Kines - Biomechanics of the Knee

✤1° Function: Passive restraint of ✤Anterior translation of the tibia on femur ✤Provides 85% of the restraining force ✤Posterior translation of the femur on tibia(only in closed chain) ✤2° Function: Passive restraint of ✤Internal & external tibial rotation ✤Varus & valgus stresses ✤Hyperextension

ACL

✤Lie in the center of the tibiofemoral joint ✤They form a cross when viewed from the side, but are parallel when viewed from above ✤Both are intracapsular, but extrasynovial ✤Working together they resist extremes of all knee movements ✤Most focused on resisting anterior and posterior sheer forces of the tibia on femur ✤Guide the natural arthrokinematics of the knee ✤Contribute to proprioception of the knee

ACL and PCL

✤Medial-lateral ✤Moves within the femoral condyles ✤Average position: lateral epicondyle

AOR flex/ext

______ axis is the oblique alignment of the femoral shaft going medially toward the knee creating the valgus angle. Mechanical axis is representing the ______ ______ ______ which follows Newton's 3rd law of equal and opposite forces. Whenever you're standing the force is equally distributed in between the medial and lateral portion of the knee while in single leg stance, the line of gravity will shift to the ______ tibial condyle.

Anatomical, ground reaction force, medial

The femur is oriented _______. Because of the 125 degree angulation created by the femoral neck, the femur has an _____ angulation and points medially to meet the tibia. As a result, a _____ force/angle is created at the knee.

Angularly, oblique, valgus

The knee has ____ bursae. The two main ones are the ______ and ______ bursae. These structures reduce ______ between moving parts of the body.

12, suprapatellar, infrapatellar, friction

The knee complex joint capsule is most relaxed between _____ and _____ degrees of knee flexion. Whenever patients come in after ACL repairs, you find a lot of swelling you would want to position them in this open pack position to allow the body to naturally reabsorb the fluid.

15, 30

✤Normal frontal plane genu valgus: ✤Excessive genu valgus "knock-knee": ✤Genu varum "bow legged":

180-185, >185, <175

The unlocking of the knee occurs in the initial ___° of flexion. In open chain, the tibia rotates _______. In closed chain the femur rotates ______. This is driven by the concentric contraction of the ______ muscle which can drive these rotations. This mechanism allows the knee to exit the ______ packed position and produce functional movement.

20, internally, externally, popliteus, closed

During the last ____° of knee extension, the ______ ______ mechanism locks the knee in a stable position. In open chain, the ______ rotates externally. In closed chain, the _______ rotates ______. This mechanism is driven by the shape of the ______ condyle, the passive tension of the ______, and slight _______ pulls of the vastus lateralis. This maximizes the overall contact area of the knee, improves ______, and favors _____.

20, screw home, tibia, femur, internally, medial, ACL, lateral, congruency, stability

Initial flexion of ___° will cause the patella to slide into the trochlear groove.

25

Whenever the femur rolls posteriorly, there is a relative _______ translation of the tibia. This will be checked by _____.

Anterior, ACL

The ______ surface of the patella is convex in all directions. The posterior surface has a _______ ridge that runs from base to apex and divides the patella into 2 facets. This ridge corresponds to the trochlear groove on the ______. There is also a _____ ridge that runs from medial to lateral.

Anterior, vertical, femur, horizontal

During open chain extension of the knee, the tibia simultaneously rolls and slides ______ on the femoral condyles. The menisci slide ______ or back to neutral. As the quads contract concentrically, the patella is pulled ______.

Anteriorly, anteriorly, superiorly

In the suprapatellar pouch, whenever you move the knee into extension the synovial fluid will go ______. Whenever you move the knee into flexion the synovial fluid will go ________.

Anteriorly, posteriorly

In closed chain extension of the knee, the femoral condyles simultaneously roll ______ and slide _______ on the articular surface of the tibia. The quadriceps creates the roll of the femoral condyles. Menisci slide ______ ahead of the rolling femoral condyles. Patella slides ______.

