Knee Part 2
The patellofemoral joint is exposed to high compression forces. - _____x BW during walking on level surfaces - _____x BW during straight leg raise - _____x BW climbing stairs - _____x BW deep squats
- 1.3 - 2.6 - 3.3 - 7.8
Isolated PCL tears are rare. _____% of knee injuries are PCL tears and usually _____% involve other knee structures, such as the meniscus, ACL, and posterolateral capsule.
- 2-10% - 50%
As knee extends to _____ of flexion, contact area of the patella migrates to the inferior pole of the femur and with full _____, the patella rest proximal to trochlear groove.
- 20º - extension
External torques placed on the knee vary with knee angle and limb orientation. To reduce the external torques and still strengthen the quads while minimizing stress on the patellofemoral joint: - Tibial-on-femoral knee extension—LAQ—should stay in the _____ degree range. - Femoral-on-tibial knee extension—partial squat—should stay in the _____ degree range.
- 90-45º - 45-0º
What are some potential causes of an ACL tear?
- anatomy - hormonal fluctuations - strength - neuromuscular control
What are the 2 bundles of the PCL?
- anterolateral bundle (ALB) - posteromedial bundle (PMB)
With relation to the ACL, collagen fibers twist around each other forming which two bundles? Also named for their attachments to the tibia.
- anteromedial bundle (AMB) - posterolateral bundle (PLB)
One of most important influences on PF joint biomechanics is the magnitude and line of pull of the quads. As the knee is extending, the line of pull on the patella is superior on trochlear groove, but also slightly laterally and posteriorly. Lateral pull is the result of larger _____ and _____.
- cross-sectional area - force of vastus lateralis
The normal alignment of the knee is in the _____ plane and _____ degrees of valgus.
- frontal - 5-10 degrees
In the sagittal plane, _____ is the closed-packed position of the knee. This is the most stable position. Normal hyperextension of _____ degrees may occur.
- full extension with ER - 5-10 degrees
Which muscles are included in the knee flexor-rotator group?
- hamstrings (biceps femoris, semimembranosus, semitendinosus) - sartorius - gracilis - popliteus
Additional MOI of an ACL injury is excessive _____ while the foot is planted on the ground. Excessive _____ slide of the femur on the fixed tibia overstretches/ruptures the ACL.
- hyperextension - posterior
With internal torque-joint angle relationship of the quads, the shape of the curve will depend on the type and speed of contraction and position of the hip. In this study, similar results were produced: - max effort is with _____ contraction with the hip fixed in _____ - 90% of max is between _____ and _____ degrees
- isometric - extension - 80 and 30º
The extensors perform multiple functions at knee including which actions?
- isometric action - eccentric action - concentric action
The magnitude of the external torque is highly dependent on the specific manner in which the knee is being extended. - Tibial-on-femoral extension is _____ kinematics. - Femoral-on-tibial extension is _____ kinematics.
- opened - closed
Clinically, this stress of exercise that challenges the quads may be potentially damaging or therapeutic, depending on underlying pathology (if any). Patients with _____ joint pain or _____ are usually advised against large amounts of muscular stress on the knee. In contrast, healthy patients in later phases of _____ rehab may benefit from larger stresses.
- patellofemoral - osteoarthritis (OA) - ACL
L3-L5 spinal nerve roots travel to the spinal cord primarily through which 3 nerves?
- posterior tibial nerve - obturator nerve - femoral nerve
PF joint compression force is influenced by both _____ force and knee _____ angle.
- quad - flexion
What are the parts of the knee extensor mechanism?
- quadriceps - patella - patellar tendon
The patella is held relatively stationary by the balance of forces between the eccentric pulling of _____ and the _____.
- quadriceps - patellar tendon
What are the knee extensors?
- quadriceps femoris - rectus femoris - vastus group (lateralis, medialis, intermedius) - articularis genu
As the knee flexes and extends, the patella is pulled superiorly by the _____ and inferiorly by the _____— the combination increases posterior compressive force of the patella on the femur. This increases as knee flexion increases.
- quads - patellar tendon
Failure of the patella to glide, tilt, shift, or rotate appropriately can lead to what?
- restrictions in knee ROM - maltracking - pain from compression of PF articular surfaces
What are the three factors that affect knee extension MA in sagittal plane motion?
