Kinesiology: Knee

Which meniscus tears will cause bunching of the meniscus and locking of the knee joint?

Posterior tear of horn's attachment

-can get bunching anteriorly and locking sometimes as a person walks

-doesn't allow for free movement of going through the whole knee ROM while walking

-can become a candidate for meniscectomy

Tear halfway to the collateral ligament

-medial part of meniscus bunches toward/inside knee joint

-may need meniscectomy

What may happen when you go into knee flexion and extreme unnatural valgus position ie) football player is hit sideways while bending? What is this called?

Valgus theory of meniscus tear

The medial meniscus may shoot into the medial part of the knee joint

And then when you go to extend and come back up to a normal position part of that meniscus gets stuck in there and it gets torn

Name the 3 members of the unhappy triad

ACL, MCL and medial meniscus injured at the same time

Severe ligamentous strain

End up with very unstable knee joint

Describe the knee joint.

double condyloid joint

2 degrees of freedom: flex/ext (sagittal plane), rotation (transverse plane)

articular surfaces: femoral & tibial articular surfaces

T/F A tear in the posterior 3rd of the meniscus will lead to bunching of the meniscus and locking of the knee joint

F

This tear is not such a big deal, the whole thing will just come back together

Meniscus will spring back into its normal position

No long term problems

No meniscectomy required

T/F You will need a meniscectomy for a complete/bucket tear because it is a much more extensive tear than the others

F

Even though this is a much more extensive tear than the others, won't need a meniscectomy because there is no

bunching and locking which gets in the way of functioning

Central portion of the meniscus may move into the center of the joint

What is patella alta?

high riding patella

excessively long patella tendon compared to patella length; not the 1:1 ratio that is usual

Will have abnormally high position of the patella sitting on femoral sulcus

The patella will have little or no contact with the femoral sulcus

T/F the patella is pulled slightly medially

F

The patella tends to be pulled slightly laterally

What happens to knee extension after a patellectomy? How is walking/standing affected after a patellectomy?

After patellectomy, you will not be able to get full extension of the knee joint when sitting and trying to extend knee

• Open chain kinematics trying to extend the knee is problematic because the moment arm is too small for the quads to generate sufficient torque after a patellectomy

However, a patellectomy doesn't interfere with our ability to come into standing. You can still weight bear on the leg and the leg won't buckle and cause you to fall. There is no problem with sitting to standing and standing to walking. Closed chain kinematics is not problematic post patellectomy (you don't use quad muscles much while walking/standing).

What is the pes anserinus?

Goose's foot

Insertion of sartorius, semitendinosus and gracilis (anteromedial aspect of proximal tibia) where bursa may cause knee pain (pes anserinus bursitis)

Six - sartorius

Silly -semitendinosus

Geese- gracilis

important stabilizer to the medial aspect of the knee joint

What is the Q angle?

Clinical assessment of the pull of the quads on the patella

The intersection of a line from the ASIS through the patella and from the tibial tubercle through the middle of the patella.

T/F Lateral femoral condyle and lateral tibial plateau are larger than the medial femoral condyle and medial tibial plateau respectively

False- medial femoral condyle and medial tibial plateau are larger

In full knee extension, what happens to the knee joint capsule, bursae and ligaments?

o Synovial fluid is shifted anteriorly

§ Everything back in the posterior side becomes taut and compressed and pushes the fluid anteriorly

o Posterior aspect of joint capsule becomes taut

o All the ligaments at the knee become taut

§ Except the PCL (taut when knee flexes)

o Gastrocnemius bursa and subpopliteal bursa become compressed

§ Because they are found on the posterior side

§ Get flattened out

How do you unlock your knee?

