Biomechanics Quiz 2a

The muscles of the knee are innervated by which 3 different nerves:

(1) femoral, (2) sciatic, and (3) obturator

The sciatic nerve has two branches:

(1) tibial and (2) peroneal.

Normal alignment (hip and knee)

5% of valgum is normal

Function of the PFJ

Acts as a transmitter of quadriceps force across the knee Protection for the anterior knee

The "Q" angle

Angle between the quad vector (mainly along the rectus femoris) and the patellar tendon.

Anterior Cruciate Ligament (ACL)

Attaches to anterior tibia Prevents forward sliding of tibia

posterior cruciate ligament

Attaches to posterior tibia Prevents backward sliding of tibia

posterior knee muscles

Bicep femoris (long and short heads), popliteus, semimembranosus, semitendinosus, sartorius, gracilis, gastrocnemius, tensor fascia latae

Which muscle of the hamstring group does not cross the hip?

Bicep femoris short head

Sciatic Nerve-Peroneal (weird one)

Biceps femoris short head

Menisci of the knee - medial side is

C shaped

patellar chondromalacia

Caused by trauma or overuse of the knee leading to improper kneecap movement.

Function of the Patellofemoral Joint

Enhancing the leverage (internal moment arm) of the quadriceps muscle

Some effects on weight=bearing surfaces of the knee when the line of gravity does not fall in the normal position through the knee joint because of

Excessive genu-valgum/knock-knee Excessive genu-varum/bow-leg Recurvatum/knee hyperextension

laceration or other damage to this one nerve can result in complete paralysis of the knee extensor muscles.

Femoral nerve, sole source of innervation to the quadriceps

Proximal Fibula

Fibular head Proximal tibiofibular joint

Tibial nerve

Gastrocnemius Popliteus Plantaris

Sciatic nerve - tibial portion

Hamstrings: Semitendinosus Semimembranosus Biceps femoris - long head

Hamstring group actively insufficient

Hip - extended Knee - flexed Hamstrings

Rectus femoris passively insufficient

Hip - extended Knee - flexed Rectus femoris

Rectus femoris actively insufficient

Hip - flexion Knee - extension Rectus femoris

Hamstring group passively insufficient

Hip - flexion Knee - extension Hamstrings

Intrinsic Factors

Imbalance of forces between the vastus medialis obliquus (VMO) and the vastus lateralis Tight IT band or lateral patellar retinaculum Decreased slope of the lateral facet on the intercondylar groove of the femur

extensor lag

Inability to extend the knee the last 15° Because the VM was seen to atrophy most, it was thought to be the terminal knee extensor EMG later showed that all the quads were simply too weak to lift the lower leg, and the Vastus Medialis is simply the most superficial Swelling makes it worse

Does the area of contact on the patella increase or decrease? (as it moves proximally, as the knee flexes toward 90⁰)

Increases

What does bursae of the knee do?

It reduces friction

Consequences of Tight Hamstrings

Knee flexion contracture Posterior pelvic tilt Can't touch toes, can't sit, can't go upstairs

Patella - Is the lateral facet larger or smaller than the medial facet. Both are concave.

Larger (L for later and larger)

The popliteus muscle has its proximal attachment on which side of the posterior knee?

Lateral

Distal Femur

Medial and lateral condyles Intercondylar groove (trochlea) Medial and lateral epicondyles

Proximal Tibia

Medial and lateral condyles (plateaus) Intercondylar eminence Tibial tubercle (tuberosity)

The patella is capable of three dimensional motion with translation along and rotation about the cardinal axes

Medial-lateral tilt Flexion-extension Patellar-rotation

Menisci of the knee - lateral side is

O shaped

Posterior Capsule

Prevents hyperextension (no body block like elbow) Two ligaments: Arcuate popliteal Oblique popliteal Marked hyperextension: Genu recurvatum

Starting at the tibial tuberosity and proceeding laterally around the knee, name, in order, the muscles that span the knee joint

Quadriceps TFL tensor fascia late ITB iliotibial band Bicep femoris Gastrocnemius popliteus Gastrocnemius Semitendinosus Semimembranosus Gracilis Sartorius

Articulation of the Femur/Tibia and Superior Tibia/ Fibula and the Patella/Femur.

ROM: Saggital plane motion on a frontal plane axis Flexion 0-140 Extension 0 Small amount of external rotation of tibia during late extension (not measured) Open packed position is 25 degrees of flexion

Which muscle of the quadriceps group crosses the hip?

