Knee - Anatomy & Biomechanics

Question 1

Three joints of the knee = ?

Knee - Anatomy & Biomechanics

Answer 1

Joints of the Knee:

(1) Tibiofemoral Joint:

• Between the femur of the thigh and the tibia of the shank.

(2) Patellofemoral Joint:

• Between the aforementioned femur and the largest sesamoid bone in our body – the patella.

(3) Proximal Tibiofibular Joint:

• This bony attachment is instead built for stability, anchoring the fibula for muscle attachment.
• Distal & lateral two the two previously mentioned primary joints.

Question 2

Tibiofemoral Joint

• Primary weight-bearing joint, that guides = ?

1st & 2nd

Knee - Anatomy & Biomechanics

Answer 2

Tibiofemoral Joint:

- Primary weight-bearing joint, that
guides

• 1st = Flexion/Extension
• 2nd = Int/Ext Rot

- Frontal Plane:

• Medial Condyle: Our primary weight bearing structure in the knee. It’s closer to our center of gravity, necessitating less medial/lateral translation of our COM to bear weight, so a more distal medial side biases this compartment to accept more load.
• More Distal
• Accepts Center of Gravity During Stance Phase

- Sagittal Plane:

• Longer by ½ in.
• Drives the Screw-Home Mechanism: About 80% of this coupling happens within the terminal 30d of knee extension, so this is primarily a “leg-straight” event.
• Tibial Plateau Declination

- Transverse Plane:

• Lateral Plateau
• Closer to Convex on Convex
• Lateral Tibial Plateau Smaller than Medial

Question 3

Knee - Anatomy & Biomechanics

Question 4

Knee - Anatomy & Biomechanics

Question 5

Patellofemoral Joint Articulation

Tracking Pathway:

• Begins slightly _ ? _ to the femoral sulcus
• Lateral Contact guides the _ ? _
• Tracking forms a subtle _ ? _

Knee - Anatomy & Biomechanics

Answer 5

Patellofemoral Joint Articulation:

- Improves Mechanical Advantage of Quads (0-30)

- Tracking Pathway:

• Begins slightly proximal to the Femoral Sulcus
• Lateral Contact guides the Patellar to Full Contact at 30°
• Tracking forms a subtle C Pattern Lat/Med/Lat

Question 6

Patellofemoral Joint Articulation

Tracking Forces:

• Walking = ? x BW
• Jogging = ? x BW
• Deep Squat = ? x BW

Knee - Anatomy & Biomechanics

Answer 6

Patellofemoral Joint Articulation:

- Tracking Forces:

• ½ BW Walking
• 7x BW Jogging
• 20x BW Deep Squat

- Improves Mechanical Advantage of Quads (0-30)

Question 7

Patellofemoral Joint Articulation

Tracking Depends on = ?

Knee - Anatomy & Biomechanics

Answer 7

Patellofemoral Joint Articulation:

- Tracking Depends on:

• Bony architecture of femoral Sulcus/Patella
• Extensibility of the surrounding connective tissue
• Quadriceps Activation

- Improves Mechanical Advantage of Quads (0-30)

Question 8

Patellofemoral Joint Movements

Movements include = ?

Knee - Anatomy & Biomechanics

Answer 8

Patellofemoral Joint Movements:

- Movements:

• Superior (Extension)/Inferior (Flexion) Glide
• Medial/Lateral Glide
• Medial/Lateral Tilt
• Medial/Lateral Rotation

Question 9

Tibiofibular Joint

• Is WB or NWB = ?
• Situated _ ? _ to the Tibia
• _? _ nerve wraps around the Fibular Head

Knee - Anatomy & Biomechanics

Answer 9

Tibiofibular Joint:

- Non-Weight-bearing Joint:

• 3mm of Movement
• Functionally part of the Ankle

- Situated Posterior to the Tibia:

• Solution = 45° Anterior-Lateral/Posterior-Medial

- Fibular Nerve:

• Wraps around the Fibular Head

Question 10

Anterior Cruciate Ligament

Dynamic Stability of the Knee:

• Load is highest in = ?
• Taut throughout = ?

Knee - Anatomy & Biomechanics

Answer 10

Anterior Cruciate Ligament:

- Dynamic Stability of the Knee:

• Load is highest In extension (Inverse of PCL)
• Taut throughout entire range

Question 11

Anterior Cruciate Ligament

• ACL has ? distinct bundles

Describe them

Knee - Anatomy & Biomechanics

Answer 11

Anterior Cruciate Ligament:

- Two distinct Bundles: Named for where they attach on the tibia.

