Synovial Membrane

What is the synovial membrane?

The synovial membrane is a thin barrier that lines the inside of some of your joints. You might also see it referred to as your synovium.

Your synovial membranes encase your joints in a layer of synovial fluid. The fluid protects your joints and helps them move smoothly.

Synovial membranes are part of your musculoskeletal system that helps you sit, stand and move.

What does the synovial membrane do?

Your synovial membranes protect the joints they surround. They form what’s called a synovial capsule around your joints. They work with your cartilage, tendons and ligaments to reduce friction between the bones in your joints — especially when you’re moving them.

How the synovial membrane works depends on which kind of joint it’s protecting.

The synovial membrane in your elbow lubricates your joint as you bend and straighten your arm. It prevents the ends of your upper arm bone (humerus) and the bones in your lower arm (your radius and ulna) from rubbing together.

In your hip, the synovial membrane reduces friction between the rounded head of your thigh bone (femur) and the indented socket in your pelvis that it fits into.

Where are synovial membranes located?

Synovial membranes protect your joints that involve two bones moving together, including your:

• Elbows.
• Knees.
• Ankles.
• Feet.
• Fingers, thumbs and knuckles.
• Wrists.
• Shoulders.
• Hips.

How big is the synovial membrane?

Your synovial membranes are small. They can vary in size depending on which joint they’re surrounding, but they’re usually less than a third of an inch thick (around 1 centimeter).

What is the synovial membrane made of?

Your synovial membranes have two layers.

The inner layer (the intima) is thin and makes the synovial fluid that lubricates your joints.

The outer layer (the subintimal layer) is made of a tough, fibrous layer of cells that protects the inner layer. It’s flexible enough to move with your joint. The subintimal layer contains:

• Nerve cells.
• Lymphatic cells.
• Blood vessels.

Synovial fluid

The synovial fluid inside your synovial membranes lubricates the parts of your joint as they move. The fluid slides between pieces of bones or cartilage to help them move smoothly and without rubbing against each other. It’s made from the plasma in your blood.

What are common conditions that affect the synovial membrane?

Arthritis is the most common issue that will affect your synovial membranes — and the joints they protect. Forms of arthritis that commonly affect synovial membranes include:

• Osteoarthritis.
• Rheumatoid arthritis.
• Gout.

Other conditions can affect your synovial membranes, including:

• Repetitive strain injuries.
• Bursitis.
• Synovial sarcomas.

Talk to your healthcare provider if you notice any symptoms in your joints, including:

• Swelling.
• Pain that doesn’t get better in a few days.
• Tenderness.
• Difficulty moving a part of your body like you usually can.
• Discoloration or bruising.

What tests are done on the synovial membrane?

Your healthcare provider might need imaging tests of your joints to determine what’s causing your symptoms, including:

• MRI (magnetic resonance imaging).
• CT scan (computed tomography scan).
• Ultrasound.

Your provider might need to biopsy your synovial fluid to diagnose some conditions, like infections. This means they’ll take a small sample for analysis.

What treatments are used on the synovial membrane?

Which treatments you’ll need depends on what’s causing your symptoms.

Talk to your provider about treatments to help you feel better and reduce any symptoms in your joints.

Keeping your synovial membranes healthy

Following a good diet and exercise plan and seeing your healthcare provider for regular checkups will help you maintain your overall health. This includes your synovial membranes and joints.

You can lower your chances of developing arthritis by:

• Not using tobacco products.
• Doing low-impact, non-weight-bearing exercise.
• Maintaining a body weight that’s healthy for you.

Follow these general safety tips to reduce your risk of an injury to your joints:

• Always wear your seat belt.
• Wear the right protective equipment for all activities and sports.
• Make sure your home and workspace are free from clutter that could trip you or others.
• Always use the proper tools or equipment at home to reach things. Never stand on chairs, tables or countertops.
• Use your cane or walker if you have difficulty walking or have an increased risk for falls.

A note from Cleveland Clinic

If your synovial membranes are working correctly, you’ll never notice them. But — if you have pain or other symptoms in your joints — there’s a good chance something’s wrong with one of your synovial membranes.

Visit your provider if you’re in pain or experiencing any other symptoms with one of your joints. The sooner you get an issue diagnosed, the sooner you can get back to moving throughout your day without feeling uncomfortable.