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