- shape and position of patella - shape of distal femur (depth of trochlear groove) - migrating medial-lateral axis of rotation at knee (evolute)
The following oppose the lateral pull on the patella: - lateral facet of _____ (steeper slope) - vastus medialis oblique fibers - medial patellar retinaculum fibers (_____ ligament)
- trochlear grove - medial PF ligament
Global factors are related to the alignment of the bones and joints of the LE, especially in the horizontal and frontal planes. Any factor that resists excessive _____ or extreme _____ of the tibiofemoral joint favors optimal tracking of the PF joint.
- valgus - axial rotation
The PCL has a _____% greater cross-sectional area than the ACL which accounts for the PCL resisting greater loads before failure.
120-150%
Q-angle increases with greater lateral pull on the patella. The average in adult is _____ degrees (+/- 4.5 degrees)
13-15 degrees
At _____ degrees of flexion, the patella contacts the femur near its superior pole (A). In this position, the patella is well below the trochlear groove (D).
135º
The knee extensors are capable of producing very large forces; they produce _____ greater torque than the flexors.
2/3
When is the MA of the knee extensor mechanism greatest?
20-60° of flexion
With internal torque-joint angle relationship of flexors, maximum flexion torque is greatest in the last _____ degrees of full knee extension. It steadily declines with increased flexion.
20º
Maximum anterior translation of the tibia occurs at _____ where neither the anteromedial bundle (AMB) or the posterolateral bundle (PLB) is fully taut.
30 degrees flexion
Where does the PCL become slack?
30-40° of flexion
With internal torque-joint angle relationship of the quads, maximum knee extension torque occurs between _____ and _____ of flexion with the hip fixed in extension. Less torque is produced at near extremes of flexion and extension.
45 and 70º
With internal torque-joint angle relationship of flexors, the greatest flexor MA (leverage) is from _____ to _____ degrees of flexion.
50 to 90º
Both the compression force and area of articular contact of the PF joint increase with flexion, and is greatest between _____ degrees, where the stress is also greatest. Protects the joint against stress-induced cartilage degeneration.
60-90º
Where is the anterolateral bundle (ALB) of the PCL taut?
80-90° flexion
Where is peak tension of the PCL? This explains why injuries usually involve significant knee flexion.
90-120° flexion
As knee extends toward _____ degrees of flexion, the contact region of patella migrates toward the femur's inferior pole (B).
90º
Between _____ and _____, patella is engaged within the trochlear groove; this is the greatest contact area.
90º and 60º of flexion
The female to male incidence of ACL injury is reported as high as _____ depending on the sport.
9:1
Mechanism of injury of the _____ includes: - valgus stress with foot planted - axial rotation of knee with foot planted - any combination of valgus stress and axial rotation with foot planted, especially combined with strong quad contraction and knee in full or near-full extension - severe hyperextension
ACL
Most _____ tears involve injuries to other structures as well which results in secondary trauma to other tissues (bone, articular cartilage, menisci, or MCL).
ACL
The force from contraction of the quadriceps during the last 50-60 degrees of knee extension pulls the tibia anteriorly driving the anterior slide portion of the arthrokinematics. The _____ limits the anterior slide.
ACL
What is the most frequently totally ruptured ligament of the knee? 1/2 are in people between 15 and 25 years of age, and it will not heal on it's own.
ACL
What is the primary restraint to anterior translation of the tibia on the femur?
ACL
What provides rotary stability of the knee during IR/ER, varus/valgus angulations, and combinations of these motions?
ACL
Which ligamnets attaches to the anterior intercondylar area of tibial plateau and runs obliquely in a posterior, superior, and lateral direction to attach on medial aspect of lateral femoral condyle?
ACL
Which cruciate ligaments cross within the intercondylar notch of the femur?
ACL and PCL
What is the origin of the rectus femoris?
AIIS
One of the factors associated with non-contact ACL injury is excessive _____ of the knee. The femur is excessively rotated internally at the hip relative to the fixed tibia.
ER
Excessive tension produced by the _____ and the lateral patellar retinacular fibers act directly on the PF joint.
IT band
Which nerve roots give sensory innervation of the knee and associated ligaments?
L3-L5 spinal nerve roots
Mechanism of injury of the _____ includes: - varus stress with foot planted - severe hyperextension of knee
LCL
Mechanism of injury of the _____ includes: - valgus stress with foot planted - severe hyperextension of knee
MCL
Injury to the _____ is usually associated with high-energy trauma, such as falling onto a fully flexed knee when the tibia strikes the ground first.
