of synovial cavity o Suprapatellar Bursa: located between quadriceps tendon and femur o Pes Anserine Bursa: located between 3 muscles attached to Pes Anserine and Tibia o Popliteus Bursa: located between popliteus tendon and tibia and fibula o Gastrocnemius Bursa: separates gastrocnemius from femoral condyles • Subcutaneous/Subtendinous Prepatellar Bursa: located between skin and patella • Subcutaneous/Deep Infrapatellar Bursa: sit on either side of patellar ligament, as it attaches on to tibial tuberosity Fat Pads • Suprapatellar Fat Pad: sits above patella, deep to quadriceps tendon • Infrapatellar Fat Pad: sits between patellar ligament/tendon and tibial tuberosity o AKA “Hoffa’s Pad” o Can actually get impinged between femoral condyles and patella during flexion/extension  Causes severe pain Knee Join (Plicae and Menisci) Patellar Plicae • Commonly occurring synovial folds occurring within joint lining of knee • Embryologic remnants that failed to absorb after fetal development • Generally asymptomatic and serve no physiological purpose o Can become irritated and cause symptoms • 4 Types: o Suprapatellar o Infrapatellar o Mediopatellar o Lateral Patellar Suprapatellar Plica • Found at border between suprapatellar bursa and knee joint cavity • Runs obliquely and in downward fashion from synovium to posterior aspect of quadriceps tendon o Inserting immediately superior to patella • Origin and Insertion o Underneath quadriceps tendon o Oblique downward orientation o Attaches just above patella • Variations: o Size o Complete Septum: divides suprapatellar pouch from rest of knee  Less common, but most problematic o Complete Septum with “Porta”: centrally placed hole in complete septum o Crescent-Shaped Fold: originating medial and posterior to quadriceps tendon, just above tendon  Most common suprapatellar pica Infrapatellar Plica • AKA Ligamentum Mucosum • Most prevalent type of plica • Not commonly symptomatic o Easily not diagnosed • Origin and Insertion o Origin: intercondylar notch of femur o Insertion: apex (bottom) of patella o Fibers run horizontal  Appears to be running with anterior cruciate ligament • Variations o Isolated Cord: no attachment to ACL o Web-Like: fibers attach to ACL near its insertion on patella o Septum: divides knee joint into medial and lateral compartments • Can be mistaken for ACL commonly Mediopatellar Plica • Thin, elastic, and well vascularized o Allows for reconfiguration and manipulation as knee flexes and extends • Size and shape vary greatly o Small ridge o Shelf o Well form cord • Origins and Insertions o Origin: posterior to medial retinaculum, attached to genu articularis muscle o Travels parallel to medial border of patella o Insertion: infrapatellar fat pad • 4 types: o Type A and B: smaller and generally clinically insignificant o Type C and D: larger and may become trapped between medial femoral condyles and patella, especially during repetitive flexion and extension activities • Observed less frequently than suprapatellar or infrapatellar plica o BUT, majority of symptomatic clinical findings are Mediopatellar Plica Lateral Plica • Least common type of patellar plica • Commonly asymptomatic • Origins and Insertions
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