Anteriorly, posteriorly, anteriorly, superiorly

The tibial tuberosity can be _____ by the quads due to irritation. This is known as Osgood Schlatters.

Avulsed

The quadriceps tendon attaches to the _____ of the patella. The patellar tendon attaches to the apex of the patella and the ______ ______.

Base, apex, tibial tuberosity

Depends on knee position 20°

IR tibia

There is a gradual _______ in contact between the patella and the trochlea groove during knee flexion. At no point does more than ____ of the patella come in contact with the femur. Maximal patella to femur contact area occurs between ___-___°. Maximal compressive force exerted on the patella occurs between ___-___°. The "large" contact area between the patella and femur disperses the large _______ force generated by the quadriceps so that stress upon the articular cartilage does not rise to intolerable physiologic levels.

Increase, 1/3, 60-90, 60-90, compressive

As you move into knee flexion, the patella slides _____. Within the first 30° of knee flexion the patella translates medially ____ mm. At around 45° of flexion the patella begins to translate ______. By 90°of knee flexion the patella has translated back laterally ___ mm. There will also be a slight _____ patellar TILT.

Inferiorly, 2.8, laterally, 2, lateral

Posterior femur where the medial and lateral condyles are separated

Intercondylar notch

✤Between the two tibial condyles ✤Attachment points for both menisci and both cruciate ligaments (ACL and PCL)

Intercondylar region

✤The capsule is supported by: ligaments, retinacular structures, and muscles/tendons ✤Two layers ✤Outer: fibrous ✤Inner: Synovial sheath inside the joint ✤Not adhered to one another

Knee joint capsule

✤Resists genu varus forces ✤A force that tends to adduct the distal segment of a joint ✤In extension resists 50% of varus forces ✤In 25° of flexion resists 70% of varus forces

LCL

The ______ _____ of the femur lies more in line with the shaft than the medial condyle. It projects ______ more than the medial condyle and helps stabilize the _____ in the trochlear groove. This creates a passive stability for the ______ and decreases lateral tracking.

Lateral condyle, forward, patella, patella

✤Restrains medial patellar movement ✤Lateral patellofemoral ligament lies deep to medial retinaculum lateral retinaculum

Lateral retinaculum

In genu valgum, compressive forces will be seen on the _____ tibial condyle and tibial plateau. Tensile forces will occur on the _____ side which will affect the ______ _____, ____, ____, and ____ muscles.

Lateral, medial, medial meniscus, MCL, ACL, SGT

The _______ condyle of the tibia is nearly flat and very slightly concave. It is ______ than the medial condyle.

Lateral, shorter

The knee ______ and ______ the lower extremity. As such, it assists the hip in positioning the foot in space or the ground during ______. The knee is a critical motion segment for producing _____ movement such as sit to stand, stair negotiation, and sports. It supports the superincumbent body weight in erect standing with minimal ______ activity. It also maintains _______ and produces motion while managing ground reaction forces.

Lengthens, shortens, gait, functional, muscle, stability

In knee extension, the medial femoral condyle and medial tibial plateau is ______ anterior to posterior which has an application to the locking mechanism.

Longer

✤A force that tends to abduct the distal segment of a joint ✤In extension resists 60% of valgus forces ✤In 25° of flexion it resists 80% of valgus forces ✤Twice as strong as the LCL and can sustain larger valgus loads ✤Injured more often than LCL

MCL

The _____ _____ of the femur is larger and extends further distally. As this structure is taller than the lateral femoral condyle, it helps create the _____ angle at the knee. It is longer in the ______ to ______ direction which impacts the osteokinematics of the knee joint. For example, the rotation created in knee extension is due in part to the _____ of this structure. The tibial plateau is _____ to counteract rotational force.

Medial condyle, valgus, anterior, posterior, length, neutral

✤Restrains lateral patellar movement ✤Medial patellofemoral ligament lies deep to medial retinaculum

Medial retinaculum

✤Pes anserine line ✤Attachment point for pes anserine tendon (SGT muscles)

Medial tibia

The _______ condyle of the tibia is larger and slightly concave. It is longer in the ________ direction than the lateral condyle.

