Meniscus transplant or replacement surgery is considered for patients with persistent knee pain, and swelling which occured after previous surgery to remove a torn meniscus. The meniscus is very important to preserve cushioning within the knee joint. Meniscus tears are very common and can cause arthritis. Young, active patients may notice knee pain and swelling when they try to return to sports after a partial menisectomy. One possible treatment alternative in this situation is an allograft meniscus transplantation.
Common questions about the meniscus:
- Do you need a meniscus?
- Can I walk without a meniscus?
- Can you replace a meniscus?
Function of the meniscus
“Do I need a meniscus?”: This is a very common question. The answer is yes, the meniscus is critical to a well functioning knee.
Each knee has two menisci. The medial and the lateral meniscus. A meniscus serves a very important function as a shock absorber. The meniscus absorbs about 50% of the impact of your activities. As you can see in the image to below, when we step, the meniscus absorbs the force of walking. The meniscus diminishes the stress that the bones of the knee experience during walking, sports and other activities. Osteoarthritis, or degeneration of the knee may develop after surgery to remove a meniscus tear because of the loss of this cushioning effect. The meniscus has a role in the stability of the knee as well. In people with an ACL tear and a meniscus tear, they will have a much higher chance of having an unstable knee after their injury.
Persistent pain after meniscus surgery
Some patients have persistent knee pain and swelling develop after meniscus tear surgery. Meniscus tears are very common. A very common surgery to treat meniscus tears is called an arthroscopic partial meniscectomy. During a partial menisectomy the surgeon will remove the torn portion of the meniscus. Because the meniscus is an important shock absorber, as soon as a part of the meniscus is removed, osteoarthritis may start to develop. Osteoarthritis will cause the “articular” cartilage on the ends of your bone to deteriorate. This process can lead to pain with sports, and eventually pain with walking, and even at rest. Arthritis is also an inflammatory process, so you may find that you develop swelling with activities after surgery to remove a portion of your meniscus.
Can you replace the meniscus?
After meniscus surgery some of you will develop persistent pain and swelling in the knee. That pain and swelling might indicate that the knee has started to deteriorate, and the arthritic process has initiated. If the pain and swelling persist, despite medications, physical therapy, time, and other non-surgical options then some patients may be told they may consider meniscus replacement or transplantation as an option.
Am I a candidate for a meniscus transplant?
In order to improve your chance of success after a meniscus transplant, and to minimize the risk of failure or complications we use the following criteria as a rough guide:
- Younger than age 55
- You had prior surgery to remove a portion of your meniscus
- There is significant pain and swelling with activity
- There is minimal arthritis, or none at all.
- You are not obese.
How is a meniscus transplantation performed?
Planning. In the office we will obtain x-rays to look at the “alignment” of your knee. If you are bow legged (varus) or knock- kneed (valgus) then we may need to consider additional procedures to correct this. Poor alignment might put the new meniscus at an unacceptably high risk for failure. An X-ray and an MRI will show how much of your meniscus was removed during your previous surgery. It will also show whether or not you have developed arthritic changes. When we are trying to decide if a meniscus transplant is an option for you we will be looking to be sure that you do not have advanced arthritis, deformity of the bone or large bone spurs. Severe arthritis, and bone spurs will make could result in failure of the meniscus transplant.
During a meniscus transplant surgery we will perform an arthroscopy to inspect the knee joint. We need to be sure that the arthritis is not too severe. We also need to be sure that there are no other issues within the knee that need to be addressed at the same time. After the arthroscopy is performed we then begin work to place the new meniscus into the knee. This is one of the most technically challenging procedures that a sports medicine surgeon will perform. Proper placement and proper suturing of the meniscus improves the chance of success after a meniscus replacement.
When we are preparing to start the replacement we need to find the “roots” or the attachment points for the meniscus in your knee. Once the roots are identified then we determine where will are going to place the new meniscus. If we are transplanting the lateral or outer meniscus then we will make a trough in the bone. That trough will ultimately hold the meniscus in place. If we are transplanting the medial meniscus then we usually use small bone tunnels to hold the root attachment of your new meniscus in place.
Once the trough or tunnels are created the new meniscus is placed into your knee through an open incision. The meniscus is then repaired with stitches to complete the transplant.
On occasion we will also need to reconstruct the ACL or the PCL ligament(s) at the same time as the meniscus replacement. If you had an ACL or a PCL tear which created instability of the knee then having the ligament reconstructed at the same time as the transplant will improve the likelihood that the new meniscus will heal.
Do meniscus transplants work — Are they successful?
Many meniscus transplants are successful and alleviate or at least minimize the pain and swelling of a deteriorating knee due to the loss of a meniscus. Proper patient selection is critical. Not all people who have pain due to a previous meniscus tear will be a candidate for a meniscus transplant. If the arthritis is too severe, or if the bones are deformed due to arthritis then the meniscus replacement has a significant risk of failure. The success rates for a transplant varies. Many scientific papers will quote success rates for a meniscus allograft transplant (MAT) in a range of 70-85%.
Recovery from a meniscus transplant
Like any surgery, complications can occur. Complications after a meniscus transplant are rare, but the risk of complications is never zero.
- Stiffness of the knee
- Part of the meniscus doesn’t heal.
- Damage to nerves around the knee.
- Anesthetic complications
- Blood clots in the leg.
- Getting an infection from the new meniscus (very rare).
- incomplete or no pain relief.
- need for more surgery
The recovery after a meniscus transplant will be long. Most surgeons will not allow their patients to go back to sports for 8-12 months following surgery. Some surgeons may not allow someone to go back to sports after a transplant. This remains a controversial topic. The reason for the controversy is that the new meniscus is an allograft… which means that it is from a cadaver. There are no living cells within the meniscus and we do not know if that will affect how long the new meniscus will last. This is a big operation… you do not want to put the new meniscus at risk by returning to intense heavy sport participation.
If the surgery also involved a reconstruction of the ACL or the PCL then the recovery will extend beyond one year before being allowed to return to sports.
What is the function of the meniscus?
Knee pain after meniscus surgery
Recovery from meniscus tear surgery
Success rates for meniscus transplants
Meniscus transplant vs physical therapy for knee pain after meniscus surgery.