Knee Joint Complex

Explain the patellofemoral Articulation

• Articulation between the patella and the patellar groove of the femur

  • Least congruent joint in the body

Explain Patellar Compressive force

As knee flexion proceeds, the pull of the quads and the pull of the patellar ligament become increasingly oblique, compressing the patella into the femur

What movement is there little to no compressive force on the patella

Full knee extension

Medial lateral forces on the patella are determined by line of action of?

• Quadriceps tendon

• Patellar ligament

The stability of the Tibiofemoral joint depends heavily on what restraints

Dynamic and static soft tissue restraints

What are the dynamic restraints

Quadriceps, Hamstrings and gastrocnemius

What are the static restrains

joint capsule, menisci, and ligaments

What are the functions of the menisci

• Increase contact surface area

• Distribute weight bearing

• shock absorption/ reduce stress

• Reduce friction

What is collateral ligament? What are they in the knee joint?

• Cross the medial and lateral aspects of the knee

  • MCL, LCL

What is cruciate ligaments?

Cross each other in connecting the anterior and posterior aspects of the knee

The MCL Runs from?

medial aspect of the femoral condyle to medial aspect of the proximal tibia

The LCL runs from?

Lateral femoral condyle to the head of fibula

The MCL primarily resits

Valgus

The LCL primarily resists

Varus

Genu Varum is known for

bow legged

Genu Valgum is known for

Knee knocked

Is varus positioning abduction or adduction

adduction

Is valgus positioning abduction or adduction

Abduction

What is the Q angle

Angle between two intersecting lines

What does line 1 represent in the Q angle

Center of the patella to the anterior superior iliac spine

What does line 2 represent in the Q angle

Patella to the tibial tuberosity

What is considered an abnormal Q angle

20 degrees or more

What is the course the ACL runs

Anterior tibia passing under transverse ligament to insert on inner posterior aspect of the lateral condyle of the femur

The Anterior Medial Bundle is taut in

Flexion

The posterolateral bundle is taut in

extension and often injured in hyperextension

What is the function of the ACL

Primary restraint for anterior translation of the tibia

What is the course the PCL runs

Posterior tibia to inner aspect of medial femoral condyle running somewhat anteriorly to attach on the lateral aspect of the medial femoral condyle

What is the function of the PCL

Primary restraint to posterior displacement of tibia.

Also helps resist varus and valgus stresses

Where does the oblique popliteal ligament run

posterior to the tibial medial condyle to central part of the posterior aspect of the joint capsule

What the Oblique popliteal ligament primarily resists

hyperextension + valgus

Where does the Arcuate ligament run

fibula head to intercondylar area of the tibia and to the lateral epicondyle of the femur

What does the arcuate ligament primarily resist

Varus stress + hyperextension

What are the 2 main DOF’s for the knee

• Flexion/Extension

• Medial/Lateral Rotation

In knee flexion what are the primary muscles

• Semimembranosus

• Semitendinosus

• Biceps Femoris

In knee flexion what are the secondary muscles

• Sartorius

• Gracilis

• Popliteus

• Gastrocnemius

What muscle plays a dynamic stabilizer role for the knee

Gastrocnemius

What muscles help stabilize the medial aspect of the knee joint

Sartorius, semitendinosus, gracilis via the pes anserinus

If a person lacks dorsiflexion ROM how will this affect Knee ROM during a squat? Why?

In Closed chain, a limitation at one joint will influence ROM at another

Lack of dorsiflexion will limit knee flexion

Define genu recurvatum

pathologic hyperextension of the knee especially seen during gait which of repeated loading can damage the posterior capsular ligaments

What are the primary muscles used for extension

• Vastus lateralis

• Vastus medialis

• Vastus intermedius

• Rectus femoris

What causes the femur to roll uphill as the knee flexes

The menisci

What causes the femur to slide down the hill

Shear forces

Explain Screw home mechanism

• Referred to as locking of the knee

  • Caused mainly by asymmetry in medial and lateral femoral condyles

Explain Initial flexion

“unlocking’ the knee

• Assisted via activation of the popliteus muscle

  • Unlocking will still occur in passive flexion

In closed chain movement how is flexion initiated

the medially rotated femur must laterally rotate

In open chain how is flexion initiated

the laterally rotated tibia must medially rotate

Explain Axial knee rotation

• Accessible only in knee flexion

• Distinct from screw as it accessible but not obligatory

• Due to joint laxity and incongruence

What is the primary muscle for lateral rotation

Biceps femoris

What are the primary muscles for medial rotation

• Semimembranosus

• Semitendinosus

• Sartorius

• Gracilis

• Popliteus

Explain Dynamic knee stability when preformin abduction/adduction

• ROM 8 degrees

• Resisting knee valgus stress muscles of the pes anserinus flexion

• Resisting knee varus stress

What are responsible for resisting knee varus stress

• iliotibial tract

• Biceps tendon

• Popliteus tendon

In anterior posterior movement what muscle prevents anterior translation of the tibia

hamstrings

In anterior posterior movement what prevents posterior translation of the tibia

• Popliteus

• Patella/Quadriceps