When your knee is fully extended, the knee is locked in knee extension and must get a rotation of the knee (unscrewing the knee) to "unlock" the knee to flex it

When knee is fully extended, there is some external rotation of the tibia on the femur, meaning the tibia tubercle is lateral to the patella of the knee = knee is locked in full extension

In order to unlock and flex the knee from full extension, the tibia needs to unlock and slightly internally rotate

Which generates more torque, isometric vs isokinetic contractions?

isometric

In full knee flexion, what happens to the knee joint capsule, bursae and ligaments?

o Synovial fluid is shifted posteriorly

§ Everything in the front becomes taut and compressed and pushes the fluid posteriorly

§ Fluid has to go to an area where there is not much compression

• Think of squeezing a fluid filled balloon

o Anterior aspect of joint capsule becomes taut

o PCL becomes taut

o Suprapatellar bursa becomes compressed

§ Because it is found on the anterior side

Why are quad muscles affected after a patellectomy?

The person will have a decreased moment arm for knee extension thus decreasing quad muscle efficiency.

Isokinetic vs isometric

isokinetic: moving through the ROM at the same speed/rate/amount of muscle force through entire ROM

isometric: The joint is not moving at all; muscles are contracting, there is muscle force being generated but there is no movement taking place

ex) using muscles to keep other muscles stable/in position

T/F There is good congruency between the femoral condyles and tibial plateaus

False

Incongruency is improved by menisci

Why does the locking of the knee/screw home mechanism occur during the last 30 degrees of knee extension?

The medial femoral condyle is longer than the lateral femoral condyle

So rotation occurs along with the rolling and gliding during the last 30 degrees of knee extension

T/F The faster you contract a muscle, the more force you can generate.

False

The slower you contract the muscle, the more force you can generate

The faster you contract, the less amount of torque you can generate

• Known as the force-velocity relationship (the velocity of the contraction)

Which flexor knee muscle reverses the direction of the automatic rotation (unlocks the knee) that occurs during the locking of the knee joint?

Popliteus

Also it is not a great flexor of the knee bc it's right over axis of rotation

What direction do the menisci move during knee flexion?

posteriorly

What direction do menisci move during knee extension?

anteriorly

T/F. The normal Q-angle of the knee is up to 25 degrees for men and 30 degrees for women when the knee is straight.

F

15 degrees in adult males, and slightly higher in females

What is the screw home mechanism?

AKA locking and unlocking mechanism of the knee

An accessory and automatic locking and unlocking mechanism that takes place at the knee during the last 30 degrees of full knee extension

When knee is fully extended, there is some external rotation of the tibia on the femur, meaning the tibia tubercle is lateral to the patella of the knee = knee is locked in full extension

When is the PCL taut?

taut in full knee flexion

the only ligament that becomes taut at full knee flexion (calf helps limit full knee flexion too)

What are the functions of the medial and lateral menisci?

o Helps with the delicate balance of mobility and stability that is needed at the knee joint

o Improves the articulation between the tibial plateaus and femoral condyles

o Through its ability to improve the congruency, it helps distribute the weight bearing forces much better

o Also helps to reduce friction between the two joint surfaces

Which meniscus is more commonly injured?

medial meniscus

Has a much firmer attachment to the surrounding structures

Less moveable than the lateral meniscus

What would be an abnormal q angle?

Greater than 20 degrees

• In both males and females

Individual who has an increased Q angle, also probably has genu valgum

Will also have excessive lateral forces

How is the isokinetic quads torque determined?

1) The distance of its moment arm

• The longer the moment arm, the more force you can generate • Biomechanical factor

2) The length of the quads muscle

• Physiological factor

3) The velocity of the contraction aka force-velocity relationship

• The slower you contract the muscle, the more force you can generate

Why are children less prone to meniscal tears than adults?

Children have better vascularization throughout the menisci than adults whose menisci are only vascularized at the periphery.

In closed chain kinematics, sitting down/flexing the knee follows which rule (concave/convex)?

Convex rule- femur (convex) moving on fixed tibia (concave)

Which direction will the femoral condyles roll and glide when you sit down(flex the knee in a closed chain)? How is gliding facilitated?

