by: Kathleen A. Hogan, MD
Watching football on Sunday afternoon, your favorite player twists their knee and lays on the ground. Have they torn a ligament or meniscus? Or will they be back playing later in the game? What impact do knee injuries have on the eventual development of osteoarthritis?
Many Factors Influence Arthritis Development
The development of arthritis is multifactorial. Body weight, leg alignment, and genetic factors all influence the eventual breakdown of joint cartilage. Injuries certainly play a role as well.
Intra-articular fractures which directly damage the joint surface, are the most extreme examples of an injury which has a known increase in the development of arthritis. Even when the pieces are carefully put back in place and fixed with plates and screws, once broken the joint cartilage will never quite be the same.
Injuries to the Meniscus and Ligaments
What about sports injuries to meniscus and ligaments? The meniscus is a crescent shaped, fibro-cartilage structure that is found on the inner and outer side of the knee joint. It helps to dissipate friction and weight bearing forces arcross the knee joint, protecting the articular cartilage. Before the importance of the meniscius was recognized, the treatment for a torn meniscus was to remove it in its entirety. Unfortunately, arthritis often developed many years later. Forty years after a total meniscectomy as a teenager, patients were 4 times more likely to have developed symptomatic arthritis in that knee compared to the non operated knee.
Today, surgeons try to preserve the meniscus as best possible. In younger patients, meniscus repair is sometimes possible. In older patients, only the torn portion of the meniscus is removed. However, the same forces that damaged the meniscus may have also damaged the cartilage of the knee. In one study, 43% of patients (average age 49) undergoing surgery for a torn meniscus were found to have damage to the articular cartilage of the knee, damage that was graded as severe in half of those cases.
Anterior Cruciate Ligament (ACL) Repair
The anterior cruciate ligament (ACL) functions to keep the tibia balanced under the femur during rotational motions. The forces generated during rupture of the ligament often damage the articular cartilage of the knee. Repair of the ligament helps to prevent instability and it is theorized that this protects cartilage from further injury. The type of surgical repair, concurrent meniscus injuries, and patient activity may all influence the development of later arthritis. One Swedish study found a 10% incidence of post traumatic arthritis of the knee 10 years after injury. Other studies have found a much higher rate of arthritis.
Knee Injuries Influence Development of Arthritis
Knee injuries certainly do influence the development of arthritis. A prospective study of 1321 medical students followed for 22 years found that a knee injury as a young adult increased the incidence of knee arthritis from 6% to 13% at age 65. The risk in high performance athletes is likely higher. A retrospective review of athletes at the NFL Combine who had undergone MRI to evaluate prior injuries found evidence of early arthritis in 11% of those with meniscus repair, 24% with ACL repair, and 27% with partial menisectomy!
Preventing Further Injury
Although techniques of repairing damaged articular cartilage, meniscus, and ligaments are improving, injury prevention is the best way to limit cartilage damage in the knee from sports. If you have had a significant injury to your knee in the past, your risk of developing arthritis in that knee is certainly higher, but not inevitable. Just because X-rays may show arthritis, this does not mean that you will require joint replacement surgery. Minimizing further damage by keeping your legs muscles strong, your joints flexible, and your weight within a normal range are very important if you have had prior knee injuries.