The Knee Flashcards
Joints at the knee
Tibiofemoral, patellofemoral, proximal tibiofibular
Menisci Function
Shock absorption, joint congruency, lubricating articular cartilage, guide knee’s osteokinematics, reduce friction
Medial Collateral Ligament (MCL)
Checks valgus forces (abduction)
Lateral Collateral Ligament (LCL)
Checks varus forces (adduction)
Knee Ligaments flexion vs extension
Ligaments slack in flexion and are pulled tight in extension
Anterior Cruciate Ligament (ACL)
Checks anterior displacement of tibia on femur
Posterior Cruciate Ligament (PCL)
Checks posterior displacement of tibia on femur
ACL Mechanism of Injury
Strong quadriceps activation with valgus collapse and excessive external rotation of knee; noncontact valgus load; knee hyperextension
PCL Mechanism of Injury
Falling onto a fully flexed knee; dashboard injury; hyperextension causing a gapping of posterior side of the knee
Tibiofemoral joint movements
2 degrees of freedom
flexion/extension in saggital plane
internal/external rotation in horizontal plane
Screw Home Mechanism Factors
- Shape of medial femoral condyle
- Tension in ACL
- Lateral pull of quads
Screw Home Mechanism Extension (Femur Fixed)
Tibia externally rotates on a fixed femur
Screw Home Mechanism Flexion (Femur Fixed)
Tibia internally rotates on a fixed femur
Screw Home Mechanism Extension (Tibia Fixed)
Femur internally rotates on fixed tibia
Screw Home Mechanism Flexion (Tibia Fixed)
Femur externally rotates on fixed tibia
Patella Function
Decreases friction on quadriceps tendon
Increases strength of quadriceps (increases moment arm and lengthens quadriceps muscle)
Patellofemoral Joint Forces
Quadriceps tendon and patellar ligament pull patella against femur
Patellofemoral Joint Forces Increase When…
Increased quadriceps force
Increased knee flexion angle
Max contact area at 30-90 of knee flexion
Q Angle
Indication of direction of pull of quadriceps muscle on the patella;
Angle between the line through the center of patella and tibial tuberosit and through center of patella and ASIS
Usually about 10-20 degrees
Increased Q Angle May Result in…
Excessive force on lateral patella
Lateral dislocation of patella
Anterior Knee Pain
Knee Extensors
Quadriceps….
Rectus Femoris
Vastus Lateralis
Vastus Intermedius
Vastus Medialis
Role of Vastus Medialis
Knee Extensor
Opposes lateral pull of vastus lateralis; Helps prevent lateral dislocation or lateral tracking of patella
Knee Flexors
Hamstrings (Semimembranosus, Semitendionsus, Biceps Femoris);
Ankle Plantarflexors (Gastrocnemius);
Popliteus
Pes Anserine
- Common Attachment of Sartorious, Gracilis, Semitendinosus
- Reinforces medial joint
- Attaches to medial meniscus
