Synovial Membrane: Structure, Functions, and Pathology

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Synovial membrane helps in the smooth movement of synovial joints of the body, whether it be the ball and socket joint or the hinge joint or the pivot joint, this membrane has unexpected and distinctive tasks to do, read below to learn more.


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What is Synovial Membrane?

The synovial membrane commonly termed as synovium or stratum synovial is a soft tissue lining which is very thin in the structure which acts as vascular connective tissue between two bones. These membranes are responsible for mediating the nutrient exchange between bone joint fluid and blood, found in synovial joints only.

There is a presence of intimal cells in the membrane which are sub-categorized into two types:

1. Type A: These are derived from macrophages synovial cells, which acts as the cleansing agent in the synovial fluid. It eliminates undesirable elements from the fluid and comprises of the 20% of the cell lining in the synovium.


2. Type B: These are derived from the fibroblast cells. Located in the deep layers which generate long-chain sugar polymer called hyaluronan which makes the synovial fibrous which lubricates the joint surfaces. Also, these are non-fixed cells with antigens present in them.


This membrane surrounds the bone joint and the sheath of the tendon to provide protection and stimulation. Also, the synovium stays in direct contact with the synovium fluid which has multiple purposes to serve for the bone joint.




What is the Structure of Synovial Membrane?

The synovium line the bursae, tendon sheaths, and joints. Bursae are located near the synovial joint where it facilitates the smooth movement between subcutaneous tissue and bone, or between two tendons. The Synovial Membrane is generally made up of two layers mentioned below.

  • The outer layer called subitima which is a fibrous connective tissue. It is loose in structure.
  • The inner layer called Intima which consists of sheets of cells thinner than a paper. It sits on a pliable membrane.


The surface of the synovium is flat which is cover by finger-like projections called villi. This helps the movement to be smooth and flexible by re-adjusting its shape according to the friction of the bones. Inside this membrane is the synovial fluid which acts as lubricant agent between the corresponding joint.


Structure of Synovial Membrane




What is the Function of Synovial Membrane?

The core purpose of this membrane is to provide a plane for separation and disconnection between the solid tissues which promotes the movement with relaxation and smoothness.


In case of lack of separation the joint tends to the disability of movement. Apart from the aforementioned, this membrane controls the volume of fluid in the cavity to allow the solid components to move freely against each other.


Another significant function of the synovium is to reshape itself to avoid any collision between the muscles and acting as the line-up between the bursae, tendon sheaths, and joints.


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What is Synovial Membrane Fluid?

This fluid is generated from an ultrafiltrate of blood plasma which is regulated by synovium. The sole purpose of this fluid is to lubricate the cartilage of the bone joint and nourish the diffusion.


It is believed that a healthy knee must consist at least 2ml of this fluid to regulate the motion properly.


The synovial membrane fluid is extremely helpful in reducing the friction between the joints with its egg white like consistency.


Also, this fluid falls under the category of non-Newtonian fluid as it doesn’t follow the laws of Newton in terms of viscosity. Tasks like nutrient and waste transportation and shock absorption are also made possible by this fluid.


In case of joint inflammation, swelling or redness, the doctor would recommend a synovial fluid analysis which involves the invasion of the large syringe needle to draw the fluid sample into it. This sample is further used to detect any traces of lactic dehydrogenase, uric acid, and protein which can be held responsible for inflammation.




What is the Pathology of Synovial Membrane?

There are risk factors, conditions, and diseases that are evolved in situations when the membrane is irritated or thickened. Some conditions and disease are enlisted below.

  • Rheumatoid arthritis
  • Osteoarthritis
  • Alkaptonuria
  • Scleroderma
  • Hemochromatosis
  • Tuberculous arthritis
  • Gout
  • Neoplasms





The synovial membrane is soft and thin membrane yet has various significant roles that are very essentials for our body movements that are dependent on the synovium joints. Try to stay hydrated, eat healthy diet involving green leafy vegetables, berries, and fishes maintain the positive health of this connective tissue.


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