Knee Joint actually 2 joints within the articular capsule tibio-femoral patello-femoral the superior fibulo-tibial joint is also near modified hinge joint flexion and extension is primary motion some rotation is possible when the knee is flexed Knee

Anterior Posterior Transverse condyles epicondyles intercondylar notch patella tibial tuberosity tibial plateaus

Ligamentous Support Menisci Cruciate Ligaments Other Collateral

Menisci The menisci are discs of fibrocartilage attached to tibial plateaus. They are thicker along the periphery.

The lateral meniscus is smaller and more mobile than the medial meniscus. The inner portion of the menisci are avascular. The outer portion has some blood supply, making healing of tears possible. lateral medial

Menisci Function increases stability by deepening tibial plateaus decreases friction by 20% increases contact area by 70% absorbs shock removal of menisci does NOT preclude normal motion, but increase wear on articulating surfaces increase chance of developing degenerative joint disease

Collateral Ligaments lateral (fibular) medial (tibial)

Collateral Ligaments prevents abduction and adduction movement of the knee Collateral Ligaments

Additional Ligamentous Support iliotibial band thick, strong band of tissue connecting tensor fascia latae to femur and tibia

Cruciate Ligaments cruciate -- ‘cross’ ligaments form an ‘X’ or cross within the joint named for their TIBIAL attachments Anterior Cruciate (ACL)

Posterior Crucuate (PCL) shorter and stronger than ACL

The ACL prevents the femur from sliding posteriorly on the tibia or the tibia from sliding anteriorly on the femur. FEMUR The PCL prevents the femur from sliding anteriorly on the tibia or the tibia from sliding posteriorly on the femur. PATELLA TIBIA

The PCL prevents the tibia from sliding posteriorly on the femur. Anterior Posterior

Cruciates During Flexion/Extension Note: the cruciate ligaments also limit rotation

Patello-femoral Joint articulation of the patella and femur the patella is a true sesamoid bone posterior surface of the patella is covered with thick hyaline cartilage the patella slides within the trochlear groove

Functions of Patello-femoral Joint with patella without patella (1) increases angle of pull of quads on tibia, improves the ratio of motive:resistive torque by 50% (2) centralizes divergent tension of quads into a single line of action (3) some protection of anterior aspect of knee

Q-Angle The Q-angle is the angle formed by a line from the anterior superior spine of the ilium to the middle of the patella and a line from the middle of the patella to the tibial tuberosity. Males typically have Q-angles between 10 to 14o, females between 15-17o.

Atypical Q-angles bowleggedness knock-knees

Knee Rotation (Locking Your Knee) Flexion External Rotation Internal Extension Knee Rotation (Locking Your Knee) Six to 30 degrees of internal rotation of the tibia on the femur occurs through 90 degrees of knee flexion. The femoral condyles do not have the same diameters, this helps cause internal rotation when the knee is flexed and external rotation when the knee is extended. The lateral condyle slides more than medial condyle. The anterior cruciate ligament becomes taut just prior to the rotation, this may help force a rotation of the femur on the tibia.

Knee Musculature many 2 joint muscles primary movements - flexion and extension - hams & quads, respectively medial and lateral rotation possible necessary for screw- home mechanism

Knee Flexion Hamstrings cross hip and knee biceps femoris semitendinosus semimembranosus gastrocnemius cross knee and ankle popliteus

Knee Extension - Quadriceps rectus femoris vastus lateralis vastus medialis vastus intermedius quadriceps tendon patellar ligament

Lateral Rotation biceps femoris attaches to lateral aspect of knee

Medial Rotation semitendinosus semimembranosus popliteus attach to medial aspect of knee

Common Knee Injuries one of the most commonly injured joints lack of bony and muscular support positioned between the 2 longest bones weight bearing and locomotion functions often tear or stretching of soft tissue

Ligament Injuries ACL PCL more prevalent than PCL injuries forces directed from posterior side of leg PCL forces directed from anterior side of leg forced flexion of knee w/external rotation wrestling and football

Ruptured ACL Knee Intact Knee with ACL & PCL

Mechanisms of ACL injury 1) attempting a rapid cutting maneuver with foot in contact with the ground and knee flexed (problem exacerbated if an external force applied to knee during this movement) 2) knee hyperextension with internal tibial rotation Example backward falling skier - boot and skis accelerate forward creating an anterior drawer mechanism

Gender issues related to ACL injuries females more likely to sustain an ACL injury than males soccer - 2.6X basketball - 5.75X wider pelvis greater flexibility less-developed musculature hypoplastic vastus medialis obliquus narrow femoral notch genu valgum external tibial torsion

PCL Injuries When the knee is forcefully twisted or hyperextended BUT other ligaments are usually injured or torn, before the posterior cruciate ligament (PCL) is torn Most common mechanism for PCL alone to be injured is from a direct blow to the front of the knee while the knee is bent.  Automobile accident Automobile strikes another and stops suddenly Front passenger or driver slides forward.  Bent knee hits the dashboard just below the knee cap forcing tibia backwards on the femur tearing PCL. The same force can occur during a fall on the bent knee, where the force of the fall on the tibia pushes it back against the femur and tears the posterior cruciate ligament (PCL).

Common mechanism of PCL injury in football is being tackled while the knee is fully extended. When the tibia is displaced too much in the posterior direction the PCL may rupture.

Ligament Injuries injuries to MCL more prevalent than LCL MCL foot planted and force applied to the lateral side of knee football

Meniscus Injuries most common injury in the knee tearing is most common medial side injured more often medial meniscus more secured foot planted with excessive rotation

Iliotibial Band Syndrome IT-band thick strong band of ligamentous tissue connects tensor fascia latae to the lateral condyle of the femur and the lateral tuberosity of the tibia IT-band rubs against the lateral femoral condyle when there is excessive tension

excessive pronation increases internal rotation of the tibia, which accentuates the friction of the IT band and femoral condyle tibial alignment and size of femoral condyle may also contribute to the development of this condition