Degenerative Meniscus vs. Normal MeniscusAs people age, the strength of tissue changes. Just as skin gets wrinkles and hairs turn grey, a meniscus changes over time. The meniscus gets stiffer and weaker. When people in their 40s, 50s, and older sustain a torn meniscus, the meniscus tissue tends to be less healthy and less likely to heal, with or without surgery.
When meniscus tears occur in this setting, they are called degenerative meniscus tears. These tears look frayed. The meniscus tissue shows signs of age. Trying to surgically repair this type of meniscus tear is like trying to sew together frayed fabric -- the tissue simply would not hold together.
On the other hand, younger, healthier meniscus tissue, seen in people in their teens and 20s, tends to tear more cleanly. The tissue is rubbery and strong, and when it tears, it tends to do so without frayed edges. It also tends to tear in a single line, rather than in multiple directions. These types of tears may be amenable to a surgical repair.
Meniscus Blood SupplyIn younger individuals, the meniscus tissue is healthy, but still may not have an ability to heal. The meniscus is a round piece of cartilage that is attached to the knee joint from its periphery (the outer edge). The blood supply to the outer edge of the meniscus is good, but there is little blood that gets to the central part of the meniscus. Therefore, tears extending into the center of the meniscus also have a poor ability to heal, with or without surgery.
Stability of a TearThe last important factor to determine if a meniscus tear can heal is if the tear is stable. A partial tear of the meniscus (that does not go all the way through the meniscus) is stable. A deeper tear that extends all the way through the meniscus is unstable, and even if there is healthy tissue and a good blood supply, will be unable to heal. Unstable tears tend to pull apart before any significant healing occurs.
Surgery can be used to stabilize some tears of the meniscus. If the torn meniscus is healthy tissue, with a good blood supply, then surgery to stabilize the tear may allow for healing.
Is Surgery Necessary?In summary, in order for a meniscus tear to heal, it must have the following attributes:
- Healthy tissue
- Good blood supply
That said, many people have meniscus tears that will improve with some simpler treatments. Often, a degenerative meniscus tear will have symptoms that subside over time and never require surgery. Deciding when surgery is necessary is not simply a question of if there is a tear, but it must take into account all of these factors that determine if a meniscus tear can heal.
Greis PE, et al. "Meniscal Injury: II. Management" J. Am. Acad. Ortho. Surg., May/June 2002; 10: 177 - 187.