Introduction

Articular cartilage is a specialised, smooth tissue that covers the ends of bones in our synovial joints – the type of joints that move freely like knees, hips, and ankles. Made up mainly of a dense network of collagen and proteoglycans, with few specialised cells called chondrocytes, it acts as a cushion and allows bones to glide effortlessly over one another.

Understanding articular cartilage is essential in maintaining joint health and managing musculoskeletal problems. Because it lacks blood vessels and nerves, it cannot repair itself easily. Injuries to this cartilage, especially in weight-bearing joints such as the knees and ankles, are common and often lead to pain, reduced movement, and conditions like osteoarthritis. As noted by Wang and colleagues (2024), “due to lack of blood vessels and nerves, the ability of cartilage to self-repair is limited.”

Articular Cartilage: Structure and Function

Articular cartilage is a type of hyaline cartilage, which appears glossy and translucent under the microscope. Its structure is dominated by type II collagen fibres embedded in a gel-like matrix rich in water-binding molecules called proteoglycans, such as aggrecan. This arrangement provides the cartilage with the strength, flexibility, and resilience it needs to perform its role. The cartilage is organised into layers from the surface down to the bone, each with slightly different features that help absorb shock and bear weight.

In contrast, fibrocartilage, which contains more of the tougher type I collagen, is found in areas that need to withstand pulling forces, like the menisci in the knee or intervertebral discs.

Articular cartilage’s job is to distribute the stress of movement evenly across the joint, absorb shocks, and reduce friction to allow smooth, pain-free motion. However, because it lacks blood flow and nerves, its natural ability to heal is very limited, making damage potentially serious.

A key player in keeping cartilage healthy is the protein SOX9. Research by Haseeb et al. (2021) reveals that SOX9 “prevents growth-plate closure and preosteoarthritic deterioration of articular cartilage” by maintaining the identity of cartilage cells, helping to prevent degeneration.

Understanding these differences helps physicians tailor treatments and predict outcomes when cartilage is injured.

Articular Cartilage Injuries: Causes, Symptoms and Pain

Articular cartilage injuries often happen through sudden trauma, such as a sports injury or accident, but can also occur gradually due to ageing or repeated stresses on the joint. The knee is a frequent location for such injuries, with patients experiencing pain, swelling, stiffness, and sometimes sensations of locking or clicking within the joint. Pain is often focused on the joint line and can significantly affect everyday activities.

Doctors diagnose cartilage damage through physical examination and imaging, typically MRI scans, which allow clear views of cartilage condition. Sometimes arthroscopy—a minimally invasive surgery using a camera inside the joint—is needed to assess the damage directly.

The time it takes to recover depends on the extent of injury. Minor damage may improve over weeks or months with non-surgical care, but more severe lesions might require surgery and longer rehabilitation.

Managing pain commonly involves medications, physiotherapy, and modifying activities to protect the joint while allowing healing.

Contemporary Treatments and Rehabilitation

Treatment for articular cartilage injuries often starts with conservative methods. This includes rest, pain relief, and carefully designed exercises, particularly for the knee, which help maintain joint strength and mobility without overloading damaged areas.

Increasingly, therapies that involve injecting substances like hyaluronic acid or platelet-rich plasma into the joint are being used to support cartilage repair and reduce symptoms.

The “best medicine for cartilage repair” is often a balanced approach tailored to the individual’s needs and injury severity. Rehabilitation aims to progressively increase joint movement and strength, promoting recovery while preventing further harm.

At the forefront of this care is Professor Paul Lee at the London Cartilage Clinic, who combines cutting-edge orthopaedic techniques with personalised, compassionate care to support patients fully on their journey to recovery.

The Future of Articular Cartilage Care

Exciting new developments are on the horizon. Tissue engineering and regenerative medicine are exploring ways to encourage the body to rebuild damaged cartilage. Wang et al. (2024) describe how “stimuli-responsive smart scaffolds, 3D-printed scaffolds, and cartilage bionic scaffolds” offer fresh hope for more effective treatments.

Furthermore, cell-based therapies are showing promise. Abe and colleagues (2023) report that “allogeneic iPSC-derived cartilage organoids survive and integrate with surrounding native cartilage without immune reactions in a primate model,” suggesting these may become treatments for cartilage defects in humans. However, more research is needed to understand their long-term effectiveness in load-bearing joints.

Maintaining cartilage health also means protecting the identity of cartilage cells. Haseeb et al. (2021) highlight the role of SOX9 in “safeguarding the lineage fate of chondrocytes by preventing their dedifferentiation and conversion into bone cells,” a process important in preventing joint degeneration.

Achieving the best outcomes will increasingly rely on personalised care and teamwork among specialists — from surgeons to physiotherapists — who tailor treatments to each patient’s unique needs.

If you have joint concerns, it’s important to seek advice from qualified healthcare professionals who can provide expert, evidence-based care.

For individual medical advice, please consult a qualified healthcare professional.

References

• Wang, M., Wu, Y., Li, G., Lin, Q., Zhang, W., Liu, H., & Su, J. (2024). Articular cartilage repair biomaterials: strategies and applications. MedComm: Biomaterials and Applications, 100948. https://doi.org/10.1016/j.mtbio.2024.100948
• Abe, K., Yamashita, A., Morioka, M., Horike, N., Takei, Y., Koyamatsu, S., Okita, K., Matsuda, S., & Tsumaki, N. (2023). Engraftment of allogeneic iPS cell-derived cartilage organoid in a primate model of articular cartilage defect. Nature Communications, 14, 701. https://doi.org/10.1038/s41467-023-36408-0
• Haseeb, A., Kc, R., Angelozzi, M., de Charleroy, C., Rux, D., Tower, R., Yao, L., Pellegrino da Silva, R., Pacifici, M., Qin, L., & Lefebvre, V. (2021). SOX9 keeps growth plates and articular cartilage healthy by inhibiting chondrocyte dedifferentiation/osteoblastic redifferentiation. Proceedings of the National Academy of Sciences, 118(7), e2019152118. https://doi.org/10.1073/pnas.2019152118