Knee Anatomy and Biomechanics Lecture

Vocabulary flashcards covering the anatomical structures, ligaments, vascularity, and biomechanics of the knee joint based on the lecture transcript.

Joint Capsule

A fluid-filled, saran wrap-like structure enclosing the articular surface of a synovial joint that holds the synovial fluid.

Effusion

Swelling that consists of fluid accumulation inside the joint capsule (capsular swelling), as opposed to generalized superficial puffiness.

Arcuate Ligament

An extracapsular thickening on the posterior knee capsule that forms an arch from the posterior fibular head and helps prevent hyperextension.

Oblique Popliteal Ligament

A posterior capsular thickening that blends with the semimembranosus tendon at its insertion site and prevents hyperextension.

Screw Home Mechanism

The biomechanical locking of the knee in full extension driven by $10^\circ$ of external rotation of the tibia on the femur, tightening the major ligaments and allowing the quadriceps to relax during standing.

Popliteus Muscle

A posterior knee muscle originating on the lateral femoral condyle and inserting on the proximal posterior tibia; it unlocks the knee by internally rotating the tibia in open chain or externally rotating the femur in closed chain.

Patellar Retinaculum

Thin connective tissue running at downward angles medial and lateral to the patella; the medial retinaculum is typically disrupted during a lateral patellar dislocation.

Medial Collateral Ligament (MCL)

An extracapsular ligament running from the medial femoral epicondyle to the medial margin of the tibia, bonded to the capsule and resisting valgus forces.

Lateral Collateral Ligament (LCL)

An extracapsular ligament attaching from the lateral femoral condyle to the fibular head, separated from the joint capsule by the popliteus tendon, that resists varus forces.

Anterior Cruciate Ligament (ACL)

An intracapsular ligament attaching to the anterior intercondylar eminence of the tibia and ascending posteriorly to the lateral wall of the intercondylar fossa, preventing anterior tibial translation and hyperextension.

Posterior Cruciate Ligament (PCL)

An intracapsular ligament attaching posterior to the intercondylar eminence and ascending anteriorly to the medial wall of the intercondylar fossa, preventing hyperflexion and posterior translation of the tibia.

Unhappy Triad

A combined knee injury usually caused by a blow to the lateral side of the knee, resulting in simultaneous damage to the medial meniscus, MCL, and ACL.

Red Zone (Meniscus)

The peripheral $\frac{1}{3}$ of the meniscus that receives a direct blood supply from the popliteal artery and possesses healing capability.

White Zone (Meniscus)

The avascular inner $\frac{2}{3}$ of the meniscus that relies solely on synovial fluid for nourishment and rarely heals on its own when torn.

Popliteal Artery

The primary arterial vessel descending directly posterior to the knee in the popliteal space that gives off anastomotic genicular branches and supplies peripheral meniscal tissue.

Great Saphenous Vein

A superficial vein traversing the medial aspect of the leg, commonly harvested for coronary artery bypass graft (CABG) surgery.

Pes Anserine Bursa

A fluid-filled sac situated over the medial tibial condyle that protects the three conjoined pes anserine tendons from friction against the rough bone margin.

Sciatic Nerve

The large nerve descending through the posterior thigh that bifurcates near the posterior knee into the tibial nerve and common fibular nerve.