Knee and Lower Leg

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Chapter 7

Knee and Lower Leg

Robert F. LaPrade, Nicholas I. Kennedy

Regional Anatomy

Osteology

Distal Femur (Fig. 7-1)

The femur (the largest bone in the body) flares distally and forms two condyles—a larger medial condyle and a longer and more narrow lateral femoral condyle

The intercondylar area serves as the region for cruciate attachments—the lateral, anterior cruciate ligament (ACL) and the medial, posterior cruciate ligament (PCL)

The superficial medial collateral ligament (MCL) attaches adjacent to the medial epicondyle

The medial patellofemoral ligament inserts just distal to the adductor tubercle, and the adductor magnus tendon inserts on the adductor tubercle at the superior aspect of the medial epicondyle; in addition, the posterior oblique ligament attaches adjacent to the gastrocnemius tubercle

The attachment of the lateral collateral ligament (LCL) is adjacent to the lateral epicondyle; it is less prominent than the medial epicondyle

The popliteus tendon lies in a groove distal to the lateral epicondyle and within the popliteal hiatus (at its proximal fifth)

FIGURE 7-1 Bony architecture of the distal femur.

Proximal Tibia (Fig. 7-2)

The tibia is the second longest bone in the body

The plateau areas match the corresponding femoral condyle

• The medial tibial plateau is broad and concave

• The lateral tibial plateau is smaller and convex

The tibial eminences (spines) define the borders of the cruciate ligament insertions

• The ACL lies between the eminences

• The PCL lies within the PCL facet, adjacent to the posterior aspects of the medial and lateral tibial plateaus; in addition, its distal fibers attach at the posterior tibial drop-off, which radiographically is known as the “champagne glass drop-off” of the tibia

The tubercles serve as attachments for tendons

• The tibial tubercle (or tuberosity) serves as the patellar tendon attachment

• Gerdy’s tubercle serves as the iliotibial band attachment

FIGURE 7-2 Bony architecture of the proximal tibia. PCL, Posterior cruciate ligament.

Patella (Fig. 7-3)

The patella is the largest sesamoid bone in the body

It has the thickest articular cartilage in the body

Medial and lateral facets

• The lateral facet is larger

• The facets are separated by a vertical ridge

FIGURE 7-3 Bony architecture of the patella.

Arthrology

Knee Joint (Figs. 7-4 and 7-5)

FIGURE 7-4 Knee (femorotibial) joint.

FIGURE 7-5 Knee joint (hinged open).

Proximal Tibiofibular Joint

Plane gliding joint

Surrounded by a thick capsule

Anterior and posterior ligaments of the head of the fibula stabilize the joint

Patellofemoral Joint

A plane (gliding) joint that stabilizes the patella in the trochlear groove of the femur and enhances the effect of the quadriceps muscles (fulcrum effect)

Medial patellofemoral ligament—the primary restraint to lateral patellar displacement

Capsule/retinaculum

Muscles

Knee and leg muscles are best considered in groups or compartments (Figs. 7-6 and 7-7; Tables 7-1 and 7-2)

FIGURE 7-6 Muscles (anterior and lateral views).

FIGURE 7-7 Muscles (posterior view).

Table 7-1

Muscles of the Thigh

MUSCLE	ORIGIN	INSERTION	INNERVATION
Vastus lateralis	Iliotibial line/greater trochanter/lateral linea aspera	Lateral patella	Femoral
Vastus medialis	Iliotibial line/medial linea aspera/supracondylar line	Medial patella	Femoral
Vastus intermedius	Proximal anterior femoral shaft	Patella	Femoral
Biceps (long head)	Medial ischial tuberosity	Fibular head/lateral tibia	Tibial
Biceps (short head)	Lateral linea aspera/lateral intermuscular septum	Fibular styloid/posterolateral joint capsule	Peroneal
Semitendinosus	Distal medial ischial tuberosity	Anterior tibial crest	Tibial
Semimembranosus	Proximal lateral ischial tuberosity	Oblique popliteal ligament	Tibial
		Posterior capsule
		Posterior/medial tibia
		Fabella/lateral gastrocnemius tendon
		Medial meniscus

