Meniscus Allograft Replacement Surgery

Meniscus Allograft Replacement Surgery: A minimally invasive method to restore previously removed torn knee cartilage with cadaver tissue

Edited By John R. Trey Green III, M.D., Associate Professor, UW Orthopaedics & Sports Medicine John R. Trey Green III, M.D.

Last updated: December 31, 2009


Meniscus allograft replacement surgery is a minimally invasive method to restore previously removed torn knee cartilage with cadaver tissue. The new meniscus is sewn in place and requires postoperative protection to allow healing. Physical therapy is useful to regain full function of the knee, which occurs on average 6 months after surgery.

Symptoms & Diagnosis

Characteristics of meniscus tear

A torn meniscus generally produces pain in the region of the tear and swelling in the knee joint. These symptoms are made worse with pivoting motions, squatting, and vigorous activities. Torn meniscus fragments can get caught in the knee joint and cause catching sensations. If a large enough fragment becomes lodged between the bearing surfaces, the knee may ‘lock’ and become unable to be fully bent or extended. Since most meniscus tears are not repairable, they require removal of meniscus tissue (meniscectomy). The loss of meniscus cushioning overloads the articular (gliding surface) cartilage leading to the development of arthritis over the ensuing decades. A few patients experience pain in the region of the removed cartilage prior to the development of arthritic changes. This small group may benefit from allograft meniscus surgery.


Meniscus tears are described by the tear pattern. Tears occur in either the horizontal or vertical direction, or a combination of both. Although the goal of meniscus surgery is to preserve healthy meniscus tissue, many types of tears are not repairable. A meniscus tear requires a blood supply to heal, and since only the peripheral third of the meniscus has it, repairs are generally limited to the peripheral region. Please see arthroscopic meniscectomy, and arthroscopic meniscus repair for more information.

Similar conditions

Injuries to the articular (gliding surface) cartilage can also cause pain, swelling and catching symptoms in the knee. An experienced surgeon can often distinguish between the two conditions with a thorough history and physical exam, but MRI can be useful as well. These two conditions can occur together and are most accurately diagnosed by arthroscopy. Please see articular cartilage injuries for more information.

Incidence and risk factors

Meniscus tears are common in active participants of sports, which require cutting and pivoting. In the United States, there are an estimated 850,000 meniscus surgeries performed each year, the vast majority being meniscus removal (meniscectomy) operations. The meniscus on the side closest to the other knee (medial) is torn more frequently, and men injure their meniscus more often than women.


A torn meniscus is diagnosed with a thorough history and physical exam. Traumatic meniscus tears often occur with twisting type or hyper-flexion injuries. Physical exam maneuvers that reproduce these symptoms may include squatting and rotational manipulations. MRI is useful to confirm the diagnosis, but the most accurate test is diagnostic arthroscopy. The short term results from menisectomy and meniscus repair are good, but a few patients who have had significant portions of their meniscus removed, develop pain in the local area. X-rays are important to make sure that arthritis has not yet developed, since meniscus replacement is not effective once advanced degenerative changes are present.



Anti-inflammatory medications, taken by mouth or injected directly into the knee, can be useful to reduce the pain and swelling symptoms associated with meniscus tears, but do not improve healing. No medications or nutritional supplements have been scientifically documented as beneficial for meniscus healing.


Quadriceps strengthening exercises are useful to reduce swelling and restore normal muscular control to an injured knee. They useful to reduce symptoms and speed rehabilitation.

Possible benefits of allograft meniscus replacement surgery

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 replacement restores the cushioning meniscus tissue, relieving this pain.

Types of surgery recommended

Arthroscopic surgery is recommended for meniscus tears. The basic principle of meniscus surgery is preservation of healthy meniscus. Since meniscus repair is only feasible in the peripheral area of meniscus that has adequate blood supply, most meniscus tears are treated with arthroscopic meniscectomy. Some patients experience activity related pain in the region where a significant portion of meniscus has been removed. In many patients, there is a window of time after the development of this pain, and before the onset of arthritis, when meniscus replacement surgery can be effective.

Who should consider allograft meniscus replacement surgery?

Meniscus replacement is considered when:

  • the patient is healthy and wishes to remain active,
  • the patient understands the rehabilitation, and accepts the risks of surgery,
  • the patient experiences pain located in the same area, from which a significant portion of meniscus has previously been removed no less than six months prior,
  • the patient is not overweight,
  • the patient is skeletally mature and less than 50 years old,
  • the knee alignment is normal with stable ligaments
  • the knee does not have significant injury to the articular (gliding surface) cartilage or evidence of arthritis on x-rays, and
  • the surgeon is experienced in meniscus replacement

What happens without surgery?

Unfortunately, most patients who have significant portions of their meniscus removed develop arthritis over the ensuing decades. A few of these patients develop activity related pain in the region of meniscus removal prior to the development of arthritis. These patients have an opportunity for allograft meniscus replacement surgery. The window of opportunity will close when arthritis develops, and the opportunity for allograft meniscus replacement will be lost. The time for arthritis to develop is highly variable and unpredictable.

Surgical options

Meniscus tears can be treated by meniscus removal (meniscectomy), meniscus repair, or in unusual circumstances, meniscus replacement. Since the goal of surgery is to preserve healthy meniscus, meniscus repair is attempted when the tear is repairable.
The simplest operation is meniscectomy, removing the damaged meniscus tissue. This has good short term results but leads to the development of arthritis ten to twenty years later. Meniscus repair also has good results, but has a longer recovery time than meniscectomy and is limited to tears, which are amenable to repair. Meniscus replacement is considered for young, active patients who have previously had most of their meniscus removed, and develop pain in the area without having advanced degenerative changes to the articular (gliding surface) cartilage. Please see meniscectomy and meniscus repair for additional information.


