Kinesiology 2 - Knee Joint (Dr. Holtzman)

What happens to the patella during extension?

Patella moves from: inferior → superior

What happens to the patella during flexion?

Patella moves from: superior → inferior & lateral → medial → lateral again

What is the path of instant center of rotation (PICR)?

Path of the ICR throughout movement *During flexion / extension the PICR is typically an arc

What is typical sagittal plane alignment for the tibiofemoral joint?

Tibia and femur align vertically in 0 - 10 deg of extension

What is normal tibiofemoral abduction & adduction?

Very variable Mean ranges from 2-14 deg

What is adjunct rotation?

When the knee rotates while the knee is flexed Available but doesn't have to be used

How much rotation is available when the knee is fully extended?

0 deg

Possible factors that contribute to the screw-home mechanism

1) Femoral condyle shape 2) ACL passive tension 3) Lateral pull of quadriceps (especially in closed chain)

4 functions of the knee

1) Shortens the LE during the swing phase 2) Provides shock absorption 3) Transmits force through the LE 4) Afford large ranges of motion (running & cutting)

2 joints that make up the knee

1) Tibiofemoral joint 2) Patellofemoral joint

Knee flexion goal post total knee replacement

120 deg

How much internal rotation is available compared to external rotation?

2 times more external than internal

Do we tend to have more movement in the frontal plane at the tibiofemoral joint in flexion or extension?

2-6 deg in extension up to 14 deg in flexion

Typical knee flexion in babies?

20 - 150 deg passive, in neonates 10 - 145 deg passive, in 3 mo 3 - 140 deg passive, in 6 mo

How much rotation is available when the knee is flexed to 90 deg?

25 - 57

Typical adult valgus

5 - 10 degrees

Typical knee flexion in adults?

5-0-155 passive 0-140 active

What is the close packed position of the patellofemoral joint?

90 deg of flexion at tibiofemoral joint

Screw home mechanism during closed chain knee extension

During last 30 deg of extension femur rotates internally on tibia

Screw home mechanism during open chain knee extension

During last 30 deg of extension tibia rotates externally on the femur

What is meant by the phrase "the knee is often an innocent bystander"

Even if the knee itself is ok, it is effected by what is going on at the hip and knee

How much does the patella tilt during flexion and extension?

Extension = slight lateral displacement Flexion < 30 deg = glides & tilts medially Flexion > 30 deg = glides, tilts, & rotates laterally

Of the two bones in the tibiofemoral joint, which is concave & convex?

Femur = convex Tibia = concave

What physiological motions occur at the knee?

Flexion Extension Internal rotation External rotation

Movements allowed at the tibiofemoral joint?

Flexion / extension (large amounts) Rotation (limited amounts) Abduction/Adduction (passively only)

What is open chain movement at the tibiofemoral joint?

Foot not planted on the ground Concave tibia moving on the convex femur

What is closed chain movement at the tibiofemoral joint?

Foot planted on the ground Convex femur moving on the concave tibia

What is the loose packed position of the patellofemoral joint?

Full extension at tibiofemoral joint

When is the contact between the patella and femur greatest?

Full flexion

Which activity puts the most stress on the tibofemoral joint, going up or down stairs?

Going up = 316% of BW Going down = 346% of BW

Describe the knee joint in the sagittal plane during gait

Heel contact = 5 deg flexion *continues to flex 10-15 deg Heel off = full extension *begins to flex again Toe off = 35 deg flexion Mid-swing = 60 deg flexion (max flexion) *extends again

Why is it beneficial to have some physiologic valgus?

Helps us regulate & absorb forces

What is genu recurvatum?

Hyperextension Common in young children but should disappear by adolescence In this position, the person relies on passive structures to stay upright Can cause bowing of the tibia and loss of DF ROM

How is the patella aligned in the intercondylar groove?

In central to slight lateral deviation Slight lateral tilt with knee in extension

Who is more likely to have patellofemoral joint dysfunction, males or females?

Incidence in females is about 2 times as much as males

What is the joint reaction force?

Internal reaction force acting at the contact surfaces when a joint is subjected to external loads

Consequences of an altered PICR?

Joint surfaces do not glide on one another very well

Deviations that occur at the knee during gait?

Knee remains extended (due to weak quads, arthritis) Genu recurvatum (due to habit) Varus thrust (due to ligament laxity, trauma, OA, general LE weakness

What factors can influence Q-angle?

Knee valgus increases, Q-angle increases Patellar medial or lateral deviation Tibial tuberosity anomalies (medial tuberosity causes decreased Q-angle) Femoral anteversion Genu recurvatum Pronation External tibial torsion

Describe movements during internal tibial rotation

Lat. tibial condyle → anterior Med. tibial condyle → posterior Lateral femoral condyle → posterior Medial femoral condyle → anterior Lat. meniscus → posterior Med. meniscus → anterior

Describe movements during external tibial rotation

Lat. tibial condyle → posterior Med. tibial condyle → anterior Lateral femoral condyle → anterior Medial femoral condyle → posterior Lat. meniscus → anterior Med. meniscus → posterior

Ligaments that give the tibiofemoral joint M-L stability

MCL (mostly) LCL PCL ACL

What would happen to the M-L stability of the tibiofemoral joint if there was lesion in the MCL or LCL?

MCL lesion = excessive VALGUS of tibia on femur LCL lesion = excessive VARUS of tibia on femur

Describe the knee joint in the frontal plane during gait

May have slight tibial abduction / adduction during gait cycle (~5 deg)

What is the Insall-Salvati Index?

