How Cartilage Breaks Down: Understanding the Science of Joint Degeneration

Key Takeaways

• Cartilage is the smooth, slippery tissue that cushions your joints and allows bones to glide smoothly
• Unlike other tissues, cartilage has no blood supply and gets nutrients from synovial fluid
• In osteoarthritis, cartilage breaks down faster than your body can repair it, leading to pain and stiffness
• Once damaged, cartilage has limited ability to heal itself
• Many treatments focus on protecting remaining cartilage or replacing lost synovial fluid

If you’ve been told you have osteoarthritis, you’ve probably heard that your cartilage is wearing away. But what does that actually mean? Understanding how cartilage breaks down can help you make sense of your symptoms and why certain treatments work.

What Is Cartilage and Why Does It Matter?

Think of cartilage as the shock absorber in your joints. It’s a firm but flexible tissue that covers the ends of your bones where they meet. When cartilage is healthy, it creates a smooth, slippery surface that lets your bones glide past each other without friction.

What makes cartilage special:

• Smooth surface: About 10 times more slippery than ice on ice
• Shock absorption: Compresses under pressure to absorb impact
• No nerves: Healthy cartilage doesn’t hurt when damaged (the pain comes from other joint tissues)
• No blood vessels: This is crucial—cartilage can’t heal like other tissues because it doesn’t have its own blood supply

Your knee cartilage, for example, is only about 2-4 millimeters thick. That’s roughly the thickness of two credit cards stacked together. Yet this thin layer does an enormous job protecting your bones during every step, squat, and stair climb.

The Unique Challenge: How Cartilage Gets Nutrients

Here’s where things get interesting. Most tissues in your body heal when damaged because blood carries nutrients and repair cells to the injury site. But cartilage is different—it has no blood supply at all.

Instead, cartilage gets its nutrients from synovial fluid, the thick, gel-like liquid that fills your joint space. Think of synovial fluid as the oil in your car engine. It lubricates moving parts and carries nutrients to cartilage cells.

How it works:

1. When you move your joint, pressure squeezes old synovial fluid out of the cartilage
2. When you release pressure, fresh synovial fluid soaks back in, bringing nutrients
3. This “pump action” keeps cartilage cells alive and functioning

This is why movement is so important for joint health. Staying active keeps this nutrient pump working. But it also explains why cartilage is vulnerable—it depends entirely on the quality and quantity of your synovial fluid.

The Breakdown Process: What Happens in Osteoarthritis

Osteoarthritis doesn’t happen overnight. It’s a gradual process that can take years or even decades. Here’s what researchers believe happens:

Stage 1: Early Changes

The process often starts with changes to your synovial fluid. As you age or after an injury, your synovial fluid can become:

• Thinner and less viscous (less “gel-like”)
• Lower in hyaluronic acid, the substance that gives synovial fluid its cushioning properties
• Less able to nourish and protect cartilage

With poorer quality synovial fluid, your cartilage doesn’t get the nutrients and protection it needs.

Stage 2: Surface Damage

Without adequate lubrication and nourishment, the smooth cartilage surface starts to deteriorate:

• The surface becomes rougher and develops tiny cracks
• Cartilage cells (called chondrocytes) start to die
• The cartilage loses its ability to absorb shock

At this stage, you might not notice any symptoms yet. The damage is happening at a microscopic level.

Stage 3: Inflammation and Faster Breakdown

As cartilage breaks down, tiny fragments float into the joint space. Your immune system sees these fragments as foreign invaders and triggers inflammation. This creates a vicious cycle:

1. Inflammation releases enzymes that break down cartilage even faster
2. More cartilage fragments cause more inflammation
3. The joint becomes swollen, warm, and painful

This is when most people start experiencing symptoms—pain, morning stiffness, and swelling after activity.

Stage 4: Bone-on-Bone Contact

In advanced osteoarthritis, so much cartilage has worn away that bones can rub directly against each other. This causes:

• Severe pain during movement
• Bone spurs (extra bone growth at joint edges)
• Significant loss of mobility
• Visible joint deformity in severe cases

Why Cartilage Can’t Heal Itself

You might wonder: if cartilage breaks down, why doesn’t my body just rebuild it?