Rectus femoris

Two joint muscles of the knee

Rectus femoris Biceps femoris (long head) Semimembranosus Semitendinosus Sartorius Gracilis Gastrocnemius Tensor fascia latae

The femoral condyles act as simple pulleys for the tendons of which 3 muscles?

Sartorius Gracilis Quadriceps

What 3 muscles attach to the pes anserine and create boundaries

Sartorius Gracilis Semitendinosus SGT muscles

What knee flexor is innervated by the fibularis nerve?

Short head of bicep femoris located on the lateral side of the posterior knee

The "Terrible Triad"

Simultaneous injury to the ACL, MCL, and medial meniscus Most often occurs as a result of a large rotational and valgus force to the nearly fully extended knee, when the foot is firmly planted on the ground

Patella

Superior Pole (base) Inferior Pole (apex) Medial facet Lateral facet

concave-convex rule

The distal femur is convex, its articulates on the tibia which is concave (due to meniscus). Take the bone which is moving, in this case its the tibia. It is conCAVE, which means its surface will slide in the SAME direction as the bone's movement.

A more effective stretch of the rectus femoris.

The pelvis is well stabilized by the rectus abdominis as the hip is extended

One joint muscle of the knee

Vastus lateralis, vastus medialis, vastus intermedius, bicep femoris (short head), popliteus

WHY IS THE Q ANGLE LARGER IN WOMEN THAN IN MEN?

WOMEN GENERALLY HAVE A LARGER PELVIS Women < 22°, Men < 18°

closed chain, femoral on tibial perspective

most common

Injury and Healing of Menisci - Middle third poor blood supply

poor blood supply

What artery and vein pass through the popliteal fossa

popliteal artery and vein

Femoral nerve

rectus femoris vastus medialis vastus lateralis vastus intermedius sartorius

Muscles that attach distal to knee and proximal on the pelvis. Anteriorly and moving medially around the knee

rectus femoris sartorius gracilis semitendinosus semimembranosus bicep femoris

anterior knee muscles

rectus femoris, vastus lateralis, vastus intermedius, vastus medialis

Muscle that makes up the superior medial border of the popliteal fossa

semimembranosus

The vein that enters the fossa inferiorly to join the vein is the

small saphenous vein

The Q-angle indicates

the relative lateral force that is applied to the patella during a quadriceps contraction.

concave-convex (same)

tibia moves on femur

The popliteus muscle is innervated by the

tibial nerve

What nerve passes through the MIDDLE of the popliteal fossa

tibial nerve

quadriceps, knee extensor muscles; rectus femoris, vastus lateralis, vastus medialis, and vastus intermedius. All 4muscles originate from a different area of the femur or pelvis, they join together and attach distally—as a group—tendon.

to the tibial tuberosity via the patellar

The patella is in what groove

trochlear groove

The muscle that forms the floor of the popliteal fossa is the popliteus muscle. True or false

true

Injury and Healing of Menisci - Inner third

avascular

bursae - gastrocnemius is located

between lateral head of gastrocnemius muscle and capsule

bursae - subcutaneous infrapatellar is located

between patella and skin

bursae - deep infrapatellar is located

between proximal tibia and patellar ligament

Frontal plane deviations (hip and knee)

valgum <165 varum > 180

Muscle that makes up the superior lateral border of the popliteal fossa

bicep femors

There is less patellofemoral compression

when in extension

There is more patellofemoral compression

when in flexion

70% of load is taken by mensici yes or no

yes

In closed chain there is not much patellofemoral compression. yes or no

yes

What nerve passes through the popliteal fossa on the LATERAL border

common fibular nerve

bursae - fibular collateral ligament is located

deep to fibular collateral ligament and next to the bone

Convex-concave (opposite)

femoral moves on tibia

The area of contact on the patella increases and moves proximally as the knee

flexes toward 90

ACL (name by tibia)

from anterior tibia to posterior femur

PCL (name by tibia)

from posterior tibia to anterior femur

multijoint muscle that crosses the knee and attaches posteriorly on the calcaneus

gastrocnemius

Muscles that make up the inferior medial and lateral border of the popliteal fossa are

gastrocnemius and plantaris

Injury and Healing of Menisci - Outer third good blood supply

good blood supply

Obturator nerve

gracilis

Muscular boundaries - diamond shape

has inside tibial nerve and common fibular and blood vessels Superior/medial: semitendinouse and membransous Lateral= bicep femors Inferior: medial and lateral gastroc

Main role of PFJ (patellar femoral joint) is to

increase the mechanical advantage of the quads and protect the knee joint