(1) Posterior-lateral: Extension, Thicker (Parallel)

• The larger of the two, the posterior lateral bundle accepts this force in an extended knee with both bundles running parallel.

(2) Anterior-medial: Flexion (Crossed)

• The anterior-medial bundle crosses over the other to accept more force as the knee moves into flexion.

Question 12

Anterior Cruciate Ligament

• Primary Role = ?
• Secondary Role = ?

Knee - Anatomy & Biomechanics

Answer 12

Anterior Cruciate Ligament:

- Primary Role:

• Prevent anterior tibial translation
• 75% of Anterior Translation at 0°
• 85% at 30°

- Secondary Role:

• Secondary stabilizer of tibial rotation (IR>ER)
• Tertiary stabilizer of tibial external rotation (IR>ER)
• 30° most IR from ACL
• 20-50° most unstable 2nd to laxity from ACL/PCL

Question 13

ACL and PCL have their greatest slack between = ?

Knee - Anatomy & Biomechanics

Answer 13

ACL and PCL have their greatest slack between 20 and 50d.

Question 14

Anterior Cruciate Ligament

Explain the importance of the “Twisted Fiber” / Double helix orientation of the ACL = ?

Knee - Anatomy & Biomechanics

Answer 14

Anterior Cruciate Ligament:

- Stores Energy:

(a) Twisted Fibers:

• Allow diffuse insertions and compact midsection.
• 90° Helix Stores Energy During Loading
• - The helixed nature of these fibers store energy in flexion that is released into extension moments.

(b) Change of Fiber Orientation

• Origin Vertical
• Insertion Horizontal

- Vascularization:

• Middle Genicular Artery

Question 15

Anterior Cruciate Ligament

• Is innervated by the ? nerve.
• Innervation of this structure is largely ? in nature.

Knee - Anatomy & Biomechanics

Answer 15

Anterior Cruciate Ligament:

- Tibial Innervation

(a) Innervation of this structure is largely proprioception in nature.

• Reflexively activates the hamstrings and quads
• Minimal pain fibers

Question 16

Anterior Cruciate Ligament

Vascularization from the ? provides ample blood flow, which is all well and good, but it does lead to ? if the ACL is ever torn.

Knee - Anatomy & Biomechanics

Answer 16

Anterior Cruciate Ligament:

- Vascularization from the middle genicular artery provides ample blood flow, which is all well and good, but it does lead to significant swelling if the ACL is ever torn.

- Vascularization: Middle Genicular Artery.

Question 17

Posterior Cruciate Ligament

• Originating off the _ ? _ , this ligament is _ ? _ than its ACL counterpart.

Knee - Anatomy & Biomechanics

Answer 17

Posterior Cruciate Ligament:

- Originating off the medial femoral condyle, this ligament is 20% bigger than its ACL counterpart and more isometric/less extensible when the knee moves.

• Load is Highest In Flexion (Inverse of ACL)

- Works with other structures to stabilize posterior translation

• Popliteus
• Meniscofemoral Ligaments

Question 18

Posterior Cruciate Ligament

The PCL is loaded most when in _ ? _ and it’s primary job is to resist _ ? _ , especially when the knee is between ? _ d of flexion.
## Footnote

Knee - Anatomy & Biomechanics

Answer 18

Posterior Cruciate Ligament:

• PCL is loaded most when in flexion and it’s primary job is to resist posterior tibial translation, especially when the knee is between 70-90 d of flexion.

- Primary Role = Resist Posterior Tibial Translation.

• Most Challenged between 70-90 ° Flexion
• Taut Throughout Entire Range

- Secondary Role = Stabilize tibial external rotation

Question 19

Posterior Cruciate Ligament:

• The Anterolateral bundle taught during = ?
• The Posteromedial bundle is taught during = ?

Knee - Anatomy & Biomechanics

Answer 19

Posterior Cruciate Ligament:

- Two distinct Bundles:

• The thicker Anterolateral bundle taught during flexion.
• The Posteromedial bundle is taught during extension.

Question 20

Posterior Cruciate Ligament:

The PCL works with what other structures to stabilize posterior translation = ?