PCL
Mechanism of injury of the _____ includes: - dashboard injury - falling on fully flexed knee (especially with ankle plantarflexed), such that the proximal tibia hits the ground first - large axial rotation or valgus-varus torque to the knee with the foot planted, especially while the knee is flexed - severe hyperextension
PCL
Posterior translation of the tibia is limited by tension of the _____.
PCL
What is the primary restraint to posterior translation of the tibia on the femur?
PCL
What provides secondary restraint to varus/valgus stresses and excessive axial rotation?
PCL
Which cruciate ligament is shorter and less oblique?
PCL
Which ligament attaches from the posterior intercondylar area of tibia to the lateral aspect of the medial femoral condyle?
PCL
The patellar tilt is named by the direction the _____ surface of patella moves relative to femoral condyles. Example: Lateral tilt occurs when the lateral edge of patella approximates the lateral femoral condyle.
anterior
Which is the larger of the 2 bundles of the PCL?
anterolateral bundle (ALB)
The patella rotates around an A-P axis and creates a medial or lateral rotation. Referenced by the movement of the _____ of the patella. Example: Medial rotation occurs when patella spins with the apex of patella pointing toward medial femoral condyle; the base of patella laterally rotates toward the lateral femoral condyle.
apex
Which muscle is poorly defined and located deep to the vastus intermedius?
articularis genu
Which muscle pulls the capsule and synovial membrane proximally during knee extension?
articularis genu
Lateral pull of quads produces a _____ force on the patella which has the tendency to pull the patella over a region of reduced contact area. This increases stress and likelihood of dislocation.
bowstringing
Which nerve innervates the short head of the biceps femoris?
common peroneal portion of the sciatic nerve (L5-S2)
Which action of the knee extensors accelerates the tibia or femur toward knee extension, raising the body's COM when running uphill, jumping, or standing from seated position?
concentric action
_____ means "cross shaped."
cruciate
Acting together the _____ provide multiplanar stability by resisting all extreme movement of the knee.
cruciate ligaments - ACL and PCL
With femoral-on-tibial knee extension, external MA _____ from 90 to 0º (D-F).
decreases
What is an example of femoral-on-tibial movement?
descending into a squat
Which action of the knee extensors controls the rate of descent of body mass (decelerate flexion) when sitting, squatting, or landing from a jump?
eccentric action
Which action of the knee extensors provides shock absorption when running or landing by controlling knee flexion; acts as a spring to dampen impact of loads on joints?
eccentric action
_____ can alter patellar tracking and increase stress on ACL, MCL, and medial capsule; this increases compressive forces on lateral compartment.
excessive genu valgum
_____ can be due to several risk factors, such as previous injury, genetics, high BMI, laxity of ligaments, abnormal alignment or weakness at proximal or distal LE (weak hip abductors or increased foot pronation).
excessive genu valgum
_____ is also known as knock-knee.
excessive genu valgum
Normally standing with the knee fully _____ directs the LOG slightly anterior to the medial-lateral axis of rotation at the knee. Gravity produces a slight external torque which allows locking of the knee so the quads can rest. This is normally permitted by passive tension in the posterior capsule and stretched flexors.
extended
_____ is the inability to actively complete full tibial-on-femoral knee extension.
extensor lag
During upright activities an _____ torque acts on the knee.
external (flexor)
Do males or females have a higher incidence of ACL tear?
females
_____ are more likely to land with knees in greater valgus which places a large tensile load on the ACL and MCL. This may result from decreased neuromuscular control and/or decreased muscle strength.
females
Which nerve supplies most of the anteromedial and anterolateral capsules of the knee?
femoral nerve
Which nerve innervates the quadriceps femoris?
femoral nerve (L2-L4)
Which nerve innervates the sartorius?
femoral nerve (L2-L4)
What are the 3 sources of innervation of the knee flexor-rotator group?
femoral, obturator, and sciatic nerves
Which movement involves the trochlear groove of the femur sliding relative to the fixed patella?
femoral-on-tibial
With internal torque-joint angle relationship of the quads, the range of max quad torque potential corresponds to many functional activities of _____ motion, such as rising from chair, ascending steps, and squatting.
femoral-on-tibial
At 135º of flexion, when the patella contacts the femur near its superior pole (A) and the patella is well below the trochlear groove (D), the lateral edge of the lateral facet and odd facet articulate with the _____.
