What is the Meniscus?
The meniscus is a C-shaped cushion of cartilage in the knee joint. When people talk about torn cartilage in the knee, they are usually referring to torn meniscus.
If a meniscus is so badly damaged it cannot be repaired, it may need to be removed or trimmed out. Without the meniscus cushion, persistent knee pain and arthritis may develop.
For many older patients with this condition, a knee joint replacement might be the best option. But active people, younger than 55, may be eligible for an alternative treatment: meniscal transplant surgery.
Why Meniscal Transplant Surgery?
A meniscal transplant replaces the damaged meniscus with donor cartilage.
If your meniscus is severely damaged or has been removed, it is likely that the articular cartilage protecting your knee will begin to wear. As this cartilage wears away, it becomes frayed and rough. Moving the bones along this exposed surface is painful. This condition is osteoarthritis.
The goal of meniscal transplant surgery is to replace the meniscus cushion before the articular cartilage is damaged. The donor cartilage supports and stabilizes the knee joint. This relieves knee pain. The hope is that the transplant will also delay the development of arthritis.
Where is the Meniscus?
Three bones meet to form your knee joint: your thighbone (femur), shinbone (tibia), and knee-cap (patella). Your patella sits in front of the joint to provide some protection.
The ends of your thighbone and shinbone are covered with articular cartilage. This slippery substance helps your knee bones glide smoothly across each other as you bend or straighten your leg. Two wedge-shaped pieces of meniscal cartilage act as "shock absorbers" between your thighbone and shinbone. Different from articular cartilage, the meniscus is tough and rubbery to help cushion and stabilize the joint. Each knee has two menisci, one on each side of the joint, the Lateral Meniscus and the Medial Meniscus.
Who May be a Candidate for Meniscal Transplant Surgery?
Most people with severe meniscal problems have also developed arthritis in the knee. If the articular cartilage has worn away too much, a meniscal transplant will not be helpful. The criteria for meniscal transplant may include:
- Younger than 55 years and physically active.
- Missing more than half of a meniscus as a result of previous surgery or injury, or a meniscus tear that cannot be repaired.
- Persistent activity-related pain.
- Knee with stable ligaments and normal alignment.
- None or minimal knee arthritis.
- Not obese.
Why do Meniscus Transplant Surgery?
The new meniscus can help with knee pain and possibly prevent future arthritis. The meniscus is an important structure for load transmission and shock absorption in the knee. The knee is subjected to up to 5 times body weight during activity, and half this force is transmitted through the meniscus with the knee straight, and 85% of the force goes through the meniscus with the knee bent ninety degrees.
Loss of the meniscus increases the pressure on the articular (gliding) cartilage, which eventually leads to degenerative changes. Pain may develop in the area after a significant portion of the meniscus has been removed. A successful meniscus allograft transplantation may be recommended for knee problems such as:
- Inability to play sports or other activities.
- Knee pain.
- Knee that gives way.
- Unstable knee.
- Persistent knee swelling.
The Surgical Procedure
Meniscal transplant surgery is an arthroscopic procedure. It can be performed on an outpatient basis. Knee arthroscopy is one of the most commonly performed surgical procedures. A miniature camera is inserted through a small incision. This provides a clear view of the inside of the knee. Your ortho-paedic surgeon inserts miniature surgical instruments through other small incisions to do the procedure.
Typically, a 2- to 4-inch incision is made in the knee with a few other small "poke" holes. The new meniscal tissue is anchored into the shinbone to stabilize the transplant. More sutures are placed into the meniscal transplant to secure it in place.
Allograft meniscus replacement can be safely performed under general or spinal anesthetic. In addition, local anesthetic is injected into the knee and the incisions. The patient is encouraged to discuss preferences with the anesthesiologist prior to surgery.
Post Operative Care
Allograft meniscus replacement is moderately painful.
The combination of narcotic and anti-inflammatory pain medication produces highly effective pain relief with minimal side effects. Good pain control is a balance between effectiveness and side ef-fects. Since all narcotic pain medicine can cause nausea and be constipating, drinking plenty of fluid and taking a stool softener after surgery can decrease these problems.
You will need to wear a knee brace and use crutches for the first 4 to 6 weeks after surgery. This gives the transplanted tissue time to become firmly attached to the bone.
Once the initial pain and swelling has settled down, physical therapy can begin. Specific exercises can restore range of motion and strength. Your exercise program focuses first on flexibility. Gentle stretches will improve your range of motion. As healing progresses, strengthening ex-ercises will gradually be added to your program.
Dr. Hayter will discuss with you when it is safe to return to work, as well as any sports activity.