Knee - Anatomy & Biomechanics

Answer 20

Posterior Cruciate Ligament:

- Works with other structures to stabilize posterior translation

• Popliteus
• Meniscofemoral Ligaments

Question 21

Medial Collateral Ligament

• The MCL has two portions, what are they = ?
• As a unit, what do they work to prevent = ?t

Knee - Anatomy & Biomechanics

Answer 21

Medial Collateral Ligament: Limits valgus forces & movements.

- The superficial and deep MCL work together to limit valgus forces and positions acting upon the knee.

- Notes:

• The MCL is larger than the LCL
• Broader and Longer

- Bolstered by:

• Pes Anserine Muscles and Semimembranosus

- Two Portions

(1) Superficial MCL

• Primary stabilizer of Valgus Stress
• Taut at End-ranges
• Semimembranosus & Posterior Oblique Ligament

(2) Deep MCL

• Stabilizes Valgus and may help to control anterior translation
• Taut in Extension
• Meniscofemoral and Menisotibial ligaments

Question 22

Medial Collateral Ligament

The LCL is bolstered by _ ? _ and _ ? _ , which when active, more than double the tensile strength of the MCL.

Knee - Anatomy & Biomechanics

Answer 22

Medial Collateral Ligament:

- Bolstered by Pes Anserine muscles, and semimembranosus.

Question 23

Medial Collateral Ligament

• The two portions of the MCL = ?
• Taught in = ?
• What are some connections to both = ?

Knee - Anatomy & Biomechanics

Answer 23

Medial Collateral Ligament:

- Two Portions:

(1) Superficial MCL:

• Primary stabilizer of Valgus Stress
• Taut at End-ranges - most so in extension
• Semimembranosus & Posterior Oblique Ligament

(2) Deep MCL:

• Stabilizes Valgus and may help to control anterior translation
• Taut in Extension
• Meniscofemoral and Menisotibial ligaments

Question 24

Medial Collateral Ligament

The superficial MCL, is the primary component of the structure, bolstering the joint against valgus loads, especially at end-ranges, and the most so in ?

Knee - Anatomy & Biomechanics

Answer 24

The superficial MCL, is the primary component of the structure, bolstering the joint against valgus loads, especially at end-ranges, and the most so in extension.

Question 25

# Medial Collateral Ligament This superficial MCL, being about an inch thick, runs from the _ **?** _ and fans out over the _ **?** _ . ## Footnote *Knee - Anatomy & Biomechanics*

Answer 25

* This superficial MCL, being about an inch thick, runs from the ***medial femoral epicondyle*** and fans out over the ***medial tibia***. * It connects to the ***semimembranosus*** via the ***[posterior oblique ligament](https://musculoskeletalkey.com/classification-of-knee-ligament-injuries/)***.

Question 26

# Lateral Collateral Ligament Lateral Collateral Ligament: * Resists _ **?** _ forces = **?** * Bolstered by the _ **?** _ and _ **?** _ ## Footnote *Knee - Anatomy & Biomechanics*

Answer 26

**Lateral Collateral Ligament**: **-** Resists ***Varus Forces*** * Smaller than the MCL **-** Bolstered by the ***Anterolateral Ligament*** (poor mans ACL), which * Controls tibial internal rotation * Controls anterior tibial translation **-** Bolstered by the ***Iliotibial Band*** (Teal) **-** Diffuse Insertion: * Femur * Patella * Tibia (Gerdy’s Tubercle)

Question 27

The LCL runs from the _ **?** _ of the femur, just proximal to the popliteus, all the way down to the _ **?** _ . ## Footnote *Knee - Anatomy & Biomechanics*

Answer 27

The LCL runs from the ***lateral epicondyle*** of the femur, just proximal to the popliteus, all the way down to the ***fibular head***.

Question 28

# Lateral Collateral Ligament Integrity of the _ **?** _ is thought to help determine the success of ACL recovery in some patients. ## Footnote *Knee - Anatomy & Biomechanics*

Answer 28

**Lateral Collateral Ligament**: Integrity of the ***anterolateral ligament*** is thought to help determine the success of ACL recovery in some patients.

Question 29

# Lateral Collateral Ligament The ITB is unique in how much it fans its insertion over several structures, casting its retinaculum over the _ **?** _ , _ **?** _ , and of course, _ **?** _ . ## Footnote *Knee - Anatomy & Biomechanics*

Answer 29

**Lateral Collateral Ligament**: **-** LCL, bolstered by the IT band, which has a diffuse Insertion on: * Femur * Patella * Tibia (Gerdy’s Tubercle) **-** The ITB is unique in how much it fans its insertion over several structures, casting its retinaculum over the ***femur***, ***patella***, and of course, ***Gerdy’s tubercle***. * While the LCL might not be damaged as often as the MCL, or frankly as cool of a structure, it still is important for knee stability.

