Knee joints

XY2141: Anatomy - Knee Joint, Leg Region

• Course lecturer: Dr. Viktoriia Yerokhina
• Email: [email protected]

Learning Outcomes

• ANAT.35.01: Discuss the anatomy of the knee joint (bones, ligaments, blood supply, actions).
• ANAT.35.02: Identify the bones and features of the leg (tibia and fibula).
• ANAT.35.03: Review the compartments of the leg, the muscles within each compartment, and describe their functions. Identify the muscles in each compartment.
• ANAT.35.04: Summarize the neurovascular structures (arteries, veins, nerves) of the leg. Include the common peroneal nerve to fibula, popliteal artery to femur, tarsal tunnel and their clinical importance.
• ANAT.35.05: Discuss the relationship of structures related to bone (e.g. common peroneal nerve to fibula).
• ANAT.35.06: Apply anatomical knowledge to clinical correlations of the leg region.
• Tarsal tunnel will be mentioned in the next lecture (Ankle, Foot).

Patella

• Sesamoid bone in the tendon of the quadriceps femoris. Part of the knee joint.
• 1. Base: wide proximal part.
• 2. Apex: pointy distal end.
• 3. Articular surface: dorsal surface, divided into lateral and medial facets.
• 4. Anterior surface: roughened ventral surface. Includes part of the quadriceps femoris tendon.

Tibia (Shinbone)

• Weight-bearing, long bone of the leg, located medially.
• Distal end: forms the medial malleolus.
• Anterior margin and medial surface: not covered by muscles, therefore palpable.
• 1. Condyles: widened proximal end, has medial and lateral condyles.
  • 1.1 Superior articular surface: for articulation with the femoral condyles.
  • 1.2 Intercondylar eminence: located in the middle of the superior articular surface and comprises the medial and lateral tubercle.
• 1.3 Anterior intercondylar area: attachment point for the anterior cruciate ligament and menisci.
• 1.4 Posterior intercondylar area: attachment point for the posterior cruciate ligament and menisci.
• 1.5 Fibular articular facet: articulates with the head of the fibula.
• 2. Shaft (corpus tibiae): body of the tibia.
  • 2.1 Soleal line: origin of the soleus muscle.
  • 2.2 Tibial tuberosity: insertion of the quadriceps femoris (as the patellar ligament).
• 2.3 Medial surface: palpable as it's not covered in muscles.
• 2.4 Lateral surface.
• 2.5 Posterior surface.
• 2.6 Anterior border: palpable as it's not covered in muscles
• 2.7 Interosseous border: attachment of the interosseous membrane of the leg.
• 2.8 Medial border.
• 3. Distal end:
  • 3.1 Medial malleolus: medial side of the ankle.
  • 3.1.1 Malleolar groove: forms the malleolar canal with the flexor retinaculum.
  • 3.1.2 Articular facet: articulates with the talus.
  • 3.2 Fibular notch: part of the tibiofibular syndesmosis.
  • 3.3 Inferior articular surface: articulates with trochlea of the talus.

Fibula (Calfbone)

• A long bone on the lateral aspect of the leg.
• Does not bear body weight, only for muscle attachments.
• Distal end: forms the lateral malleolus.
• 1. Head (caput fibulae): insertion of the biceps femoris. Attachment of the fibular collateral, arcuate popliteal ligaments, anterior and posterior ligaments. Origin of soleus and fibularis longus.
  • 1.1 Apex: of head .
  • 1.2 Articular facet: articulates with the tibia.
• 2. Neck (collum fibulae): common fibular nerve runs around the neck.
• 3. Shaft (corpus fibulae):
  • 3.1 Lateral surface
  • 3.2 Medial surface
  • 3.3 Posterior surface
  • 3.4 Anterior border
  • 3.5 Posterior border
  • 3.6 Interosseous border
  • 3.7 Medial crest
• 4. Lateral malleolus (malleolus lateralis):
  • 4.1 Articular facet: articulates with the talus.
  • 4.2 Malleolar fossa:
  • 4.3 Malleolar groove

Knee Joint (Articulatio Genus)

• Most complex synovial joint.
• Three bones and two menisci articulate.
• 12 articular ligaments and associated bursae.
• Movements are limited in full flexion and extension.

Knee Joint (Type, Shape, and Articular Surfaces)

• Type: Complex and compound bicondylar.
• Femoropatellar joint:
  • Shape: Plane.
  • Articular head: Patellar surface of femur.
  • Articular fossa: Articular surface of patella.
• Femorotibial joint:
  • Shape: Combination of hinge and pivot joints.
  • Articular head: Condyles of femur.
  • Articular fossa: Condyles of tibia.

Knee Joint (Three Primitive Joints)

• Medial and lateral femorotibial joints.
• Patellofemoral joint.

Knee Joint (Radiograph)

• AP view.
• Lateral view.
• Sky view.

Knee Joint (Articular Capsule)

• Fibrous capsule (originates beneath epicondyles of the femur, attaches to the circumference of the articular surfaces of the tibia and patella).
• Synovial membrane (lines the internal surface of the fibrous layer; does not cover cruciate ligaments).
  • 2.1 Infrapatellar synovial fold: projects dorsally from the ventral part of the joint.
  • 2.2 Infrapatellar fat pad: fat pad between the fibrous and synovial layers.

