The knee is a complex joint that must support the weight of the body while allowing the leg to bend freely. An important part of the knee joint is the meniscus. The meniscus is a fibrous cartilage structure that acts as a shock absorber. While these menisci perform very well during various strenuous activities, they can and do tear. In fact, a torn meniscus in the knee is one of the most common orthopedic injuries.
A torn meniscus of the knee often causes pain and swelling in the knee. Patients with a torn meniscus cannot squat or kneel, and the knee joint does not move smoothly. In fact, many patients with a torn meniscus describe the joint as popping, locking, catching or even “giving out.”
The meniscus of the knee can be torn in several ways; however, most torn menisci result from either one of two things: athletic activity or degenerative arthritis. As you would imagine, menisci torn during sport occur more commonly in young athletes such as dancers, certain kinds of track and field athletes, and basketball, soccer and football players. People with degenerative arthritis tend to be older and often have careers that require a lot of bending at the knee, such as carpet layers, carpenters, plumbers, etc.
Some people can live with small tears in their knee meniscus, but many people ultimately require surgery to fix the problem. One of the major approaches is to perform a total or partial meniscectomy of the damaged knee meniscus. Generally speaking, surgeons offer partial meniscectomy because patients heal faster, and results are about as good as a total meniscectomy. Unfortunately, surgical repair of these tissues is not always successful, especially in older individuals with tears related to degenerative arthritis. Consequently, surgical researchers are keen to discover new ways to improve partial meniscectomy to help people with meniscal tears of the knee.
One exciting option is using stem cells to potentially help patients regrow healthy meniscus after surgeons remove the damaged portion.
In one study, orthopedic surgeons at various surgical centers around the United States participated in an I/II, randomized, double-blind, controlled study to study the effects of human mesenchymal stem cells in people with a meniscal tear of the knee. Researchers recruited 60 patients who were eligible to receive a partial meniscectomy and sorted them into three groups: treatment group A received 50 million human mesenchymal stem cells, group B received 150 million stem cells, and group C (the control group) simply received an infusion of salt water. Patients received an injection of stem cells into the knee, 7 to 10 days after their partial meniscectomy surgery. Then researchers followed the patients for six weeks, six months, one year, and two years after the procedure.
Researchers found that some patients who received human mesenchymal stem cells had a significant increase in the size of their menisci after surgery. By contrast, no single patient in the control group had an increase in the size of their menisci. In other words, stem cells were found to be able to increase the size of the knee meniscus in some patients, as originally hypothesized. Likewise, the study authors could find no clinically important safety issues from injecting stem cells into the knees of patients. Perhaps most importantly, people who received mesenchymal stem cells reported a significant reduction in the amount of pain they experienced due to degenerative changes in the knee. In other words, partial meniscectomy plus stem cells apparently helped patients with degenerative arthritis of the knee.
The authors concluded that this research shows that human mesenchymal stem cells have the potential to be able to repair knee meniscus tissue and improve knee pain in people with meniscal tears. While additional research is needed, these results are very exciting for people who have torn menisci, especially older patients whose knee pain is a result of osteoarthritis or degenerative joint disease in the knee.