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The challenge of treating cartilage damage in the knee

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I recently gave a lecture on this topic at the World Congress Orthopaedic, and it inspired me to write about this topic. Patients often ask me why cartilage damage is so difficult to treat. I hope this will give you a deeper understanding of complexity of cartilage injuries in the knee.

Articular cartilage damage in the knee presents a formidable challenge in the field of orthopaedic medicine. This smooth, white tissue covers the ends of bones, enabling slick, friction-free movement. When this vital tissue is damaged, the path to effective treatment is fraught with difficulties. Here’s a deep dive into why it’s so hard to treat articular cartilage damage in the knee.

1. Limited Healing Capacity

Articular cartilage (also called hyaline cartilage) has a very limited capacity for self-repair. Unlike other tissues in the body, it lacks blood vessels, nerves, and lymphatics. Blood vessels are crucial for delivering the necessary nutrients and cells that aid in the healing process. Without these, the regenerative capacity of cartilage is severely restricted, making spontaneous healing impossible.

2. Complex Biomechanics

The knee joint is subjected to complex and significant biomechanical forces. It supports much of the body’s weight and endures repetitive stress from activities like walking, running, and jumping. This constant load-bearing and movement make it difficult for any repair process to succeed. Even minor imperfections in the repaired cartilage can lead to significant biomechanical dysfunction. The cartilage behind the kneecap (patella) is especially vulnerable as a lot of shear forces go through area, including 5 times your body weight when walking downhill or downstairs.

3. Current Treatment Limitations

Several surgical treatments are available for cartilage damage. The three most commonly used are listed below, but each has its limitations:

  • Microfracture Surgery: This procedure stimulates the production of new cartilage by creating small fractures in the underlying bone. However, the new cartilage formed is fibrocartilage, which is not as durable or smooth as the original hyaline cartilage.
  • Autologous Chondrocyte Implantation (ACI): This involves harvesting cartilage cells, growing them in a lab, and then re-implanting them into the defect. While promising, it is a complex, multi-step process that is expensive and requires significant recovery time.
  • Osteochondral Grafting: Transferring healthy cartilage from a non-weight-bearing area to the damaged site can be effective, but it is limited by the amount of healthy donor cartilage available and can sometimes lead to donor site morbidity.

4. Degenerative Nature of Damage

Often, cartilage damage is not isolated but occurs as part of a degenerative process, such as osteoarthritis. In these cases, the damage is progressive and ongoing, complicating efforts to repair or regenerate the tissue. Treating the symptoms may provide temporary relief, but addressing the underlying degenerative process remains a major challenge.

5. Technological and Biological Hurdles

Advancements in biotechnology and materials science hold promise, but they also come with hurdles:

  • PRP injection: Several studies have shown that PRP injections can lead to significant reductions in pain and improvements in knee function. This is particularly evident in early stages of osteoarthritis and mild to moderate cartilage damage
  • Stem Cell Therapy: While research into stem cells for cartilage regeneration is ongoing, controlling the differentiation of stem cells into stable and functional cartilage tissue is complex and not yet fully understood.
  • Tissue Engineering: Creating bioengineered cartilage that mimics the natural structure and function of articular cartilage is still in its infancy. Issues with integration, durability, and functionality need to be resolved before this can become a mainstream treatment option.

6. Patient Factors

Individual patient factors also play a significant role. Age, weight, activity level, and the extent of cartilage damage all influence treatment outcomes. For instance, younger patients may have a better healing response than older patients, and those with higher activity levels might experience more wear and tear on repaired cartilage.

7. Rehabilitation Challenges

Post-treatment rehabilitation is crucial for success and is often long. It is very important to have a good physiotherapist to help guide your recovery. It requires a tailored program to gradually restore function while avoiding excessive stress on the healing cartilage.


Treating articular cartilage damage in the knee is inherently difficult due to reasons outlined above. After writing a thesis on the subject, and active involvement in ongoing research, my team and I are able to devise a bespoke, tailor-made management plan to help patients return to the activities they enjoy. If you think you might benefit from my expertise in this area, please do get in contact.

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