Human Anatomy: Knee Ligaments Quiz

Ligaments

• Arcuate popliteal ligament strengthens the fibrous capsule posteriorly and arises from the posterior aspect of the fibular head.
• Lateral stabilization is provided by the biceps, gastrocnemius (lateral head), iliotibial tract, and fibular collateral ligament.
• Medial stabilization is provided by the sartorius, gracilis, gastrocnemius (medial head), semitendinosus, semimembranosus, and tibial collateral ligament.

Skin and Arterial Supply

• The infrapatellar branch of the saphenous nerve and the peripatellar plexus provide cutaneous innervation.
• The arterial supply of the skin covering the knee is from the genicular branches of the popliteal artery, the descending genicular branch of the femoral artery, the anterior recurrent branch of the anterior tibial artery, and small contributions from the arteries to vastus medialis and the hamstrings.

Posterior Aspect of Thigh and Knee Joint

• The semitendinosus and semimembranosus muscles originate from the ischial tuberosity and insert into the medial surface of the superior part of the tibia (semitendinosus) and the posterior part of the medial condyle of the tibia (semimembranosus).
• The semitendinosus and semimembranosus muscles are innervated by the tibial division of the sciatic nerve and extend the thigh, flex the leg, and rotate medially.
• The biceps femoris muscle originates from the ischial tuberosity and the linea aspera and lateral supracondylar line of the femur, and inserts into the lateral side of the head of the fibula.
• The biceps femoris muscle is innervated by the tibial and common fibular nerves and flexes the leg and laterally rotates; extends the thigh.

Knee Joint Anatomy

• The bones involved in the knee joint are the femur, tibia, fibula, and patella.
• The femur has medial and lateral femoral condyles that articulate with the tibia.
• The tibia has a flat tibial plateau that articulates with the femoral condyles.
• The fibula articulates with the tibia.
• The patella is a sesamoid bone that protects the anterior joint and is enclosed in the quadriceps/patellar tendon.

Knee Joint Structure

• The knee joint consists of the tibiofemoral joint (structurally a hinge joint and considered a condylar type of synovial joint), the patellofemoral joint (a saddle joint), and the superior tibiofibular joint.
• The tibiofemoral joint has lateral and medial articulations between the tibial condyles and their cartilaginous menisci and the corresponding femoral condyles.
• The articular surfaces are covered with hyaline cartilage.

Articular Capsule and Ligaments

• The articular capsule is thin and deficient in some areas, attaching superiorly proximal to the articular margins of the condyles and also intercondylar fossa posteriorly.
• The ligaments of the knee joint include intracapsular ligaments (cruciate ligaments and menisci) and extracapsular ligaments (patellar ligament, fibular collateral ligament, tibial collateral ligament, oblique popliteal ligament, and arcuate popliteal ligament).

Menisci

• The menisci are fibrocartilaginous discs that are thicker on the outside than inside, with poor blood supply.
• The menisci lie on top of the tibial plateau, increase stability, and make the condyles fit better.
• The menisci act as shock absorbers.

Ligaments

• The anterior cruciate ligament (ACL) runs from the anterior tibia to the posterior femur and prevents anterior displacement of the tibia on a fixed femur and excessive internal rotation.
• The posterior cruciate ligament (PCL) runs from the posterior tibia to the anterior femur and prevents posterior translation of the tibia on a fixed femur and excessive external rotation.
• The ACL and PCL "cross" or wrap around each other, becoming taut when in extension and looser when in flexion.
• The medial collateral ligament (MCL) attaches to the medial femoral epicondyle and anteromedial tibia and stabilizes against valgus stress applied to the lateral aspect of the joint capsule.
• The lateral collateral ligament (LCL) attaches to the lateral femoral epicondyle and head of the fibula and stabilizes against varus stress when force is applied to the medial aspect of the joint capsule.
• The oblique popliteal ligament is an expansion of the semimembranosus and strengthens the capsule posteriorly.