Knee Cartilage Replacement

Knee arthritis is a condition that causes damage to our joints and the cartilage that helps the knees to function normally. Once that damage has occurred, we are often told that there is nothing that can be done to turn back the clock—you can't replace worn-out cartilage. However, medicine is getting better at tackling cartilage problems, and perhaps we are getting closer to a solution where we can turn back the clock on arthritis.

A doctor examining his patients knee

Knee Arthritis

Many patients with knee arthritis want a solution to their problem other than artificial joint replacement surgery. Arthritis causes joint problems because of the loss of cartilage within the knee. This leads to the typical symptoms of arthritis including:

  • Inflammation
  • Swelling
  • Knee pain

These symptoms of knee arthritis tend to worsen as arthritis progresses. Therefore, the logical conclusion would be to simply replace the worn-out cartilage with new cartilage.

Problems With Replacing Worn Cartilage

Unfortunately, a cartilage replacement procedure is not as simple a task as we would hope. Cartilage cells can be cloned and reproduced in a lab. The real problem comes up when we want to place those cells in a particular location and get them to function effectively in that area. Cartilage is a complex tissue; in order for cartilage to function, it must be able to withstand tremendous forces. Simply injecting cartilage into a joint would serve no useful purpose, those cells would be destroyed in a short time.

The problem is that no one has been able to figure out a way for the body to accept new cartilage and allow the cartilage to adhere to the surface of the joint. Once on the joint surface, the cartilage must be able to support the weight of the body and glide smoothly to allow normal movements. Many scientists are working on ways to accomplish these goals, but there is no solution right now.

Growing Cartilage in the Lab

There are surgical procedures that use cartilage cells that have been harvested from a patient, cloned and reproduced in a lab, and then reinserted into the patient. However, these cartilage cells can only be inserted into relatively small voids in the cartilage, not to "resurface" a worn out, arthritic joint.

There are possible solutions for patients with a limited area of cartilage damage, but this is not an arthritis treatment. These cartilage replacement techniques are for patients with limited areas of cartilage damage, often caused by sports or traumatic injuries.

For replacement to succeed, areas of cartilage damage have to be small—not the widespread damage seen in arthritis.

How Cartilage Replacement Can Work

In order for cartilage replacement to become a reality, a few basic problems must be resolved.

  • Scaffold: Cartilage is more than just cells. Cartilage is a tissue made up mostly of non-cellular material including water, collagen, and other proteins. Injecting cartilage cells into the knee does not address the other components of cartilage that also need to be in place.
  • Adherence: Cartilage forms a thin lining on the end of the bone. Finding a way for cartilage to adhere to the bone is difficult.
  • Joint Damage: As knee arthritis progresses, the joint becomes further damaged over time. This damage includes the formation of bone spurs, the flattening of the normally rounded ends of the bone, and changes in the alignment of the joint. These changes make restoring a joint impossible even if cartilage replacement were a possibility.

Thousands of scientists and research physicians are trying to address this problem of how to develop a cartilage replacement for knee arthritis patients. While there are surgical procedures for cartilage replacement in patients with limited areas of damage, there is no procedure for cartilage replacement in knee arthritis. There certainly has been progress, and we are closer to a solution right now than we were a few years ago, but there is no cartilage replacement procedure presently available for knee arthritis patients.

Future research is looking into solutions that involve the use of growth factors and genetic engineering to direct the body to repair cartilage.

The body does a poor job of repairing cartilage damage on its own, and future research is directed at being able to manipulate the body to repair the damage before arthritis destroys the joint.

A Word From Verywell

Ultimately, there may be a treatment for knee cartilage damage where we can restore, replace, or regrow the worn-out surface of our joints, however, we clearly are not there yet. There are some very specific situations where cartilage restoration is currently a viable treatment, but for the vast majority of people, their cartilage damage cannot be undone, at least not yet. Perhaps in the coming decades, that will change, but for now, cartilage regeneration is more a subject of research than mainstream treatment.

4 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. Lespasio MJ, Piuzzi NS, Husni ME, Muschler GF, Guarino A, Mont MA. Knee Osteoarthritis: A Primer. Perm J. 2017;21:16-183. doi:10.7812/TPP/16-183

  2. Zhang L, Hu J, Athanasiou KA. The role of tissue engineering in articular cartilage repair and regeneration. Crit Rev Biomed Eng. 2009;37(1-2):1-57.

  3. Shin CS, Lee JH. Arthroscopic Treatment for Osteoarthritic KneeKnee Surgery & Related Research. 2012;24(4):187-192. doi:10.5792/ksrr.2012.24.4.187

  4. Welton KL, Logterman S, Bartley JH, Vidal AF, Mccarty EC. Knee Cartilage Repair and Restoration: Common Problems and Solutions. Clin Sports Med. 2018;37(2):307-330. doi:10.1016/j.csm.2017.12.008

Additional Reading
  • "Questions About Stem Cells" American Academy of Orthopedic Surgeons. September 2007.

By Jonathan Cluett, MD
Jonathan Cluett, MD, is board-certified in orthopedic surgery. He served as assistant team physician to Chivas USA (Major League Soccer) and the United States men's and women's national soccer teams.