Knee Jointactually 2 joints within the articular capsuletibio-femoralpatello-femoralthe superior fibulo-tibial joint is also near

modified hinge jointflexion and extension is primary motionsome rotation is possible when the knee is flexed

Ligamentous SupportMenisciCollateralLigamentsCruciateLigamentsOther Ligaments

MenisciThe 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.lateralmedial

Menisci Functionincreases stability by deepening tibial plateausdecreases friction by 20%increases contact area by 70%absorbs shockremoval of menisci does NOT preclude normal motion, butincrease wear on articulating surfaces increase chance of developing degenerative joint disease

lateral (fibular)

medial (tibial)Collateral Ligaments

prevents abduction andadduction movementof the kneeCollateral Ligaments

Additional Ligamentous Supportiliotibial bandthick, strong band of tissue connecting tensor fascia latae to femur and tibia

Anterior Cruciate (ACL)

Cruciate Ligaments

cruciate -- cross ligaments form an X or cross within the joint

named for their TIBIALattachments

Posterior Crucuate (PCL)

shorter and stronger thanACL

FEMURTIBIAPATELLA

The PCL prevents the tibia from sliding posteriorly on the femur.AnteriorPosterior

Cruciates During Flexion/ExtensionNote: the cruciate ligaments also limit rotation

Patello-femoral Joint articulation of the patella and femurthe patella is a true sesamoid boneposterior surface of the patella is covered with thick hyaline cartilagethe patella slides within the trochlear groove

Functions of Patello-femoral Joint(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 kneewithout patellawith patella

Q-AngleThe 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-anglesbowleggednessknock-knees

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 Musculaturemany 2 joint muscles

primary movements - flexion and extension - hams & quads, respectively

medial and lateral rotation possible necessary for screw- home mechanism

Knee FlexionHamstrings cross hip and knee

biceps femoris

semitendinosus

semimembranosus

gastrocnemius cross knee and anklepopliteus

rectus femoris

vastus lateralis

vastus medialis

vastus intermedius

quadriceps tendon

patellar ligament

Knee Extension - Quadriceps

Lateral Rotationbiceps femoris attaches to lateral aspect of knee

Medial Rotation

semitendinosus

semimembranosuspopliteusattach to medial aspect of knee

Common Knee Injuriesone of the most commonly injured jointslack of bony and muscular supportpositioned between the 2 longest bonesweight bearing and locomotion functionsoften tear or stretching of soft tissue

Ligament InjuriesACLmore prevalent than PCL injuriesforces directed from posterior side of legPCLforces directed from anterior side of legforced flexion of knee w/external rotationwrestling and football

Intact Knee with ACL& PCLRuptured ACL Knee

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

Examplebackward 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 malessoccer - 2.6Xbasketball - 5.75X

wider pelvisgreater flexibilityless-developed musculaturehypoplastic vastus medialis obliquusnarrow femoral notchgenu valgumexternal 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 accidentAutomobile strikes another and stops suddenlyFront 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).

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

Ligament Injuriesinjuries to MCL more prevalent than LCLMCLfoot planted and force applied to the lateral side of kneefootball

Meniscus Injuriesmost common injury in the kneetearing is most commonmedial side injured more oftenmedial meniscus more securedfoot planted with excessive rotation

Iliotibial Band SyndromeIT-bandthick strong band of ligamentous tissueconnects tensor fascia latae to the lateral condyle of the femur and the lateral tuberosity of the tibiaIT-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

Knee