Follow-up to Post 1 - Further Histology of the Knee

           Histologically speaking, the knee joint is composed of a variety of different types of tissues, most of which are types of specialized connective tissues. These tissue types include bone, muscle, and cartilage. 
           Cartilage is a type of connective tissue specialized for supporting various body structures. There exist various forms of cartilage, three of which are hyaline cartilage, fibrocartilage, and elastic cartilage, which all differ in their composition (Volkoff, 2016). Specifically speaking about the knee and its cartilage, two types of cartilage are found within the knee joint. Lining the interior of the joint is articular cartilage, which is actually just hyaline cartilage. The hyaline cartilage here is nourished by the synovial fluid found within the joint cavity, not by perichondrium like hyaline cartilage found elsewhere. The second type of cartilage found in the knee joint is fibrocartilage. The meniscus of the knee are made of fibrocartilage, a dense, coarse connective tissue made up of type 1 collagen fibres. 

Figure 1 Overview of knee histology, with cartilage, bone, and muscle identified. Retrieved from https://secure.health.utas.edu.au/intranet/cds/cam102/Images/9x25.jpg 

            The type of bone tissues found in the bones of the knee joint are also of different types. The femur is an example. The long shaft (diaphysis) of the femur, and other long bones, is composed of compact bone, whereas the epiphysis of the femur is composed of spongy bone. Compact bone and spongy bone have somewhat similar arrangements, with cells and the matrix having a lamellar arrangement, but they differ in the arrangements of the lamellae. In compact bone, lamellae are arranged into osteons, whereas in spongy bone, they are arranged in trabeculae. Spongy bone has numerous spaces found between bone tissue which are filled with blood vessels to nourish the bone tissue as well as bone marrow. See the above figure for a summary of the different types of tissues found in the knee joint.

References
Volkoff, H. (2016). Cartilage. Memorial University of Newfoundland. 

Volkoff, H. (2016). Bone. Memorial University of Newfoundland.

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