Question 30

# Posterior Knee Think of physiologic holes in the posterior capsule as a release valve for Synovial fluid; _ **?** _ may appear when there is too much swelling. ## Footnote *Knee - Anatomy & Biomechanics*

Answer 30

**Posterior Knee**: **-** Durable Structure = * Thick Posterior Capsule * Oblique Popliteal Ligament (Pink) **-** Release Valve for Synovial Fluid * Physiologic Holes in the Posterior Capsule * ***Baker’s Cyst*** Indicative of too much swelling

Question 31

# Posterior Knee The PCL receives posterior support from of two structures; _ **?** _ and _ **?** _ , which both resist _ **?** _ . ## Footnote *Knee - Anatomy & Biomechanics*

Answer 31

**-** The PCL receives posterior support from of two structures; a thick ***posterior capsule*** and the ***oblique popliteal ligament***, which resist * Both structures resist ***hyperextension***

Question 32

# Posterior Knee Posterior lateral corner support is provided by = **?** | *4* ## Footnote *Knee - Anatomy & Biomechanics*

Answer 32

***Posterior lateral corner*** support is provided by: * Lateral Collateral Ligament (Green) * Popliteus (Red) * Arcuate Ligament (Yellow) * Biceps Femoris

Question 33

# Menisci * Provides = **?** * Which meniscus moves more = **?** ## Footnote *Knee - Anatomy & Biomechanics*

Answer 33

**Menisci**: * Provides ***stability***, ***cushion***, ***nutrition***, and ***proprioception*** to the knee. * ***Lateral*** meniscus moves more than medial Attaches to and Dynamized by: Patello-meniscal Retinaculum aka Quads Semimenbranosis/Biceps Femoris/Popliteus Capsule MCL/Mensicofemoral /Mensicotibial Ligaments Vascularity is Worse in the Middle Outside 10-30% = Vascularized Inside = Synovial Fluid (movement important for healing)

Question 34

# Menisci Attaches to, and dynamized (controlled throughout movement) by a host of structures, which include = **?** ## Footnote *Knee - Anatomy & Biomechanics*

Answer 34

**Menisci**: **-** Attaches to and Dynamized by: * Patello-meniscal Retinaculum aka Quads * Semimenbranosis * Biceps Femoris * Popliteus * Capsule * MCL / Mensicofemoral & Mensicotibial Ligaments

Question 35

# Menisci Vascularity is worse in the _ **?**_ . ## Footnote *Knee - Anatomy & Biomechanics*

Answer 35

**Menisci**: **-** Vascularity is worse in the ***middle*** * Outside 10-30% = ***Vascularized*** * Inside = Synovial Fluid (movement important for healing)

Question 36

# Lower Extremity Roles * Trunk = **?** * Hip = **?** * Knee = **?** * Ankle/Foot = **?** ## Footnote *Knee - Anatomy & Biomechanics*

Answer 36

**Lower Extremity Roles**: * Trunk = **Stability** * Hip = **Force Generation** * Knee = **Force Generation** * Ankle/Foot = **Force Transmission**

Question 37

What muscles crossing the knee joint = **?** ## Footnote *Knee - Anatomy & Biomechanics*

Answer 37

**Muscles Crossing the Knee**: **-** **Lateral** = Iliotibial Band **-** **Anterior** = Quadriceps **-** **Posterior** = Hamstrings, Gastrocnemius **-** **Medial** = Gracilis, Sartorius and Adductor Magnus ( *Doesn’t Cross Joint* )

Question 38

# Muscles Crossing the Knee The stability we do have at this joint comes laterally from the _ **?** _ , anteriorly from the _ **?** _ , posteriorly from the _ **?** _ and _ **?** _ , and medially from the _ **?** _ , and _ **?** _ muscles. ## Footnote *Knee - Anatomy & Biomechanics*

Answer 38

**Muscles Crossing the Knee**: **-** The stability we do have at this joint comes * laterally from the ***IT-band*** , * anteriorly from the ***quads*** , * posteriorly from the ***hamstrings*** and ***gastrocs***, and * medially from the ***adductors*** and ***pes anserine muscles*** .