Medial, anterposterior

The _____ meniscus is C shaped while the ______ is O shaped The ______ is less mobile which contributes to higher incidence of tears in this structure. The semimembranosus attaches to the _____ meniscus while the _____ attaches to the _____ meniscus.

Medial, lateral, medial, medial, lateral

The _____ facet of the patella has an anatomically variable shape. A structure referred to as the "_____ facet" is located at the extreme medial border. The articular cartilage in this region is 4-7 mm thick to help sustain the joint against contact forces. The _____ facet is larger than the medial.

Medial, odd, lateral

The _____ angle or quadriceps angle produces lateral force on the patella and corresponds to genu valgum and varum. Separate this angle from the _____ variation of the tibia and the femur cause it's the ______ force that creates the angle.

Q, structural, muscle

The outer one third of the meniscus is vascularized by a branch of the popliteal artery and is referred to as the ______ zone. As a result, this area will _____ better. The inner two thirds of the meniscus is poorly vascularized but receive nutrition from the ______ fluid by the process of diffusion.

Red, heal, synovial

✤Superficial tendinous extensions of the vastus medialis, vastus lateralis, and iliotibial band ✤Extensive, attaching to: femur, tibia, patella, menisci, collateral ligaments, and patellar tendon

Retinacula

The _____ blend with patellofemoral ligaments. Because it's a ______ structure and attaches to vastus lateralis and medialis it can also create passive stabilization of the patella. Depending on the side it sits on it will be able to block ______ motion. Lateral will block medial patella translation and vice versa. If these structures are loose the patella will have more _____.

Retinacula, passive, patellar, ROM

Open chain motion of the knee involves movement of the ______ on the _______. This follows a ______ on ______ pattern of movement.

Tibia, femur, concave, convex

✤Convex femoral condyles articulating with flat/concave tibial condyles (because we have the meniscus not making it bone on bone) ✤Synovial: modified hinge ✤Degrees of freedom: 2 -Flexion & Extension -Internal & External Rotation ✤Divided into 2 compartments -Medial & lateral

Tibiofemoral joint

The knee complex refers to the _______ joint and the _______ joint. These two joints share one capsule, while the _____ joint has it's own capsule.

Tibiofemoral, patellofemoral, tibiofibular

During flexion the patella flexes as the inferior pole tips forward ______ the tibia. During extension the patella extends as the inferior pole tips _____ from the tibia.

Toward, away

✤Anterior union of both femoral condyles ✤The lateral femoral condyle has a steeper groove than the medial condyle ✤Site of articulation for the patella

Trochlear groove

Depends on knee position 20°

ER tibia

The patella is most mobile in full knee ______.

Extension

The open packed position of the PF joint is in full knee ______ when the patella sits outside of the trochlear groove and the ______ are relaxed. The closed pack position occurs when maximum contact between the patella and femur occurs at ___°.

Extension, quads, 90

The vertical axis of rotation of the hip runs from the ______ head to the center of the ______. That axis of motion can be extended further inferior from the center of the knee to the ______ and ______. This is important as this axis mechanically links the transverse plane movements of the 3 major joints of the lower extremity.

Femoral, knee, foot, ankle

Closed chain motion of the knee involves movement of the ______ on the _______. This follows a ______ on ______ pattern of movement.

Femur, tibia, convex, concave

The knee joint capsule encapsulates the ______, ______ and _____. Synovial fluid is present in the joint for lubrication and ______ of the joint.

Femur, tibia, patella, nutrition

✤NOT part of the knee joint ✤It is an important attachment point for the -Biceps femoris -Lateral collateral ligament

Fibula

The open packed position of the TF joint is in 25° of knee _____. The closed packed position is in full knee _____ and tibial _______ ______ via the screw home mechanism and ligamentous tightening.