Measure of patellar proximal-distal alignment = patellar tendon length / patella height Measured at 60 deg flexion Normal = ~1

What are some common misalignments of the patella?

Medial tracking (patella sits too far medially) Lateral tracking (patella sits too far laterally) Patella alta (index >1.2, patella sits high) Patella baja (index <0.8, patella sits low)

Normal Q-angle

Men <10 deg Women > 10 deg

What might alter the PICR?

Meniscal injury Ligament tear ACL reconstruction

What takes the brunt of the JRF at the tibiofemoral joint?

Menisci (50% of BW) Articular cartilage

How do the menisci move when the knee joint rotates?

Menisci follow the femoral condyles

Describe knee osteoarthritis

Meniscus & ACL injury often lead to OA (because injury changes the PICR of the knee, changing joint surface contacts) High correlation between obesity & OA

What is the closed pack position of the tibiofemoral joint?

POSITION: 0 deg extension JOINT SURFACES: max congruence, compression LIGAMENTS & CAPSULE: maximally taught ACCESSORY MOTION: often not possible

What is the loose packed position of the tibiofemoral joint?

POSITION: 25 deg flexion JOINT SURFACES: min congruence LIGAMENTS & CAPSULE: max laxity ACCESSORY MOTION: possible *Often most comfortable after injury

Describe the knee joint in the transverse plane during gait

~ 8-9 rotation between the tibia & femur Heel strike → 20% gait cycle = tibia internally rotates Toe off = tibia externally rotates (locking mechanism) Swing phase = tibia internally rotates

What would happen to the A-P stability of the tibiofemoral joint if there was lesion in the ACL or PCL?

ACL lesion = excessive ANTERIOR displacement of the tibia on the femur PCL lesion = excessive POSTERIOR displacement of the tibia on the femur

Alignment issues that contribute to patellofemoral pain dysfunction

Abnormal patellar positioning Increased Q-angle Increased genu valgum Excessive anteversion of the hip Excessive external tibial torsion

What is the Q-angle?

Angle between lines: 1) ASIS to midpoint of patella 2) Tibial tuberosity and midpoint of patella Describes the resultant force of the quadriceps (tend to pull patella superior & lateral relative to patellar ligament)

Movement of the menisci during open-chain, sitting, knee extension

Anterior

Accessory motions that occur with open-chain, sitting, knee extension

Anterior roll Anterior glide

What takes the brunt of the JRF at the patellofemoral joint?

Articular cartilage Patellar ligament

Functions of the patella

Augment knee extension by displacing the tendon of the quad anteriorly (increases moment arm of knee extensors) Allows wider distribution of compressive stresses on the femur (increases contact between the patellar tendon & the femur)

Guidelines for quadriceps strengthening in patients with patellofemoral pain syndrome

Avoid open chain activities with knee flexion angles 0-45 deg Avoid closed chain activities with knee flexed 60-90 deg These are the ranges at which there is the most stress on the patella

What is the instant center of rotation (ICR)?

Axis of the tibiofemoral joint at a given instant The axis is not constant because of the roll & glide motions that occur at the joint

What type of joint is the tibiofemoral joint?

Bi-condylar joint

Describe tibial torsion

Can be internal or external > 30 deg of external tibial torsion is abnormal

Population that tends to display genu valgus

Commonly seen in older adult females

Describe genu recurvatum

Commonly seen in those with sway-back posture Decreased use & poor muscle performance of the quads & glute max, possible over-recruitment of the hamstrings Can lead to ligamentous laxity

Describe genu varus

More commonly seen in males Can be structural or acquired

Describe the progression of physiologic valgus

Newborns = genu varum that gradually disappears 2.5 - 3 yr = valgus peaks at 12 deg then gradually decreases 6 yr - adult = valgus plateaus by age 6-7

Muscle responsible for unlocking the knee when going into flexion?

Popliteus

Movement of the menisci during closed-chain, knee flexion (stand-to-sit)

Posterior (pushed by the femoral condyles)

Movement of the menisci during open-chain, prone knee flexion

Posterior Semimembranosus pulls medial meniscus Popliteus pulls lateral meniscus

Accessory motions that occur with closed-chain, knee flexion (stand-to-sit)

Posterior roll Anterior glide

Accessory motions that occur with open-chain, prone, knee flexion

Posterior roll Posterior glide

Ligaments that give the tibiofemoral joint A-P stability

Primarily ACL & MCL Also PCL & LCL

Benefits of screw-home mechanism

Provides mechanical stability Allows humans to stand erect without quads contracting Allows human to withstand anterior-posterior forces on the extended knee with reduced muscle force

Result of abnormal Q-angle

Q angle > 15 deg can lead to: -excessive lateral forces on the patella -bowstring effect

Factors that influence JRF on the patellofemoral joint?

Quad muscle force Size of contact area between patella & femur External moment arm of the body segment Position of tibia Other tissues

Muscles that give the tibiofemoral joint A-P stability

Quads Gastroc Hamstrings

What can problems with patellar glide cause?

Restriction in knee joint ROM Instability of patellofemoral joint Pain caused by erosion of the joint surfaces

What accessory motions occur at the knee?

Roll Spin Glide

What type of joint is the patellofemoral joint?

Saddle / sellar joint Convex patella on concave intercondylar groove of femur

Muscles that give the tibiofemoral joint M-L stability

Sartorius, Semimembranosus, Gracilis, ITB, Biceps femoris tendon

Describe tibial varus

Structural