Femoral condyles will roll posteriorly, glide anteriorly when sitting down

Anterior glide is facilitated by ACL and by the wedge

shape of the menisci

T/F There is a natural physiological varus at the knee

False

There is a physiological valgus at the knee (normal)

The long axis of the femur is directed medially

o When going from top down to the distal end

Whereas the long axis of the tibia is directed almost vertically

o Straight up and down

What are the functions of the ACL?

Prevents:

• Hyperextension of the knee

• Anterior movement of the tibia on the femur

• Posterior movement of the femur on the tibia

What is the measurement in degrees of the natural valgus at the knee?

185-190 degrees

If you injure your LCL, which knee muscle will be especially important to strengthen to stabilize the knee joint?

Biceps femoris (knee flexor & laterally/externally rotates tibia)

Forms a stabilizing role at the posterolateral aspect of the knee joint and attached to the lateral joint capsule

Because a valgus exists at the knee naturally, is there unequal pressure/stress on the medial and lateral side of the knee?

No, there is the same amount of weightbearing stress on both the medial and lateral sides of the knee

When are the ACL and PCL both taut?

Both taut at extremes of internal and external tibial rotation

When you stand up (extend the knee in closed chain), what happens to the femoral condyles and menisci? How is movement facilitated?

Femoral condyles roll anteriorly and glide posteriorly, opposite of knee flexion in a closed chain

Posterior glide is facilitated by PCL and by the wedge

shape of menisci

Menisci distort anteriorly

What is genu valgum?

knock kneed

-The medial tibiofemoral angle is 195 degrees or greater

-Increased compressive forces laterally and increased tensile forces medially

How many degrees of knee flexion are needed for walking, stair climbing and sitting in a chair?

o Need 60 degrees of knee flexion for walking

§ In order to get good toe clearance - so you don't trip on your foot

o Need about 80 degrees of knee flexion for stair climbing

§ Depends on how high the stairs are

o Need 90 degrees of knee flexion for sitting in a chair

What is genu varum?

bow legged

-The medial tibiofemoral angle is 180 degrees or less

-Increased compressive forces medially and increased tensile forces

laterally

What is the function of the patella? How does it achieve its function?

Improves the muscle efficiency of the quadriceps muscle to extend the knee because it increases the moment arm for the extension at the knee joint

Also helps reduce friction btw the quads tendon and femoral condyle

What happens to the menisci during the locking-unlocking of the knee?

Menisci distorts due to tibial rotation on the femur and to help maintain the relationship between the femoral condyles and the tibial plateaus

Name the functions of the gastrocnemius

Dynamic stabilizer during walking

Flexes the knee

Prevents knee hyperextension during push off

Holds the ankle and allows the ankle to eccentrically dorsiflex slowly to help prevent the knee from collapsing. Or else the tibia would roll too far/fast over the fixed foot and the knee joint will buckle and you will fall

When is the ACL taut?

full knee extension

Which knee flexor muscles also medially rotate the tibia?

Semimembranosus, Semitendinosus, gracilis & popliteus

What structures help prevent knee hyperextension?

ACL

Posterior capsular ligaments : oblique popliteal, arcuate popliteal

How many cc's of air or fluid can be held in the knee joint capsule before causing tension?

30-40cc's

What are the functions of knee ligaments?

Controls:

1.Excessive Knee Extension (Genu recurvatum) - also controlled by posterior joint capsule

2.Varus/Valgus Stresses

3.Anterior/Posterior Tibial Displacement on femur

4.Medial/Lateral Tibial Rotation

5.Combination of Anterior/Posterior Displacement and Rotation of Tibia

When does the medial and lateral collateral ligament become taut and slack?

MCL and LCL becomes taut in full knee extension and slack in knee flexion

Which collateral ligament has attachments to soft tissue of the joint itself?

