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Which type of joint us knee joint

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The Knee Joint - Type and Classification

The knee joint is a modified hinge joint (also called a bicondylar synovial joint).
More precisely, it is classified as:
Classification LevelType
Structural typeSynovial joint (diarthrodial)
Functional/movement typeModified hinge joint
Specific subtypeBicondylar joint
Knee Joint Anatomy - Gray's Anatomy for Students

Why "Modified" Hinge?

A pure hinge joint allows movement in only one plane (like the elbow). The knee is called "modified" because it allows:
  • Flexion and extension (primary movements, like a hinge)
  • Limited medial and lateral rotation - especially the "screw-home mechanism" (terminal external rotation of the tibia when the knee fully extends, "locking" it)
As stated in Rosen's Emergency Medicine: "The knee is a modified hinge, diarthrodial synovial joint that consists of the tibiofemoral and patellofemoral joints."
And from Rheumatology (Elsevier, 2022): "The knee joint functions as a modified hinge joint that allows flexion and extension, together with some limited rotation."

Component Articulations

The knee joint is actually made up of three articulations within a single joint capsule:
  1. Medial tibiofemoral joint - between medial femoral condyle and medial tibial condyle
  2. Lateral tibiofemoral joint - between lateral femoral condyle and lateral tibial condyle
  3. Patellofemoral joint - between the patella and the femoral trochlea

Key Structural Features

  • Menisci - two C-shaped fibrocartilaginous discs (medial and lateral) that improve congruence and cushion the joint
  • Collateral ligaments (MCL and LCL) - provide medial/lateral stability
  • Cruciate ligaments (ACL and PCL) - prevent anterior/posterior displacement of the tibia on the femur
  • Synovial membrane - lines the joint cavity and produces synovial fluid for lubrication
  • Gray's Anatomy for Students, p. 709
  • Rosen's Emergency Medicine, Anatomy & Physiology section
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