Flexion, extension, external rotation

✤Protect the articular cartilage ✤Reduce compressive stress across tibiofemoral joint ✤Create a concavity for the convex condyles ✤Improves joint congruency ✤Improves joint stability ✤Improves surface contact area ✤Promote lubrication of articular cartilage ✤Block joint capsule from entering the joint space ✤Assists in driving the arthrokinematics of the tibiofemoral joint ✤Restrain excessive movement such as hyperextension ✤Provides proprioceptive information

Functions of meniscsi

✤Crescent-shaped fibrocartilaginous discs which sit on the tibial condyles / ✤Cover 50% of the tibial plateau ✤Wedge shaped when viewed anteriorly ✤Vascularity: Poor, except for peripheral border ✤Attach to intercondylar eminence of tibia

Menisci

✤Angle of inclination of femur: 125° ✤Shaft of femur angles slightly medially as it descends to the knee ✤Medial femoral condyle is slightly longer than the lateral condyle ✤Creates a slight frontal plane valgus alignment between femur and tibia

Natural knee valgus

✤1° Function: Passive restraint of: ✤Posterior translation of the tibia on femur ✤Anterior translation of the femur on tibia(closed chain only) ✤2° Function: Passive restraint of ✤Internal & external tibial rotation ✤Varus & valgus stresses ✤Hyperextension

PCL

✤Triangular sesamoid bone ✤Superior: Curved"base" ✤Inferior: Pointed"apex"

Patella

The _______ increases the moment arm and thus torque generating potential of the quadriceps by 30%. This structure _______ the forces of the 4 quadriceps muscles into one concentrated line of pull. Protects the quadriceps from excessive ______ during knee flexion.

Patella, centralizes, friction

The tibial tuberosity serves as the attachment site for the _____ tendon. It appears as a large, roughened area.

Patellar

From full extension to full flexion ✤0° Extension: Patella is located proximal to the tibiofemoral joint resting on the supra and infrapatellar fat pads (standing) ✤10-20° of Flexion: Patella is drawn into the trochlea groove (moving into flexion) ✤20-30° of Flexion: Inferior pole of the patella makes contact with the femur ✤45-60 ° of Flexion: Center of the patella is in contact with the femur ✤60 - 90° of Flexion: Upper 1/3 of the patella is in contact with the femur and the patella is maximally situated in the trochlear groove at 90° ✤100-120° of Flexion: Contact area moves to the lateral and medial edges of the patella, as the patella begins to form a bridge over the trochlea notch ✤>130-135° of Flexion: The patella forms a "bridge" over the trochlea notch with only the "odd facet" and lateral edge of the patella making contact with the femur

Patellar contact forces

Patella articulating with the trochlear groove of femur and femoral condyles

Patellofemoral joint

The proximal end of the tibia flares out, forming the tibial ______.

Plateau

The tibial ______ is predominantly flat with slight convexity at the anterior and posterior margins.

Plateau

During closed chain knee extension, there will be a relative ______ translation of the tibia. This will be checked by _____.

Posterior, PCL

In closed chain flexion of the knee the femoral condyles simultaneously roll _______ and slide _______ on the articular surface of the tibia. Quadriceps _______ control the rate of rolling of the femoral condyles. Patella slides _______.

Posteriorly, anteriorly, eccentrically

In open chain flexion of the knee, the tibia simultaneously rolls and slides _______ on the femoral condyles. The menisci slide ______ and the patella slides ______.

Posteriorly, posteriorly, inferiorly

The main function of the knee joint is _____ _____ during weight bearing. During walking, the knee helps absorb _____ and assists in clearing the foot from the ground. The knee produces flexion ______ and extension ______ when you step on the foot. The hip, knee, and ankle work together to lengthen and shorten the lower extremity and propel the body forward.

Shock absorption, shock, concentrically, eccentrically

Clinically, we know the axis of rotation doesn't stay perfectly ______ so you know there will be a degree of error whenever you do goniometry. Also, if the axis of rotation is constantly migrating, mechanically the lever arm of the _____ will be changing too and this will cause us to produce more force or less force.

Stationary, muscle

✤Pouch created by synovial layer located about 5 cm proximal to patella ✤Becomes enlarged/swollen when the knee joint is injured ✤Excess fluid enters during extension and leaves during flexion

Suprapatellar bursa