The knee is divided into compartments ( medial, lateral and patellofemoral). Every knee has two menisci, two collaterals and two cruciate ligaments.
Menisci are triangular fibrocartiliginous discs. Medial and lateral meniscus lie on either side. Meniscus though basically a shock absorber have many important functions. It prevents synovial impingement during flexion extension of knee. It aids in weight transmission and stabilises knee in rotations.
There are two cruciate ligaments, one anterior and other posterior. They cross each other hence the name cruciate. These ligaments have anteromedial and posterolateral portions. They are primary rotary stabilisers of knee and give protection during translation.
On either side of knee are collaterals 1. medial and 2. lateral. Collaterals provide stability against angulation.
The hamstrings and quadriceps moves the joint.
Flexion range of knee is from 0 to 120 degrees with hip extended and 160 degrees flexed. Extension is around 20 degrees. There is unique property of knee to get locked in extension. This minimises need of muscles.
Knee takes half the body weight on standing and six times body weight while strenuous flexion. High stresses causes knee injuries common, especially in high velocity and contact sports.
