What is Synovial Membrane?
The synovial membrane is the inner mucosal tissue of the articular capsule, appearing pale red. Generally, the synovial membrane is smooth and shiny, thin but soft and supple. It is composed of loose connective tissue, belonging to 1-3 layers of connective tissue cells. Under normal conditions, the synovial membrane secretes synovial fluid, which lubricates the joint during movement. Once the synovial membrane is damaged, it will affect the movement of the joint.
The synovial membrane is composed of matrix, cells, and fibers. The inner surface is smooth, with 1 to 3 layers of connective tissue cells, also known as synovial cells, which are visible under an electron microscope as separate cells connected by fine spines. The cells can be divided into two types based on their functional state. Synovial cells are related to the formation of hyaluronic acid in synovial fluid. Below the cell layer is a capillary network, followed by fibrous tissue. The thickness varies depending on the location and contains blood vessels, lymphatic vessels, and nerve fibers. The cellular components include fibroblasts, macrophages, mast cells, and adipocytes. The superficial layer of the synovial membrane can be regenerated from this layer or the fibrous layer of the articular capsule. Additionally, the synovial membrane also forms synovial bursas or sheaths in other parts of the body.
Acute synovitis of the knee joint refers to a non-infectious inflammatory reaction of the synovial membrane caused by acute trauma to the knee joint. This condition typically manifests as pathological changes such as congestion, edema, and hyperplasia of the synovial membrane tissue. The effusion from the synovial membrane tissue leads to intra-articular fluid accumulation, resulting in significant joint swelling and pain. If the acute phase is not effectively controlled, extensive proliferation and fibrosis of the synovial membrane tissue can easily lead to joint adhesion, forming recurrent chronic synovitis, severely affecting the patient's quality of life.
