Knee Anatomy Quiz: Test Your Knowledge of the Knee Complex

Study Notes

The knee complex consists of two articulations: the tibia-femoral joint and the patello-femoral joint.
The tibia-femoral joint is a hinge joint with active motion only around one axis (flexion/extension).

The proximal articular surface of the knee joint is the distal end of the femur, which has large medial and lateral condyles.
The medial condyle extends further distally, making the distal end of the femur essentially horizontal.
The condyles show slight convexity in the frontal plane and are separated inferiorly by the intercondylar notch and anteriorly by the patellar groove.

The distal articular surface of the knee joint is the proximal tibia, which has asymmetrical medial and lateral tibial condyles or plateaus.
The medial tibial plateau is longer in the anteroposterior direction, but the lateral tibial articular cartilage is thicker.
The tibial plateaus are predominantly flat, with a slight convexity at the anterior and posterior margins.

The menisci are fibrocartilaginous structures found between the femur and tibia, with the medial meniscus being crescent shaped and the lateral meniscus being oval shaped.
The menisci are avascular and receive nutrition through blood vessels at the periphery and diffusion of synovial fluid at the center.
The menisci absorb shock, provide load distribution, and reduce friction between the tibia and femur.
The medial meniscus is more firmly attached to the joint capsule and has more capsular restraints, making it more prone to injury.

The degree of load distribution by the meniscus depends on the degree of genu varum, with greater compression on the medial meniscus in the presence of genu varum.
The greater the degree of genu valgum, the greater the compression is on the lateral meniscus.

The horns of the menisci and the peripheral vascularized portion of the meniscal bodies are well innervated with free nerve endings (nociceptors) and three different mechanoreceptors (Ruffini corpuscles, paciinian corpuscles, and Golgi tendon organs).
Proprioceptive deficits may potentially occur after meniscal injury due to injury to the mechanoreceptors within the meniscus.

The joint capsule encloses the tibiofemoral and patellofemoral joints.
The joint capsule is reinforced medially, laterally, and posteriorly by capsular ligaments.
The joint capsule is strongly innervated by both nociceptors as well as paciinian and ruffini corpuscles.
These mechanoreceptors may contribute to muscular stabilization of the knee joint by initiating reflex-mediated muscular responses.

The anatomic (longitudinal) axis of the femur is oblique, directed inferiorly and medially from its proximal to distal end.
The anatomic axis of the tibia is directed almost vertically.
The femoral and tibial longitudinal axes normally form an angle laterally at the knee joint of 171° (range from 170 to 175), which is called Physiological Valgus angle.
The femur is angled up to 5-10° off vertical, creating a slight physiologic (normal) valgus angle at the knee.

The Q-angle is the angle between the line of quadriceps femoris force and the direction of patellar tendon.
An increased Q-angle is a risk factor for patellar subluxation.
Q angles according to gender: 10-14° (men), 14-17° (women).

The patella is pushed to lateral by quadriceps femoris due to Q angle (about 10°).
This effect is controlled/limited by vastus lateralis, iliotibial band, lateral patellar retinaculum, and more prominent of lateral patellar surface.