Autologous chondrocyte transplantation (ACT) is a fairly new treatment method for deep (full-thickness) cartilage tears. Studies have only gathered long-term results for about the last 10 years. Since these types of tears are most common with soccer and football players they are the ones studied most often.

The ideas are the same for tennis players who often have to make quick stops or sudden turns. It's the mechanical load from movements like this that lead to cartilage injury or reinjury.

According to a recent study on high-level athletes returning to their sport, ACT worked best on younger players (less than 25 years old). The players who had other knee surgeries before ACT were less likely to have a good to excellent result.

Only 30 percent of the players who had ACT returned to their sport at their previous level. Eighty percent were the younger players with limited previous treatment. The ACT held up well under maximal mechanical forces imposed by frequent high-impact loads. Everyone was followed for at least one year. Some players still had good results up to four years later.