Articular surfaces and menisci
The knee joint is formed by the articulation of multiple bone structures, which allows it to be classified as compound. The structures participating in its formation include:
- Condyles of the femur.
- Condyles of the tibia.
- Patella (patella).
A critical feature of the joint is the presence of specialized cartilaginous structures within its cavity — two menisci (medial and lateral). The presence of these intra-articular elements makes this joint complex. The joint capsule itself is relatively thin, but its mechanical strength is ensured by powerful reinforcement posteriorly and along the lateral surfaces.
Ligamentous apparatus of the knee
The numerous ligaments of the knee joint ensure its stability and are divided into two major topographical groups:
1. Intracapsular ligaments These structures are located directly within the joint cavity:
- Anterior cruciate ligament (lig. cruciatum anterius, ACL).
- Posterior cruciate ligament (lig. cruciatum posterius, PCL).
- Transverse ligament of the knee (lig. transversum genus), which spans between the two menisci.
2. Extracapsular ligaments These blend into the capsule externally or pass superficially over it:
- Tibial collateral ligament (lig. collaterale tibiale) and fibular collateral ligament (lig. collaterale fibulare), which reinforce the joint laterally.
- Patellar ligament (lig. patellae) — is the direct continuation of the tendon of the powerful quadriceps muscle.
- Medial and lateral patellar retinacula (retinacula patellae).
- Oblique and arcuate popliteal ligaments (lig. popliteum obliquum et arcuatum), which stabilize the posterior surface.
Synovial bursae and movements
To reduce friction of muscles and tendons, synovial bursae are located around the joint. Among numerous such structures, the infrapatellar, subtendinous, and other bursae are distinguished.
Biomechanically, the articulatio genus is a condylar joint. Movements in it occur around two axes:
- Frontal axis: responsible for the main amplitude movements — flexion and extension.
- Vertical axis: allows limited rotation, although this movement is physiologically feasible exclusively when the knee is flexed.
To remember the intracapsular ligaments, use the phrase "Cruciates and transverse": anterior/posterior cruciate (ACL/PCL) and the transverse ligament (between the menisci).
Class and exam questions
Why is the knee joint called both compound and complex?
It is compound due to the participation of more than two bone structures (femoral condyles, tibia, and patella). It is called complex due to the presence of additional cartilaginous elements in the joint cavity — the medial and lateral menisci.
What is the anatomical nature of the patellar ligament?
The patellar ligament (lig. patellae) is an extracapsular ligament that is essentially the anatomical continuation of the tendon of the quadriceps femoris muscle.
Under what condition is rotation possible in the knee joint?
Rotation around the vertical axis in the knee joint is severely restricted and is possible exclusively when the knee is flexed.
What else to study on this topic
- Functional anatomy of the anterior and posterior cruciate ligaments (ACL and PCL).
- Structure and role of the medial and lateral menisci in knee biomechanics.
- Topography of synovial bursae: infrapatellar and subtendinous.
- Features of the condylar joint as a biomechanical model.
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