Knee Joint (Synovial Bursae and Articular Recesses)

• Approximately 20 bursae and 2 recesses located near or communicating with the knee joint.
• Not communicating: Subcutaneous prepatellar bursa; Subcutaneous infrapatellar bursa

Ligaments

• Collateral ligaments:
  • Tibial (medial): Runs from medial epicondyle of femur to tibia. Attaches firmly to medial meniscus.
  • Fibular (lateral): Runs from lateral epicondyle of femur to head of fibula.
• Ventral ligaments:
  • Medial and lateral patellar retinacula: Hold patella in the shallow patellar surface of the femur.
  • Patellar ligament: Insertion of quadriceps femoris between the patella and tibial tuberosity.
• Dorsal ligaments:
  • Oblique popliteal ligament: One of the insertions of semimembranosus.
  • Arcuate popliteal ligament: Forms an arch above the tendon of the popliteus.
• Intra-articular ligaments:
  • Anterior cruciate ligament (ACL): Runs from medial surface of lateral condyle of femur to anterior intercondylar area of tibia.
  • Posterior cruciate ligament (PCL): Runs from lateral surface of medial condyle of femur to posterior intercondylar area of tibia.
  • Transverse ligament: Connects both menisci ventrally.
  • Meniscofemoral ligaments: Weak ligaments around the posterior cruciate ligament.

Menisci

• Medial meniscus: C-shaped
• Lateral meniscus: O-shaped.
• Both attach to the anterior and posterior intercondylar areas.
• Medial meniscus is firmly attached to the capsule and laterally to the tibial collateral ligament; limits its mobility, more mobile than medial. 

Movements

• Flexion: 0-150°.
• Extension: 0°.
• Rotations: Possible only in flexed knees.
  • Internal rotation: 5-10°.
  • External rotation: Approximately 40°.

Common Knee Injuries

• Torn ACL (anterior cruciate ligament)
• Torn medial meniscus
• Torn MCL (medial collateral ligament)

Unhappy Triad (O'Donoghue Triad)

• Simultaneous injury of tibial (medial) collateral ligament, anterior cruciate ligament, and medial meniscus

Genu Varum and Genu Valgum

• Genu valgum: (knocked knees) lateral misalignment of the knee.
• Genu varum: (bowlegged) medial misalignment of the knee.

Popliteal Artery

• Direct continuation of the femoral artery.
• Runs in the popliteal fossa with the popliteal vein. Runs laterally and posteriorly.
• Upon reaching the leg, it enters the cruropopliteal canal, giving off anterior and posterior tibial arteries.
• Also gives off five genicular arteries.

Nerve Supply of the Knee Joint

• Innervation from the femoral nerve (via saphenous nerve and muscular branches).
• Also receives contributions from the tibial and common fibular (peroneal) nerves, and the posterior division of the obturator nerve.

Muscles of the Leg

• Anterior Group:
  • Tibialis anterior
  • Extensor digitorum longus
  • Extensor hallucis longus
• Lateral Group:
  • Fibularis longus
  • Fibularis brevis
• Posterior Group - Superficial Layer:
  • Triceps surae (soleus and gastrocnemius)
  • Plantaris
• Posterior Group - Deep Layer:
  • Popliteus
  • Tibialis posterior
  • Flexor digitorum longus
  • Flexor hallucis longus

Tendocalcaneus (Achilles Tendon)

• Conjoint tendon of insertion of gastrocnemius and soleus (triceps surae).
• Thickest and strongest tendon (about 15 cm long).
• Prime mover of plantar flexion of the foot at the ankle joint.

Ancient Greek Mythological Figure Achilles

• Achilles tendon is named after the mythological figure Achilles. His mother held him by the heel during a dipping ritual in the River Styx to make him invulnerable. 

Clinical Correlation - Achilles Tendon Ruptures

• Primary in men aged 30-50.
• Often from indirect trauma, related to sports or exercise.
• Pre-existing disorders and some medication linked to increased risk.
• Often sharp pain in the back of the ankle with a popping sensation.
• Treatment recommendations are conservative and surgical approaches.

Muscles of the Leg (Posterior Group – Deep Layer)

• Popliteus
• Tibialis posterior
• Flexor digitorum longus
• Flexor hallucis longus

Blood Supply of the Leg

• Popliteal artery (direct continuation of the femoral artery, supplies the lower limb).
  • Splits into anterior and posterior tibial arteries.
• Anterior tibial artery (main blood supply for the anterior compartment of the leg).
• Posterior tibial artery (supplies the posterior and lateral sides of the calf, sole, and lateral muscles).

Veins of the Leg

• Deep veins: Located underneath the deep fascia, accompanying the major arteries.
• Superficial veins: Found in subcutaneous tissue, eventually drain into the deep veins.
  • Long (great) saphenous vein
  • Short (small) saphenous vein
• Anterior tibial vein
• Posterior tibial vein
• Fibular (peroneal) veins

Clinical Correlation - Chronic Venous Disease/Disorders

• Spectrum of disorders caused by venous dysfunction, ranging from telangiectasia to venous ulceration.
• Chronic venous insufficiency (CVI): advanced form of CVD.
• Varicose veins: type of CVD characterized by dilated superficial veins (diameter > 3 mm) and tortuousity.

Nerves of the Leg

• Sciatic nerve: Terminates at the apex of the popliteal fossa, dividing into tibial and common peroneal nerves.
• Cutaneous branch: From both the tibial and common peroneal nerves unite to form the sural nerve.

Clinical Correlation- Nerve Injuries

• Tibial nerve injury (TIIPPED): Inability to walk on tip toes; inverts and plantarflexes foot.
• Peroneal nerve injury (PED): Foot drop; everts and dorsiflexes foot.

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