KIN 3304 Chapter 9: The Knee Joint
Q Angle
-Central line of pull for entire quadriceps -Line of pull of patella tendon -Angle formed by the intersection of these two lines at the patella is the Q angle -Wider pelvis (hip) increases Q angle
Bones of knee joint
-Femur -Patella (knee cap) ~sesamoid -Tibia ~weight bearing -Fibula ~non-weight bearing
Injuries to the Knee (Patellofemoral Syndrome)
Patellofemoral Syndrome -Pain in and around the patellofemoral joint -More common in females --Potential cause is a greater Q angle ---In men, angle tends to be 10-15 degrees ---In women, angle tends to be 15-20 degrees ---A Q angle of 20 degrees or more will put extra stress on the patellofemoral joint
When knee extended (straight leg)
-knee stabilized from its vertical alignment and the fit of the joint surfaces
Knee Joints (Collateral Ligaments & Cruciate Ligaments)
Collateral Ligaments: -Medial Collateral Ligaments -Lateral Collateral Ligaments --Side to side stability Cruciate Ligaments: -Anterior Cruciate Ligaments -Posterior Cruciate Ligaments --Front to back stability
Knee Muscles (anterior)
Mostly knee extension *Rectus femoris -Vastus intermedius -Vastus lateralis -Vastus medialis *Gracilis
Knee Muscles (posterior)
Mostly knee flexion ^Biceps femoris ^Semimembranosus ^Semitendinosus *Sartorius (anterior muscle) -Popliteus -Gastrocnemius -Plantaris
Gastrocnemius Muscle (calf muscle)
-Action: (knee: flexion) -Application: (propel body upward and forward) (running, jumping, skipping)
Hamstrings (hip extensors and knee flexors)
-Biceps femoris -Semimembranosus -Semitendinosus *Named for cord-like attachment at knee *Posterior muscle group, antagonists to quadriceps --Hip extension, internal and external rotation --Knee flexion, internal and external rotation
Iliotibial Band (IT)
-Combination of gluteus maximus and tensor fasciae latae tendons of insertion -Crosses the knee near lateral condyle of femur and inserts on to anterior portion of lateral tibial condyle -Assists with flexion and extension of the knee --Between full extension and 10-15 degrees of flexion, located anteriorly to lateral femoral condyle and assists with extension --Past 15 degrees of flexion, shifts to posterior to lateral femoral condyle and assists with flexion
Obligatory Terminal Rotation (screw home movement)
-During last 30 degrees of knee extension on fixed femur, the tibia externally rotates about 10 degrees -The tibiofemoral joint 'locks' into place in full extension -Results from: --Condylar structure --Ligament tension ---ACL, medial and lateral collateral ligaments Factor's Guiding "screw home" Rotation -shape of medial femoral condyle -tension in anterior cruciate ligament -lateral pull of quadriceps
Injuries to the Knee (Anterior Cruciate Ligament Sprain)
-Femur and tibia twisting in opposite directions under full body weight stresses ACL -Ankle braces and certain footwear may transfer stress to the knee -Imbalances in quadriceps-hamstrings strength ratio -Females tend to injure ACL more often than males --Potential Causes: ---Having proper muscle balance supports the knee ---Hamstring 60-80% as strong as quadriceps
Knee Joints (tibiofemoral articulation)
-Femur articulates with the tibia and with the patella -Tibiofemoral articulation (knee joint) ~Modified hinge joint --Flexion and Extension --Internal and External rotation during flexion ~Static stability-ligaments ~Dynamic stability- hamstrings/quadriceps muscle groups --hamstring: flexors --quads: extensors -Ligaments hold the knee together -Dynamic stability comes from musculature
Femur Movement
-Femur rolls and glides over both menisci during extension-flexion
Popliteus Muscle (posterior)
-Flexion and Internal Rotation -Only pure knee flexor -Unlocks knee from "screwed home" full extension position
Patellofemoral Joint Movement
-Gliding motion
The Knee
-Largest diarthrodial joint in the body, is very complex -The knee joint supports the weight of the body above it, and transmits forces to the ground below, as well as allows movement between the femur and tibia -This combination of weight-bearing and locomotion place stress on the joint
Femur of Knee
-Lateral and medial femoral condyles ~Articulation with tibia, patella ~Medial condyle is slightly more distal and slightly larger than lateral *femur projects obliquely/ at a slant*
Tibia of Knee
-Lateral and medial tibial condyles ~Articulation with femur -Gerdy's tubercle ~Insertion of IT band -Tibial tuberosity
Two-joint Muscles (biarticular)
-Muscles are able to exert greater force when lengthened than when shortened -Hamstring muscles, rectus femoris, sartorius, and gracillis have action at hip and knee Ex: Sartorius- total length increases when the pelvis is rotated posteriorly and it becomes more effective at flexing the knee Ex: Rectus Femoris- A football kicker leans backward to raise and fix the origin of the rectus femoris muscle
Knee Joints (patellofemoral articulation)
-Plane joint -Function: (mechanical advantage) (increases angle of pull)
Quadriceps Group
-Rectus femoris (originates from pelvis) -Vastus intermedius (originates from femur) -Vastus lateralis (originates from femur) -Vastus medialis (originates from femur) Attach to patella and insert at tibial tuberosity Anterior muscle group responsible for knee extension
Tibiofemoral Joint Movement
-Sagittal Plane --Maximal extension: 5-10 degrees --Maximal flexion: 120-150 degrees -Transverse Plane --With knee flexed 30 degrees or more: ---Internal rotation of 30 degrees ---External rotation of 45 degrees
Knee Joints (Menisci)
-Semilunar fibrocartilaginous structures within the joint cavity of the knee -Each knee has menisci on proximal end of tibia, on the medial and lateral condylar surfaces -Cushion, enhance stability --Deepen receptacle for femoral condyle -Each knee has 2 menisci --Lateral and Medial
Plantaris Muscle
-Short belly with long tendon of insertion -Origin: linea aspera and oblique popliteal ligament -Insertion: calcaneus (heel) -Action: assists with flexion --Will have some action at the ankle
Injuries to the Knee (Medial or Lateral Collateral Ligament Sprain)
-These ligaments stabilize the knee joint and prevent abduction and adduction -Lateral force stress MCL Medial force stress LCL
Knee Extensors
-Vastus Lateralis -Vastus Intermedius -Vastus medialis
Injuries to the Knee (Torn Meniscus)
-Very common in sports, particularly the medial meniscus --Excessive rotation to femur on flexed tibia --Stress to medial collateral ligament could disrupt the meniscus -Results in popping noise, locking knee, eventual pain and swelling -Different tears have different treatments --If outer portion tears, may heal on own; inner tears need surgery
Hamstring Muscles
-biceps femoris: lateral and rotates externally (2 heads) -semitendinosus: medial and rotates internally -semimembranosus: medial and rotates internally *tibia: medial ; fibula: lateral*
When knee flexed (bent leg)
-the knee stabilized by capsule, ligaments, and muscles
