Knee pain from cartilage damage is a widespread issue, leading individuals to consider treatments from pain management to total knee replacement. Because traditional options have limitations, interest in regenerative medicine has grown. This field focuses on the body’s innate ability to heal, aiming to repair and regrow tissues like cartilage. It represents a shift from managing symptoms to potentially restoring the knee’s original structure and function.
The Challenge of Healing Knee Cartilage
Articular cartilage is the smooth, white tissue covering the ends of bones within a joint, acting as a shock absorber and allowing for fluid, painless movement. When damaged, this cartilage has a very limited capacity to heal on its own. The primary reason is its avascular nature; it lacks a direct blood supply and therefore does not receive the nutrients and restorative cells needed for repair.
Because of this limitation, cartilage injuries can worsen over time. The body’s natural response is to form a scar-like tissue called fibrocartilage. While this tissue can cover the defect, it is structurally inferior and less durable than the original hyaline cartilage, making the joint susceptible to future issues.
Cell-Based Therapies
Autologous Chondrocyte Implantation (ACI) is a two-stage surgical procedure that uses a patient’s own cells to grow new cartilage. First, a surgeon arthroscopically harvests a small piece of healthy cartilage from a non-weight-bearing area of the knee. These cartilage cells, called chondrocytes, are cultured and multiplied in a laboratory over several weeks. In the second surgery, the new cells are injected into the damaged area and covered by a patch.
A more advanced technique is Matrix-Induced Autologous Chondrocyte Implantation (MACI). This method also begins with harvesting chondrocytes, but the cells are seeded onto a biodegradable collagen scaffold in the lab. This cell-seeded membrane is then trimmed to the defect’s size and secured with fibrin glue during a single procedure. The scaffold provides a structural framework, supporting the cells as they develop into new cartilage.
The use of mesenchymal stem cells (MSCs) is another area of intense research. These cells are sourced from the patient’s own bone marrow or adipose (fat) tissue. When injected into the knee, MSCs may release signals that modulate inflammation and stimulate the body’s repair mechanisms. There is also the potential for these cells to differentiate directly into new cartilage cells, though this remains under clinical investigation.
Cartilage Transplant Techniques
Some regenerative procedures involve transplanting existing, healthy cartilage to repair a damaged area. One technique is Osteochondral Autograft Transplantation (OATS), also known as mosaicplasty. This surgery is for smaller cartilage defects and involves harvesting cylindrical plugs of healthy cartilage and underlying bone from a non-weight-bearing part of the patient’s knee. These plugs are then transferred and press-fit into the injury site, similar to moving sod plugs to a bare patch in a lawn.
When cartilage damage is too extensive for an autograft, a surgeon may use an Osteochondral Allograft Transplantation. This procedure is similar to OATS but uses a single, larger piece of cartilage and bone to repair the defect. The primary difference is that an allograft uses a precisely matched graft from a deceased donor. This allows for the reconstruction of significant defects that could not be filled with the patient’s own available tissue.
Injectable and Minimally Invasive Options
For patients seeking less invasive treatments, Platelet-Rich Plasma (PRP) therapy is a common option that uses healing components from a patient’s own blood. The process begins with a blood draw, and the blood is placed in a centrifuge to separate its components. This concentrates the platelets and growth factors into a small volume of plasma.
The resulting PRP solution is then injected directly into the knee joint. The injection delivers a high concentration of growth factors to the site of injury, which can help reduce inflammation and pain. These growth factors are believed to stimulate the joint environment and signal the body’s own repair cells to become more active. Research is still ongoing to determine the extent to which PRP can consistently regenerate new cartilage tissue.
Patient Suitability and Recovery Outlook
The success of surgical cartilage regeneration depends on careful patient selection. Ideal candidates for procedures like ACI or OATS are younger, active individuals with a specific, contained cartilage defect. These treatments are less suitable for patients with widespread, “bone-on-bone” arthritis where the damage is too diffuse. An evaluation, including an MRI, determines if the lesion’s size and location are appropriate for a regenerative procedure.
Recovery from these surgeries is a lengthy and demanding process. The initial phase involves a period of protected weight-bearing for six to eight weeks, requiring the patient to use crutches to avoid putting pressure on the healing graft. This is followed by months of intensive physical therapy aimed at restoring range of motion, strength, and function. A full return to high-impact sports can take from six months to over a year, highlighting that these advanced procedures are not quick fixes.