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