The problem goes back to that lack of blood supply. When you cut your skin, blood rushes to the wound carrying repair cells, nutrients, and growth factors. Healing happens quickly. But cartilage doesn’t have this repair system.

Limited healing capacity:

• Cartilage cells (chondrocytes) divide very slowly, if at all
• Without blood supply, repair cells can’t reach damaged areas
• The joint environment (with all those inflammatory chemicals) doesn’t encourage healing

Small cartilage injuries sometimes develop scar tissue, but this “repair cartilage” is fibrous and doesn’t work as well as the original. It’s more like duct tape than proper repair—it might help temporarily, but it’s not as good as the real thing.

What This Means for Treatment

Understanding cartilage breakdown helps explain why certain treatments work and why there’s no simple “cure” for osteoarthritis.

Current treatments aim to:

Slow the Breakdown Process

• Weight loss reduces pressure on weight-bearing joints
• Exercise strengthens muscles that support and protect joints
• Anti-inflammatory medications reduce the chemicals that speed up cartilage destruction

Protect Remaining Cartilage

• Proper footwear and assistive devices reduce impact forces
• Activity modification prevents excessive wear
• Physical therapy improves joint mechanics

Replace Lost Lubrication

This is where treatments like viscosupplementation come in. These gel injections (with brands like Synvisc, Euflexxa, and others) add hyaluronic acid back into your joint space—essentially replacing the cushioning component your body can’t maintain anymore.

The goal is to:

• Improve lubrication between joint surfaces
• Reduce friction and further cartilage damage
• Provide better nourishment to remaining cartilage cells
• Reduce pain and inflammation

Think of it as changing the oil in your car. It won’t fix existing engine damage, but it can help protect what’s left and improve how things run.

Manage Pain and Function

• Pain medications address symptoms while protecting cartilage
• Cortisone injections reduce inflammation during flare-ups
• Physical therapy maintains mobility and strength

The Bottom Line

Cartilage breakdown in osteoarthritis is a complex biological process, but it boils down to a few key problems:

1. Poor lubrication: Synovial fluid becomes thin and less protective
2. Inadequate nourishment: Cartilage cells don’t get what they need to survive
3. Increased wear: Without proper cushioning, mechanical stress damages cartilage
4. Inflammation: The body’s response to damage speeds up the breakdown
5. Limited repair: Cartilage can’t heal itself effectively

The good news is that understanding this process gives us targets for treatment. While we can’t reverse severe cartilage loss, we can often slow the process, manage symptoms, and maintain function for years.

If you’re dealing with osteoarthritis, working with your healthcare provider to address each stage of the breakdown process—protecting remaining cartilage, reducing inflammation, and potentially restoring some lubrication—gives you the best chance of staying active and comfortable.

Frequently Asked Questions

Can cartilage grow back?

Unfortunately, cartilage has very limited ability to regenerate. Some experimental treatments aim to stimulate cartilage growth, but for most people with osteoarthritis, the focus is on protecting remaining cartilage and managing symptoms rather than regrowing lost tissue.

Does taking glucosamine or chondroitin help rebuild cartilage?

Research on these supplements is mixed. Some studies show modest benefits for pain relief, but there’s no strong evidence they rebuild cartilage. They’re generally safe to try, but manage expectations—they won’t reverse arthritis.

How long does it take for cartilage to break down?

This varies widely. Some people develop significant osteoarthritis over 5-10 years, while others have slow progression over decades. Factors like genetics, joint injuries, weight, and activity level all play a role.

If I have cartilage damage, will I definitely need surgery?

Not necessarily. Many people with moderate osteoarthritis manage well with non-surgical treatments for many years. Surgery (like joint replacement) is typically reserved for severe cases where other treatments haven’t provided adequate relief.

Can exercise make cartilage breakdown worse?

The right exercise actually helps by maintaining synovial fluid circulation and strengthening supporting muscles. High-impact activities might accelerate wear in damaged joints, but low-impact exercise (walking, swimming, cycling) is beneficial for most people with osteoarthritis.

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This article is for informational purposes only and does not replace professional medical advice. Consult your healthcare provider for personalized recommendations about your joint health.

Last medically reviewed: March 2025