Table 7-2

Muscles of the Leg

MUSCLE	ORIGIN	INSERTION	ACTION	INNERVATION
Anterior Compartment
Tibialis anterior	Lateral tibia	Medial cuneiform, first metatarsal	Dorsiflex, invert foot	Deep peroneal (L4)
Extensor hallucis longus	Mid fibula	Great toe distal phalanx	Dorsiflex, extend toe	Deep peroneal (L5)
Extensor digitorum longus	Tibial plateau/fibula	Toe middle and distal phalanges	Dorsiflex, extend toes	Deep peroneal (L5)
Peroneus tertius	Fibula and extensor digitorum longus tendon	Fifth metatarsal	Evert, plantar flex, abduct foot	Deep peroneal (S1)
Lateral Compartment
Peroneus longus	Proximal fibula	Medial cuneiform, first metatarsal	Evert, plantar flex, abduct foot	Superficial peroneal (S1)
Peroneus brevis	Distal fibula	Tuberosity of fifth metatarsal	Evert foot	Superficial peroneal (S1)
Superficial Posterior Compartment
Gastrocnemius	Posterior, medial, and lateral femoral condyles	Calcaneus	Plantar flex foot	Tibial (S1)
Soleus	Fibula/tibia	Calcaneus	Plantar flex foot	Tibial (S1)
Plantaris	Lateral femoral condyle	Calcaneus	Plantar flex foot	Tibial (S1)
Deep Posterior Compartment
Popliteus	Lateral femoral condyle, fibular head	Proximal tibia	Flex, internal rotation knee	Tibial (L5, S1)
Flexor hallucis longus	Fibula	Great toe distal phalanx	Plantar flex great toe	Tibial (S1)
Flexor digitorum longus	Tibia	Second-fifth toe distal phalanges	Plantar flex toes, foot	Tibial (S1, S2)
Tibialis posterior	Tibia, fibula, interosseous membrane	Navicular, medial cuneiform	Invert/plantar flex foot	Tibial (L4, L5)

Anterior Thigh

Quadriceps muscles

• Vastus lateralis, intermedius, and medialis and rectus femoris

Posterior Thigh

Hamstring muscles

• Lateral—biceps femoris (long and short heads)

• Medial—semimembranosus, semitendinosus, sartorius, and gracilis

Adductors—magnus, longus, and brevis

Anterior Leg

Tibialis anterior, extensor hallucis longus, and extensor digitorum longus

Posterior Leg

Gastrocnemius, soleus, plantaris, flexor hallucis longus, flexor digitorum longus, tibialis posterior (deep), and popliteus

Lateral Leg

Peroneus brevis, longus, and tertius (distally)

Nerves

Extension of Nerves from the Lumbosacral Plexus (Fig. 7-8)

Sciatic nerve—divides in midthigh

• Tibial division

• Peroneal division

Obturator nerve

FIGURE 7-8 Major nerves of the thigh and leg.

Vascularity (Fig. 7-9)

Femoral Artery

• Anterior tibial artery

• Posterior tibial artery

• Peroneal artery (usually splits from the posterior branch)

FIGURE 7-9 Major arteries of the thigh and leg.

Cross-Sectional Anatomy (Fig. 7-10)

Thigh

Anterior Compartment

Vastus medialis, vastus intermedius, vastus lateralis, rectus femoris, and sartorius

Superficial femoral artery and vein

Saphenous nerve

FIGURE 7-10 Cross section of the thigh and lower leg.

Medial Compartment

Adductor longus, adductor brevis, adductor magnus, and gracilis

Deep femoral artery and vein

Posterior Compartment

Biceps femoris, semitendinosus, and semimembranosus

Lower Leg

Anterior Compartment

Tibialis anterior, extensor hallucis longus, and extensor digitorum longus

Deep peroneal nerve

Anterior tibial artery and vein

Lateral Compartment

Peroneus longus and brevis

Superficial peroneal nerve

Superficial Posterior Compartment

Gastrocnemius, soleus, and plantaris

Deep Posterior Compartment

Flexor hallucis longus, flexor digitorum longus, and tibialis posterior

Posterior tibial artery and vein

Superficial Landmarks

FIGURE 7-11 Superficial landmarks.

Radiologic Landmarks

(Figs. 7-12 through 7-15)

FIGURE 7-12 Radiologic landmarks of the knee. PCL, Posterior cruciate ligament.

FIGURE 7-13 Radiologic landmarks of the knee.

FIGURE 7-14 Radiologic landmarks of the knee. ACL, Anterior cruciate ligament; MCL, medial collateral ligament.

FIGURE 7-15 Radiologic landmarks of the knee.

Hazards (Fig. 7-16)

Sciatic Nerve

The main nerve to the lower extremity

• Dissection near ischium (proximal hamstring injuries)

FIGURE 7-16 Hazards in the posterior thigh and leg.

Peroneal Nerve

A branch of the sciatic nerve that crosses the fibula before dividing into superficial and deep branches

At risk—peroneal nerve

• As it crosses the neck of the fibula

• Posterolateral lance surgical approaches

• Biceps femoris avulsions

• LCL reconstructions

• Lateral meniscus repairs

At risk—superficial peroneal nerve

• During lower extremity compartment release, approximately 12 cm proximal to the tip of the lateral malleolus

Tibial Nerve

• Popliteal dissection

• PCL inlay reconstructions

• PCL bony avulsion repairs

Vascular

Popliteal Artery and Vein

• Popliteal dissection and PCL transtibial procedure

• Knee arthroplasty, especially in revision cases where bone loss extends posteriorly

• Meniscal root repairs and meniscal transplantations

Geniculate Arteries

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