femur
The tension of the ACL changes as the knee _____ and ______, so at any given point throughout the sagittal plane ROM, some fibers remain relatively taut.
flexes and extends
Females have a decreased knee _____ angle when landing; quad dominant.
flexion
The PCL remains taut during most of flexion and extension, but the majority of the PCL becomes increasingly taut with greater knee _____.
flexion
When flexing the knee against gravity, such as when lying prone, contraction of the _____ actively slides the tibia posteriorly relative to the femur.
flexors
The patella translates medially and laterally and creates a medial or lateral shift in the _____ plane. Example: lateral shift is the patella moving toward lateral femoral condyle.
frontal plane
Where is the posteromedial bundle (PMB) of the PCL taut?
full extension
All muscles that cross posterior to the knee have the ability to flex and IR or ER the knee except the _____.
gastrocnemius
_____ can occur from generalized laxity or can be from chronic, overpowering knee extension torque which leads to overstretching of the posterior structures; this may stem from poor postural control or from NM disease causing spasticity of quads and/or paralysis of the knee flexors.
genu recurvatum
_____ is hyperextension greater than 10 degrees.
genu recurvatum
Excessive _____ due to weight bearing activities can increase Q-angle and bowstringing force. This often occurs with excessive IR of the femur on a fixed tibia: - weakness or decreased NM control of hip ERs/abductors - tightness of hip IRs - compensation for excessive anteversion - excessive external tibial torsion
genu valgum
During ambulation, ground reaction force passes medial to the A/P axis of the knee creating varus torque which can lead to incidence of medial compartment OA of knee. As cartilage thins, it can tilt the knee into _____ which increases medial compartment loading.
genu varum
_____ is also known as bow-legged.
genu varum
Many strengthening exercises are designed to work the quads with resistive, external torques using only _____ acting on the body.
gravity
Flexing the hip elongates the _____ promoting greater knee flexion torque.
hamstrings
Which muscle group would be an "ACL agonist"?
hamstrings
Which muscles are PCL antagonist?
hamstrings
With internal torque-joint angle relationship of flexors, the _____ generate the greatest torque at knee with relative elongation rather than high leverage.
hamstrings
The oblique and crossed orientation of the cruciate ligaments allow stabilization in the _____ and _____ planes: twisting or cutting motions. Tension helps guide the natural arthrokinematics, especially related to restraint of sliding motions between tibia and femur.
horizontal and frontal planes
When does the MA of the knee extensor mechanism decline significantly?
in last 30° of knee extension (decreased MA and muscle length)
With tibial-on-femoral knee extension, external MA of the weight of the LE _____ from 90 to 0º of knee flexion (A-C).
increases
ACL injury leads to knee _____.
instability
The external flexor torque must be met or exceeded by opposing _____ torque.
internal (extensor)
the force the muscle has to produce to resist the force being applied
internal (extensor) torque
Cruciate ligaments are _____ and covered by a synovial membrane; they have relatively poor blood supply.
intracapsular
Which action of the knee extensors stabilizes and protects the knee?
isometric action
The _____ is the perpendicular distance between the medial-lateral axis of rotation and LOF of muscle.
knee extensor internal MA
When does extensor lag usually occur? It is due to weak quads, and can be fully extended during passive knee extension.
last 15-20º of active extension
Because the apex of the patella is attached to the tibial tuberosity it follows the tibia when knee is flexed (OKC). The tibia moves lateral; therefore, the apex of patella moves _____.
lateral
With femoral-on-tibial knee extension, _____ quad force is required as knee approaches 0º extension.
less
The cruciate ligaments contain _____ which provide the nervous system with proprioceptive feedback; plays a protective role by reflexively limiting muscle activation that may damage ligaments.
mechanoreceptors
With tibial-on-femoral knee extension, _____ quad force is required as the knee approaches 0º degrees of extension.
more
Another MOI of the PCL might be a _____ which drives the proximal tibia posteriorly relative to the femur.
motor vehicle accident (dashboard injury)
Where does the posterolateral bundle (PLB) of the ACL become more taut?
near full extension
70% of ACL tears are _____, such as landing from a jump, cutting or pivoting maneuvers, or quick and forceful deceleration.
non-contact (or minimal contact)
Which nerve supplies sensation from the skin over the medial knee and posterior/posteromedial capsules of the knee?