Question 39

# Innervation of the Knee Posterior knee is innervated by = **?** | alot ## Footnote *Knee - Anatomy & Biomechanics*

Answer 39

Innervation of the Knee - **Posterior**: **-** ***Sciatic Nerve***, Mixed (a) ***Sacral Plexus*** (L4-S4) (b) ***Common Fibular Nerve***, Mixed * ***Superficial Fibular Nerve***, Mixed = Muscles of the Lateral Leg * ***Deep Fibular Nerve***, Mixed = Muscles of the Anterior Leg & Dorsum of Foot (c) ***Tibial Nerve***, Mixed = Muscles of the Posterior Leg & Plantar Foot (d) ***Sural Nerve***, Sensory

Question 40

# Innervation of the Knee The sciatic nerve, arising from the sacral plexus from roots _ **?** _ , it exits the pelvis and runs down the posterior leg nestled safely between its bodyguard, the hamstrings. ## Footnote *Knee - Anatomy & Biomechanics*

Answer 40

The sciatic nerve, arising from the sacral plexus from roots ***L4-S4*** , it exits the pelvis and runs down the posterior leg nestled safely between its bodyguard, the hamstrings.

Question 41

# Innervation of the Knee At the top of the popliteal fossa, the sciatic nerve splits into the _ **?** _ and _ **?** _ nerves. ## Footnote *Knee - Anatomy & Biomechanics*

Answer 41

**-** At the top of the popliteal fossa, the sciatic nerve splits into the (1) **Tibial Nerve**: (2) **Common Fibular Nerve**: * Supplies the lateral portion of the knee as it crosses the joint, and then it travels anteriorly, wrapping vulnerably around the fibular head X to then split into a superficial branch that supplies the lateral muscles of the leg, like the peroneals,

Question 42

# Innervation of the Knee Common fibular nerve further divides into = **?** ## Footnote *Knee - Anatomy & Biomechanics*

Answer 42

**-** **Common Fibular Nerve**: Supplies the lateral portion of the knee as it crosses the joint, and then it travels anteriorly, wrapping vulnerably around the fibular head. (1) **Superficial Fibular Nerve** = Muscles of the lateral leg (2) **Deep Fibular Nerve** = Muscles of the anterior leg & dorsum of foot

Question 43

# Innervation of the Knee Anterior knee is innervated by = **?** ## Footnote *Knee - Anatomy & Biomechanics*

Answer 43

Innervation of the Knee - **Anterior**: (a) ***Femoral***, Mixed * Lumbar Plexus (L2-L4) * Muscles of the Anterior Thigh * Sensation of the Anterior Leg * **-** Anterior Cutaneous, Proximal Sensory * **-** Saphenous Nerve, Distal Sensory (b) ***Obturator***, Mixed * Lumbar Plexus (L2-L4) * Muscles of the Medial Thigh * Sensation of the Medial Thigh (c) ***Lateral Cutaneous***, Sensory * Lumbar Plexus (L2-L3) * Sensation of the Lateral Thigh

Question 44

# Innervation of the Knee **True** or **False**: Anteriorly (knee), we deal with nerves from ***higher*** up the spine at the lumbar plexus. ## Footnote *Knee - Anatomy & Biomechanics*

Answer 44

**True** * Anteriorly (knee), we deal with nerves from ***higher*** up the spine at the lumbar plexus.

Question 45

# Innervation of the Knee The largest nerve of the lumbar plexus is the _ **?** _ . ## Footnote *Knee - Anatomy & Biomechanics*

Answer 45

**-** The largest nerve of the lumbar plexus is the ***femoral nerve***, which descends anteriorly to provide muscular innervation to the anterior thigh, like to the sartorius and quads, while also sending off sensory branches called the anterior cutaneous and saphenous nerves. * These provide anteromedial sensation down the entire leg, with the anterior cutaneous being proximal to the knee, and the saphenous nerve being distal.

Question 46

# Innervation of the Knee On the medial side, the _ **?** _ is another mixed nerve that provides a lot of muscular innervation to all our adductors, and it also provides sensory information from the medial leg. ## Footnote *Knee - Anatomy & Biomechanics*

Answer 46

On the medial side, the ***obturator nerve*** is another mixed nerve that provides a lot of muscular innervation to all our adductors, and it also provides sensory information from the medial leg.