The knee joint relies on hyaline cartilage, a smooth tissue covering the ends of the femur and tibia bones. This tissue acts as a shock absorber and provides a low-friction surface, allowing the joint to move seamlessly. Hyaline cartilage lacks a direct blood supply, giving it an extremely limited ability to repair itself once damaged. Therefore, intervention focuses on maintenance, protection, and advanced repair techniques rather than simple regeneration.
Optimizing Joint Load Through Weight Management and Exercise
Reducing mechanical stress is the most fundamental non-invasive strategy for preserving existing cartilage. Body weight directly correlates with the load experienced by the knees. Studies indicate that every pound of weight lost results in a four-fold decrease in the load exerted on the knee during walking. Losing just 5 to 10% of total body weight slows the rate of cartilage degeneration.
Low-impact physical activity is important for cartilage health. Gentle, repetitive motion helps circulate the joint fluid that nourishes the tissue. Exercises like cycling, swimming, rowing, and using an elliptical machine provide necessary cyclic loading without the high compressive forces of running or jumping. These activities stimulate cartilage cells to maintain a healthy matrix.
Strengthening the muscles surrounding the knee provides dynamic support and stabilizes the joint. Focusing on the quadriceps and hamstring groups helps absorb ground reaction forces, lessening the impact transferred to the cartilage surface. Stronger muscles distribute the load more evenly across the joint. Controlled resistance training reduces shear stress and shields existing tissue from excessive wear.
Nutritional Strategies for Cartilage Support
Dietary modifications and oral supplements provide raw materials and an anti-inflammatory environment to support the cartilage matrix. Omega-3 fatty acids, found in fatty fish like salmon, possess anti-inflammatory properties. These compounds help reduce levels of joint-damaging inflammatory markers, such as C-reactive protein.
Vitamin C is a water-soluble nutrient that functions as a cofactor in the synthesis of collagen, the main structural protein of cartilage. Adequate intake is necessary to form and stabilize new collagen molecules. Vitamin C’s antioxidant role helps neutralize reactive oxygen species, which contribute to oxidative stress and breakdown associated with joint degeneration.
Supplements like Glucosamine and Chondroitin are thought to provide building blocks for new cartilage and offer anti-inflammatory effects. While consensus on their effectiveness is mixed, some studies suggest they offer modest benefits for pain relief and functional improvement. Collagen supplements, specifically undenatured Type II collagen, have also shown positive results in reducing joint pain and stiffness.
Non-Surgical Injection Therapies
Physician-administered injections offer targeted, non-surgical intervention directly into the joint space. Viscosupplementation involves injecting hyaluronic acid (HA) into the knee. HA is a natural component of healthy joint fluid, and the goal is to restore the fluid’s viscoelasticity, improving lubrication and shock absorption. This treatment provides symptom relief for several months and may stimulate the body’s own HA production.
Platelet-Rich Plasma (PRP) therapy uses a concentration of a patient’s own platelets derived from a blood sample. After the blood is spun in a centrifuge, the plasma is rich in growth factors, such as Transforming Growth Factor-beta. When injected, these factors initiate a healing cascade, potentially stimulating new cartilage cells and promoting tissue regeneration. Evidence suggests PRP improves pain and function, especially in mild to moderate knee damage.
Corticosteroid injections are used primarily for rapid, short-term pain relief by delivering anti-inflammatory medication directly into the joint. These injections manage inflammation symptoms but do not contribute to cartilage repair or growth. Due to the risk of accelerating cartilage damage with repeated use, these injections are limited and are not a long-term solution.
Surgical Procedures Designed for Cartilage Repair
When non-surgical options are insufficient, specific procedures address localized cartilage defects by stimulating or replacing damaged tissue. Microfracture is a simple technique involving creating tiny holes in the bone beneath the defect. This causes blood and bone marrow cells, including mesenchymal stem cells, to seep out and form a clot that fills the defect. The primary limitation is that this process results in the formation of fibrocartilage, a repair tissue inferior to native hyaline cartilage that tends to wear down over time.
For small, contained defects, the Osteochondral Autograft Transfer System (OATS), or mosaicplasty, is a single-stage procedure. This technique involves harvesting plugs of healthy hyaline cartilage and underlying bone from a less weight-bearing area of the knee. These plugs are immediately transferred and implanted into the damaged site, replacing the defect with mature, native hyaline cartilage. The procedure is limited by the size of the defect, as it requires a suitable donor site.
The most advanced cell-based therapy is Autologous Chondrocyte Implantation (ACI), or its modern variation, Matrix-Induced ACI (MACI). This two-stage procedure begins with a small biopsy of healthy cartilage. The chondrocytes, the cells that produce cartilage, are multiplied in a laboratory over several weeks. During the second surgery, these expanded cells are implanted into the defect, often suspended on a collagen membrane. This method encourages the formation of hyaline-like cartilage, which is biomechanically superior to the fibrocartilage produced by microfracture, and is reserved for larger, isolated lesions.