obturator nerve
Which nerve innervates the gracilis?
obturator nerve (L3-L4)
What is the origin of the vastus group?
on the femur
movement between the patella and femur across the greatest possible area of articular surface with least possible stress
optimal patellar tracking
Chronic instability of the knee leads to degenerative changes and early onset of _____.
osteoarthritis (OA)
Lateral shift of the patella is used during _____ test.
pat apprehension test
As the knee flexes and extends, the _____ slides over the trochlear groove of the femur.
patella
The _____ augments the extension torque at the knee (T = F x MA). This changes during flexion and extension.
patella
The _____ functions as a spacer between femur and quads.
patella
The _____ increases internal MA of the knee extensor mechanism.
patella
What acts as an anatomical pulley for the quadriceps and reduces friction between patellar tendon and femoral condyles?
patella
interface between the articular surface of patella and the trochlear groove of femur
patellofemoral joint
Mechanism of injury of the _____ includes: - hyperextension or combined hyperextension with ER of knee
posterior capsule
Which nerve supplies sensation to posterior capsule of the knee and associated ligaments and most internal structures of knee?
posterior tibial nerve
Exercises that challenge the _____ also stress the knee and patellofemoral joint, and its periarticular connective tissues (such as the ACL).
quadriceps
One of the factors associated with non-contact ACL injury is strong activation of the _____ over a slightly flexed or fully extended knee.
quadriceps
The contraction force of the _____ at relatively low flexion angles stretch (antagonize) the ACL.
quadriceps
Which muscles are "ACL antagonist"?
quadriceps
The _____ has a cross-sectional area that is 2.8x larger than the hamstrings.
quadriceps femoris
The quadriceps merge to form the _____ which inserts on base and sides of patella and continues to form patellar tendon, from the apex of the patella to the tibial tuberosity.
quadriceps tendon
Which knee extensor is the only one that crosses hip and knee?
rectus femoris
Which muscle produces 20% of the torque of the knee extensors?
rectus femoris
Which muscle produces hip flexion and knee extension?
rectus femoris
Adding forceful contraction of quads to existing hamstrings contraction _____ strain on the PCL.
reduces
Swelling or effusion increases the likelihood of developing extension lag due to increased intra-articular pressure of knee and reflexively inhibiting neural activation of quads; this is known as _____.
reflex inhibition
The cruciate ligaments work primarily in the _____ plane—resist anterior and posterior shear forces between the tibia and femur during activities such as walking, running, squatting, or jumping.
sagittal
Genu recurvatum occurs in the _____ plane.
sagittal plane
A _____ can also increase the likelihood of lateral tracking/dislocation of the patella.
shallow trochlea
As knee extends to 20º of flexion, contact area of the patella migrates to the femur's inferior pole and with full extension, the patella rest proximal to the trochlear groove. Here, the quadriceps are relaxed and the patella can move freely. Most _____ or _____ occur laterally in this position because of the line of pull of quadriceps.
subluxations or dislocations
Maximum internal torque potential is least near _____ while opposing external flexor torque is greatest.
terminal extension
Because of the attachment of the patellar tendon to the tibial tuberosity, the patella follows the _____ during flexion.
tibia
Cruciate ligaments are named according to their attachment to the _____.
tibia
Which nerve innervates the popliteus?
tibial nerve (L4-S1)
Which nerve innervates the gastrocnemius?
tibial nerve (S1-S2)
Which nerve innervates the hamstring muscles except short head of biceps femoris?
tibial portion of the sciatic nerve (L5-S2)
Which movement involves the patella sliding relative to the fixed trochlear groove of the femur?
tibial-on-femoral
_____ and _____ are necessary for the patella to remain seated as the femur rotates on the tibia.
tilt and rotation
A non-contact ACL injury is marked by _____ of the knee.
valgus collapse
Which muscle produces 80% of the torque of the knee extensors?
vastus group (lateralis, medialis, intermedius)
Which muscle produces only knee extension?
vastus group (lateralis, medialis, intermedius)
Which muscle of the vastus group has a longus and obliquus part?
vastus medialis
The patella tilts around a _____ axis and creates a medial or lateral patellar tilt.
vertical axis
The knee flexor-rotator group muscles function during _____ and _____ activities.
walking and running
Where does the anteromedial bundle (AMB) of the ACL become more taut?
when flexion > 15 degrees
