Osteoarthritis of the joints What makes OA so special? We can help
NO. 8

Can Cartilage Heal?
Classic Research

Joints can only function well when the cartilage is healthy. That’s why one of the goals of osteoarthritis treatment is to heal the joint cartilage. But is it possible for cartilage to heal? For many years, there were only a few signs pointing to this possibility. A major study conducted in Canada and published in 1980 by Dr. Robert Salter and his team provided the first systematic results. In the following section, we describe the most important findings of this experimental study.

Cartilage Damage – an Injury Inside the Joint

  • Cartilage damage can have a  variety of causes. Accidents, many years of strain, and presumably also metabolic disorders can all contribute to cartilage damage. Full-thickness cartilage wounds even expose the bone underneath. This study only examined injuries of this kind that measured approximately 1 millimeter in diameter.

  • In treating these injuries, it is of utmost importance to protect the joints from further strain. The study compared the effects of complete immobilization (plaster cast), routine use and strain, and “movement without strain.” A newly-designed device allowed  the affected joints to move slowly and continuously without any application of muscle force, over a long period of time. This procedure completely eliminated the possibility of placing any strain on the joint.

  • To find out if the cartilage injury was actually healing researchers used various methods, including  direct observation of the joint’s surface (“had the cartilage injury completely disappeared?”). In addition, many microscopic and biochemical data were obtained. In the following pages, we will describe the healing processes that the researchers observed.

  • If cartilage wounds
    could be healed,
    this would
    one day be of
    great importance for
    the treatment of

    In What Phases Does Cartilage Heal, and How Does this Occur?

    • Early phase 
      In the full-thickness cartilage lesions (1 mm in diameter) that were examined in this study, new tissue growth was observed as the first sign of healing, soon after the injury occurred. As known from other injuries to the body, this new, young tissue quickly began to cover the base of the wound. This early phase shows nature’s efforts to close wounds again and heal them. This first phase lasted approximately two weeks. The young tissue that formed during this time was still very sensitive and vulnerable, however, and did not yet have the characteristics of healthy, durable cartilage.


    • Healing phase 
      After a few more weeks, researchers discovered an astounding fact: “Cartilage can heal completely!” In many lesions, the tissue continued to heal. The damaged areas gradually filled completely, the surface of the cartilage was soon fully closed, and it was no longer possible to see any damage with the naked eye. Even microscopic and biochemical investigations showed that this new tissue was increasingly identical to the normal, healthy cartilage around it. After a few weeks, the injury was no longer recognizable and was completely healed. 
      To their great surprise, however, the researchers found that this complete healing process only occurred with one method of treatment: namely “movement without strain.” All of the other treatment methods which were examined, including routine use and strain determined by the individual comfort level, showed significantly less progress towards healing.


    The results were as follows: 
    –  52% rate of healing when using movement without
    –  4% rate of healing in cases of routine use and strain
        based on the individual comfort level, or immobilization
        by a plaster cast.

    These results showed that “movement without strain” (or “continuous passive motion,” CPM) offered a significant advantage for the healing of cartilage lesions examined in this study. When this method of treatment was not used, signs of healing were extremely rare.

    An Important Rule

    These results showed that the hope for success in cartilage research is well founded. However, the study’s limitations must also be kept in mind. In this classic experimental study, researchers only examined a certain category of very small cartilage lesions (1 mm diameter, 4 mm average depth), in which the surrounding cartilage was completely healthy. Nevertheless, these results did have some immediate practical consequences:

    (1) Movement without strain supports cartilage healing.

    (2) Routine use and strain based on the patient’s own
          comfort level often causes additional damage to the
          injured cartilage. Instead, strain on the joint should
          be reduced by at least one third.

    (3) It takes time for cartilage to heal. These studies
          indicate that the healing process for cartilage
          damages takes several weeks. In general,
          patients should wait at least 12 weeks before
          slowly increasing the amount of strain placed
          on the injured joint.


    ► To continue with the next chapter, please click here



    MyAAS    HELP    Disclaimer    Legal & Privacy    About the American Arthritis Society