Medial Collateral Ligament (MCL)

The MCL resists what direction of force?

Valgus (lateral) originating force

Because it is found on the medial side of the knee so when you go into genu valgus, the medial collateral ligament will become taut

Why is the LCL injured less than MCL?

LCL has no attachments to the soft tissue of th joint and can get out of the way of forces

When you sit down (flex the knee in a closed chain), what happens to the menisci?

Menisci distort posteriorly

§ To help maintain congruency between joint surfaces

§ Menisci distorts in the direction to which the motion

is taking place

§ True for both closed and open chain

What does the lateral collateral ligament resist?

Resists from going in to genu varus

Because it is found on the lateral side of the knee, it will become taut if you go into a varus position of the knee

When can we generate the greatest amount of both isometric and isokinetic force at the knee?

At 120 degrees (complimentary to 60 degrees)

At 120 degrees, everything is aligned

The distance of the moment arm for the quads tendon is the greatest

The length of the quads muscle is at its most ideal

• The muscle isn't too stretched out, and its not too contracted

What is the instantaneous axis of rotation?

The knee has a different axis of rotation at each point of its ROM

As you go from full knee extension to full knee flexion it starts down and moves posteriorly and superiorly

Changes with each point in the ROM

What do the Anterior Cruciate Ligament (ACL) and Posterior Cruciate Ligament (PCL) ensure?

antero-posterior stability of the knee

T/F The ACL and PCL are intercapsular and extrasynovial

True

Located within the joint capsule but outside the synovial lining; Between the synovium and the joint capsule

When is the only time voluntary rotation at the knee can occur?

Voluntary active rotation can only occur when the knee is flexed (ligaments are lax, menisci are free to move)

Can't rotate the tibia on the femur when the knee is fully extended

Which direction will the tibia roll and glide during open chain flexion and extension at the knee? the mensici?

Tibia will roll and glide in same direction

Flexion

• Roll and glide posteriorly

• Menisci will distort posteriorly

Extension

• Roll and glide anteriorly

• Menisci will distort anteriorly

Which is more often damaged: ACL or PCL?

ACL

What are the functions of the PCL?

Prevents:

• Posterior movement of the tibia on the femur

• And anterior movement of the femur on the tibia

• Aids in knee flexion

What is the anterior/posterior draw test?

Patient is in supine, the testing leg has hip and knee flexed, foot flat on the table. Therapist sits on foot to stabilize and wraps hands around proximal end of the tibia.

Anterior Draw Test: Therapist pulls tibia towards himself/herself to test ACL

Posterior Draw Test: Therapist pushes tibia away from himself/herself to test PCL

Too much mobility/instability/pain = + sign

What is the function of the quadriceps femoris group?

Knee extension

made up of:

recutus femoris

vastus medialis

vastus intermedius

vastus lateralis

Name the knee joint bursae, their location and purpose

Purpose of bursae: to decrease frictional forces between muscles, ligaments, and bones

Gastrocnemius bursa (posterior)

Suprapatellar bursa (anterior)

Subpopliteal bursa (posterior)

When can you totally palpate the patella

Full knee extension

What is the most comfortable position of the knee for people with swelling/fluid in the knee?

Semi-flexed position

Flexion and extension will be painful, so this position would be most comfortable

Fluid isn't too far anterior or posterior

T/F Tibia moves laterally during flexion and medially during extension

False

Tibia moves medially during flexion and laterally during extension

• (Similar to the carrying angle at the elbow joint)

Axis for flexion/extension passes horizontally through the femoral condyles obliquely

o Because it's oblique, when we flex and extend our leg, the tibia comes in at an angle

In closed chain kinematics what is moving on what at the knee?

Femur moving on fixed tibia

Sitting down is the same type of motion as __________ the knee.

Flexing the knee

What is the umbrella term that indicates there is some problem at patellafemoral joint?

