26/07/2024
🌟🦵 Anatomy and Biomechanics of the Knee Joint 🦵🌟
The knee joint, also known as the hinge joint, is the largest joint in the human body! It's a complex structure where the femur, tibia, and patella meet, forming the femorotibial and femoropatellar joints, all encased within a shared joint capsule. 🦴✨
The knee joint features two connective menisci that adapt the joint surfaces during movement. It's supported by both external ligaments (collateral ligaments and the joint capsule) and very strong internal ligaments, namely the anterior cruciate ligament (ACL) and posterior cruciate ligament (PCL). 🧬💪
Here's a quick breakdown:
🔸 Bones involved: Femur, tibia, and patella.
🔸 Joint head: Convex femoral condyles.
🔸 Joint socket: Slightly concave tibial condyles and patellar articular surface.
🔸 Joint capsule: Consists of an outer fibrous layer and an inner synovial membrane, uniquely layered in the knee.
🔸 Menisci: Lateral and medial menisci, slightly differing in size, which:
Deepen and fit the articular surfaces.
Allow rotational movements in the bent knee by sliding over the tibial surface. 🔄
Around the knee joint are several synovial bursae, often connected to the joint cavity, including:
🌟 Suprapatellar bursa
🌟 Subcutaneous infrapatellar bursa
🌟 Deep infrapatellar bursa
🌟 Semimembranosus bursa
🌟 Subcutaneous prepatellar bursa
🌟 Gastrocnemius bursa
🌟 Popliteal recess
Due to the high forces transmitted through the knee, the joint capsule is reinforced by many ligaments. The additional stability is provided by the cruciate ligaments and ligaments associated with the menisci, all surrounded by the fibrous capsule. We distinguish between external ligaments (medial collateral ligament, lateral collateral ligament, patellar ligament, patellar retinacula, oblique popliteal ligament, arcuate popliteal ligament) and internal ligaments (ACL, PCL, transverse ligament of the knee, anterior meniscofemoral ligament, posterior meniscofemoral ligament). 🔧🔗
The knee's movements include mainly flexion and extension, occurring around an axis passing through the femoral condyles, perpendicular to the length of the limb. The flexion and extension motion is a combination of rolling and gliding. Initially, up to around 20˚, the femur rolls over the tibia. Further movement transitions into gliding. The active range of flexion in the knee joint is 130˚, with passive reaching 160-170˚. A physiological hyperextension can go up to 10-20˚. The muscles involved in knee flexion are: the semitendinosus, semimembranosus, biceps femoris, gracilis, sartorius, gastrocnemius, and popliteus, while the muscles extending the knee are the quadriceps femoris and articularis genus. Rotational movements are minimal, being most pronounced at 90˚ flexion. The knee is most stable in extension. 🏃♂️💥
Keep your knees healthy and strong! 🌟💪