Knee and Lower Leg

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)

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

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

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

• The knee joint is the largest joint in the body

• The knee joint is a ginglymus (hinge) joint that allows rolling and sliding

• Static restraints

  • Ligaments

    • ACL—resists anterior translation

    • PCL—resists posterior translation

    • MCL—resists valgus displacement

    • LCL—resists varus displacement

    • Popliteus tendon—resists external rotation

    • Posteromedial and posterolateral capsular structures—resist rotation

  • Menisci

    • Medial—semicircular and broader posteriorly

    • Lateral—more circular and covers a larger portion of the articular surface

  • Articular congruity

• Dynamic restraints

  • Quadriceps muscles

  • Hamstring muscles

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

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)

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

• Sciatic nerve—divides in midthigh

  • Tibial division

  • Peroneal division

• Femoral nerve

• Obturator nerve

Femoral Artery

• Thigh branches

• Trifurcation

  • Anterior tibial artery

  • Posterior tibial artery

  • Peroneal artery (usually splits from the posterior branch)

Anterior Compartment

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

• Superficial femoral artery and vein

• Saphenous nerve

Medial Compartment

• Adductor longus, adductor brevis, adductor magnus, and gracilis

• Deep femoral artery and vein

Posterior Compartment

• Biceps femoris, semitendinosus, and semimembranosus

• Sciatic nerve

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

• Tibial nerve

• Posterior tibial artery and vein

Sciatic Nerve

• The main nerve to the lower extremity

• At risk

  • Dissection near ischium (proximal hamstring injuries)

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

• At risk

  • Popliteal dissection

  • PCL inlay reconstructions

  • PCL bony avulsion repairs

Vascular