Chondromalacia patellae

When you get some wear and tear of thick cartilage behind patella which helps to withstand compressive forces

What moves on what in open chain movement at the knee?

Tibia moves on a fixed femur

In open chain kinematics, extending or flexing the knee follows which rule (concave/convex)?

Concave rule: tibia (concave) moves on a fixed femur (convex)

Why are the medial meniscus and MCL more likely to tear than their lateral counterparts?

Because they are more rigidly attached to the knee joint

structures

What is pure spin?

Roll and glide happen simultaneously in opposite directions

T/F Knee rotation can only occur as an automatic movement during the screw home mechanism of the knee

False

Knee rotation is a voluntary movement as well

What direction is the patellofemoral reaction force pulling the patella during knee flexion?

The patella is pulled into the femur

The more and more you flex your knee, the more the

patella gets pushed into the femur

End up with a high joint reaction force

What are the knee flexor muscles and which are 2 joint/1 joint?

7 muscles that flex the knee (all are 2 joint muscles except for the short head of the biceps femoris and popliteus, they only cross the back of the knee joint)

Semimembranosus, Biceps femoris, Semitendinosus, Gracilis, Popliteus, Sartorius, Gastrocnemius

Which direction does the medial meniscus move during knee flexion?

Posteriorly

Which muscle both flexes the knee and laterally/externally rotates the tibia?

Biceps femoris

Which knee flexor muscle acts more on the hip than the knee?

Sartorius

What is the least congruent joint of the body?

Patellofemoral joint

Describe the patella and femoral articulation at the patellofemoral joint during flexion and extension

Full Knee Extension: Patella on the anterior surface of distal femur in the femoral sulcus.

-When you can totally palpate the patella

Flexion: patella sinks into intercondylar notch, mostly disappears

In full knee extension what is the net gain of forces pulling on the patella?

Net gain = 0

Pulled up by the quadriceps up above and pulled down by the patellar ligament down below

So it will get pulled straight up and down

How much compression force is pushing patella into femur during deep knee bends?

7.8 times your body weight

T/F The patella is only stabilized by longitudinal stabilizers

F

The patella is stabilized by transverse as well as longitudinal stabilizers

§ Transverse stabilizers

• Vastus medialis

• Vastus lateralis

• Medial and lateral patellofemoral ligaments

§ Longitudinal stabilizers

• Quadriceps tendon

• Patellar ligament

What can cause too much lateral force on the patella?

Weak vastus medialis

o Because vastus medialis works to keep the patella medially. So if its weak and not doing its job, can be overcome by vastus lateralis and therefore get more lateral movement of the patella

Additionally, if an individual has a lot of genu valgum

o Rectus femoris won't just pull up and down, and instead will pull at an oblique angle laterally

Increased Q angle

Can end up with either a subluxation or dislocation of the patella laterally

Name types of meniscus tears

Tear in posterior 3rd of meniscus

Posterior tear of horn's attachment

Tear halfway to collateral ligament

Complete tear/Bucket Handle tear

What are the symptoms and cause of housmaid's knee/bursitis?

Inflammation (bursitis) of prepatellar bursa and superficial infrapatellar bursa

-both found anteriorly around the patella

Causes:

• Prolonged compressive or tensile stress at the knee

o Being down on your knees all day

• Direct blow to the knee

What happens as a result of MCL rupture?

The two joint surfaces do not line up the way they should

If you have a weak or nonfunctioning quadriceps muscles, what ligaments/muscles can be used to help perform the functions of the quadriceps muscles?

Posterior popliteal capsule along with the Y ligament at the hip can help you to keep both the hip and the knee extended when you don't have a strong quadricep

muscle

Can also use the gastrocnemius muscle

§ If the foot is planted on a surface, it prevents the tibia from moving forward too fast because it wants to pull the tibia back

§ Gastroc/soleus works at the ankle joint to pull the tibia posteriorly thereby helping to stabilize the knee joint and keep the knee fully extended