Movement Science - The Knee

Tibiofemoral Joint

the point where the tibia meets with the femur

Patellofemoral Joint

the point where the kneecap and femur are connected in the trochlear groove

Tibiofemoral Alignment

- longitudinal axes normally form an angle medially of 180 to 185 degrees

Genu Valgus

- knock knees

- greater than 185 degrees

Genu Varus

- bow legs

- medial tibiofemoral less than 175 degrees

Which part of knee is most commonly arthritic?

- medial

Dynamic Valgus

- condition happens when person is moving "dynamic"

- happens during functional activities

Where does Dynamic Valgus come from?

- weak glute med (prevents adduction in closed chain)

- the foot (arch)

- tight adductors

- MCL could be torn

- weak glute max

Arthrokinematics - Knee Flexion and Closed Chain

- primarily, rolling occurs (posteriorly) the first 15-25 degrees

- anterior glide then accompanies the rolling

Joint Movements in Rotation

Meniscus

- weight bearing function

- reduce joint friction

- shock absorption

- lubrication

- both attach to tibial condyles

- attach to each other at anterior horns

Medial Meniscus

- C shaped

- open toward eminence

- firmly attached

- peripheral (outer bands) vascularization

- attaches to MCL, semimembranosus & patella

Lateral Meniscus

- O shaped

- Loose

- Posterior meniscofemoral fibers

- Attaches to PCL & popliteus

Menisci

- spread out forces across joint

Menisci Move with Femur

Cruciates

ACL, PCL

Collaterals

MCL, LCL

ACL

- commonly injured

- resists anterior translation of tibia

- resists hyperextension of the knee

- injury occurs most often when knee is slightly flexed and tibia is rotated either direction in Wb'ing

- assists w/ pulling femur anterior during closed chain flexion

Hamstring to Quadricep Relationship

- quads should be stronger than hamstrings

- ratio is 50-80% percent (hamstring:quad)

- elevated activity of vastus lateralis has increased risk

How does increased ham/quad ratio affect the knee?

- protective against ACL tears

- prevents tibia from moving anteriorly on femur

ACL Injury Risk

- knee valgus has been shown to be a significant predictor of ACL injury

- drop vertical jump is higher risk of valgus

- female are at higher risk

Landing Mechanics

- A) hip experiences more torque while landing

-B) more torque at knee, less torque at hip

Landing Mechanics PT.2

- A) Uses more glute max, glute min. Recovering from knee injury

- B) recovering from labral tear. Uses less hip and more knee

Knee/Hip Moment Ratio

- torque in female patients are higher than males

PCL

- resists posterior shear (displacement) of knee

- cross-sectional area 120%-150% that of ACL

- PCL restricts hyperflexion

MCL

- restricts valgus stress

- becomes more lax with flexion

- has capacity to heal because if its rich blood supply

LCL

- resists varus stress

- also resists lateral rotation

- MCL is twice as strong as LCL

- only 2% of knee injuries are LCL

Tibia internally rotates

- stress acl and mcl

Tibia laterally rotates

- stresses mcl

Patellofemoral Joint Function

- anatomic pulley for the quad

- 3rd class level

- joint congruency (surface area of bone on bone contact) and compression is minimal in extension

- increases with flexion of knee

With flexion, the patella moves ________?

- distally

With extension, the patella moves _______?

- superiorly

Patellofemoral Kinematics

- area of contact moves proximally as the patella moves into flexion

- alters patellofemoral joint stress

Patellofemoral Syndrome

- pain at the patella joint

Patella Baja

low riding patella

Patella Alta

high riding patella

Mechanical Advantage

1) increase moment arm

2) changes direction of force

3) decreases friction on anterior joint

Patellofemoral Joint Reaction Force

- influenced by quad force and knee angle

- increases with the knee in a flexed position. decreases with extension position

- during normal walking, PF compressive force is 25-50%

- running can increase this to 5-6 times body weight