Knee

The knee is the largest and most complex joint in the human body, connecting the femur (thigh bone) to the tibia (shin bone) and the patella (kneecap). It functions mainly as a hinge joint that allows flexion and extension, with a small amount of rotation when bent. The joint relies on bones, cartilage, ligaments, tendons, muscles, and cartilage cushions to work smoothly.

Anatomy and structure: The knee comprises the distal end of the femur, the proximal end of the tibia, and the patella. Articular cartilage covers the contact surfaces, and the menisci (medial and lateral) are two crescent-shaped fibrocartilage wedges that absorb shock and improve stability. Stabilization is provided by the cruciate ligaments inside the joint (anterior and posterior) and the collateral ligaments on the sides (medial and lateral). The joint capsule and synovial membrane enclose the area, with surrounding tendons (including the quadriceps and patellar tendons) and muscles contributing to movement. The popliteal region behind the knee contains vessels and nerves.

Function and biomechanics: The knee supports body weight during standing and locomotion, allowing bending, straightening, and limited rotation. The screw-home mechanism between near-extension positions contributes to locking the knee during standing. Proper tracking of the patella within the femoral groove is essential for efficient movement and load distribution.

Clinical significance: Common issues include ligament injuries (such as ACL or MCL tears), meniscal tears, patellar dislocations, tendonitis, and osteoarthritis. Diagnosis relies on physical examination and imaging (X-ray, MRI). Treatments range from conservative approaches—rest, physical therapy, bracing, injections—to surgical options like ACL reconstruction, meniscal repair, or knee replacement, depending on severity and patient factors.