Knee and Lower Leg Joints and Ligaments Flashcards
Knee Joint
Consists of 3 articulations:
- Lateral and medial articulations between the femoral and tibial condyles
- Patella and femur (patellofemoral joint)
Type: synovial hinge
Movements: flex/ext, some rotation when knee is flexed
Relatively weak b/c of incongruence of articular surfaces
Stability comes from muscles and ligaments
Knee Joint Capsule
Strong and covers entire surface of joint, except for anterior surface
Patella and patellar ligament serve as joint capsule anteriorly
Strengthened by 5 extracapsular ligaments:
- Patella ligament
- Fibular (lateral) collateral ligament
- Tibial (medial) collateral ligament
- Oblique popliteal ligament
- Arcuate popliteal ligament
Patella Ligament
Distal part of the quad tendon that extends from apex of patella to tibial tuberosity
Has connective tissue expansions that join with fibers of vastus medialis and lateralis to form patella retinaculum, which provides add’l support to knee joint
Below: infrapatellar fat pad, which helps provide cushioning to knee joint in kneeling
This ligament is struck for knee jerk reflex
Fibular (Lateral) Collateral Ligament
Round, cordlike ligament that extends inferiorly from lateral epicondyle of femur to lateral surface of head of fibula
Tendon of popliteus muscle passes deep to ligament, separating it from lateral meniscus
Tendon of biceps femoris is split into 2 parts by this ligament
Tibial (Medial) Collateral Ligament
Extends from medial epicondyle of femur to proximal medial surface of tibia
MCL is weaker than LCL and damaged more often
Deep fibers of MCL are tightly adhered to medial meniscus, causing medial meniscus to be commonly torn when MCL is damaged
MCL and LCL Purpose
Stabilize kneet joint on each side
Tight during extension, which helps prevent rotation of tibia on femur
In flexion, both are slack and not effective in preventing rotation
MCL torn by lateral blow to knee
LCL torn by medial blow to knee
Intra-Articular Ligaments of Knee
Consists of cruciate ligaments and menisci
Cruciate ligaments are located inside capsule, in b/w medial and lateral femoral condyles
Important for holding femur and tibia together, esp in flexion
Anterior Cruciate Ligament (ACL)
Weaker of the 2
Goes from anterior intercondylar region of tibia, runs superiorly, posteriorly, and laterally to attach to posterior medial side of lateral condyle of femur
Also attaches to medial meniscus
Poor blood supply
Taut in ext, slack in flex
Helps prevent:
- Anterior displacement of tibia on femur, posterior displacement of femur on tibia
- Hyperextension of knee joint
Posterior Cruciate Ligament (PCL)
Stronger of the 2
Attaches from posterior intercondylar region of tibia, passes superiorly, anteriorly, and medially to attach to anterior, lateral surface of medial condyle of femur
Tight during flexion of knee
Helps prevent:
- Anterior displacement of femur on tibia, posterior displacement of tibia on femur
- Hyperflexion of knee
During weight-bearing flexion, such as walking, it’s the main stabilizer
Menisci
C-shaped fibrocartilage that lap on top of articular surfaces of tibia
Helps deepen articular surfaces and act as shock absorbers
Thick at periphery and thin out at center
Menisci Ligaments
Coronary ligaments - capsular fibers that attach margins of menisci to tibial condyles
Transverse ligament of knee - joins anterior edge of menisci together, allowing them to move during movement of knee
Posterior meniscofemoral ligament - joins lateral meniscus to PCL and medial femoral condyle
Popliteus
When standing with knee locked in ext, popliteus acts to rotate femur laterally, releasing knee from locked position and allowing flex to occur
When the foot is off the ground and knee is locked into ext, popliteus unlocks knee by medially rotating tibia on femur
Popliteal Fossa
Diamond shaped space posterior to knee that serves as passageway for all important nerves and blood vessels on their way to lower leg
Borders:
- Superolateral: biceps femoris
- Superomedial: semimembranosus and semitendinosus
- Inferiolateral: lateral head of gastrconemius
- Inferiomedial: medial head of gastrocnemius
Popliteal Fossa Contents
Roof: skin and popliteal fascia
Floor: popliteal surface of femur, posterior capsule of knee, and popliteus muscle and fascia
Contents:
- Termination of small saphenous vein
- Popliteal artery and vein
- Tibial and common fibular nerves
- Medial and lateral sural cutaneous nerves
- Popliteal lymph nodes