In the hands of an experienced surgeon, meniscus allograft replacement is an effective operation to restore comfort and function to the knee of a well-motivated patient. Using the technique described below, meniscus healing is about 90%. Short term outcomes are good, but the long term benefits are still unknown, since the procedure is still relatively new.


Surgery for pain following significant meniscus removal is not an emergency. It is reserved for at least six months following meniscectomy. Arthroscopic meniscus replacement is an elective procedure that can be scheduled to minimize disruption of patients’ lives. The window of opportunity will close when arthritis develops, and the opportunity for allograft meniscus replacement will be lost. The time for arthritis to develop is highly variable and unpredictable.


All surgery has risks. There is likely nothing you could imagine could go wrong that has not gone wrong at some time. That being said, meniscus

replacement is a safe procedure with a complication rate of 1.3%. The most common complications are injuries to skin nerves, the vast majority of which resolve without additional procedures by three months post surgery. Injury to larger nerves or blood vessels is rare, as are blood clots. Knee stiffness, infections, and other problems are uncommon, but can occur. An experienced surgical team uses special techniques to minimize these risks, but unfortunately they cannot be completely eliminated.

Managing risk

The most effective treatment of complications is prevention. For example, the risk of infection is decreased by giving antibiotics prior to surgery, and the risk of blood clots is decreased by using anti-embolism stockings. If infection does occur, repeat arthroscopy to remove infected tissue and debris, in conjunction with antibiotics for six weeks is generally effective. If blood clots occur, blood thinners are used for three months to decrease the chance of clots growing or breaking off and traveling to the lungs. Knee stiffness can often be managed with physical therapy and braces, but may require arthroscopic releases to restore motion. Since most complications can be effectively managed when identified promptly, if patients have questions or concerns about the post-operative course, the surgeon should be informed as soon as possible.


Since allograft meniscus replacement is an elective procedure, the patient’s situation can be optimized for successful surgery. There should be someone to help at home for the first several days since mobility will be impaired. There should be no current infections. The knee should have no sores or scratches. The knee should not be shaved on the day of surgery or the day preceding surgery. Cutting down or stopping smoking will decrease risk of infection and blood clots, and improve healing. Airplane flights should not be scheduled within the first five days following surgery to decrease chances of blood clots. Dental work often releases bacteria into the blood, so should not be scheduled in the first six weeks after surgery. If unavoidable, antibiotics around the time of the dental work may decrease infection risk.


Arthroscopic meniscus replacement is an elective procedure that can be scheduled to minimize disruption of patients’ lives. The window of opportunity will close when arthritis develops, and the opportunity for allograft meniscus replacement will be lost. The time for arthritis to develop is highly variable and unpredictable, but is not generally over days and weeks, but more commonly over years.


The surgeon’s office should provide a reasonable estimate of the surgeon’s fees, the hospital fee, the anesthesia fee, and the degree to which these should be covered by the patients insurance.

Surgical team

Arthroscopic meniscus replacement is an advanced surgical skill that should be performed by an orthopedic surgeon trained in advanced arthroscopic techniques. The surgery should be performed in a hospital or outpatient surgical center that handles a large volume of arthroscopic knee surgeries.

Finding an experienced surgeon

Surgeons who have had fellowship training in sports medicine have received additional advanced training in arthroscopic techniques such as meniscus replacement. The operation is best performed by a surgeon with an interest and experience in arthroscopic meniscus replacement. Surgeons with these qualifications can be located through university schools of medicine, and are often members of specialty societies such as the American Orthopedic Society for Sports Medicine and Arthroscopy Association of North America.


Arthroscopic meniscus repair is an outpatient surgery that is performed in a hospital or outpatient surgical center. A center that handles a large volume of arthroscopic knee surgeries has experienced nurses and therapists to assist patients recover.

Technical details

After the anesthetic is administered and knee examined, a tourniquet is placed on the upper thigh and the thigh is secured to the table in a padded limb holder. The knee and lower leg are cleansed and draped and a diagnostic arthroscopy is performed. A diagnostic arthroscopy is a thorough examination of the inside of the joint with a camera hooked up to viewing screens. The instruments are approximately 5mm in diameter and are inserted through three or four 1cm incisions around the knee. One incision is for sterile saline inflow, used to improve visualization within the joint. A systematic inspection of the knee documents any other problems, which can also be addressed. An inspection of the gliding surfaces in the region of the previously removed meniscus is important to make sure arthritic changes have not yet become advanced enough to preclude the allograft meniscus replacement. The remainder of the meniscus is removed with arthroscopic instruments. A two to three inch vertical incision is made, and a trough cut into the tibia (shin bone) where the native meniscus attached. A cadaver (allograft) meniscus, of the appropriate size from radiographic measurements, is prepared with a similarly sized bone bridge connecting the front and back meniscus attachments to bone. The new meniscus is press fit into the bone trough and is secured into the trough as necessary with suture or absorbable pins. The periphery of the meniscus is then repaired to the adjacent joint capsule with sutures similar to a meniscus repair.


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.

Length of allograft meniscus replacement surgery

Allograft meniscus replacement generally takes between an hour and a half and two hours. Depending on how much other surgery is necessary to take care of other problems in the knee, the time may be a bit more or less.

Pain and pain management

Allograftmeniscus replacement is moderately painful. Because a bone trough and an open incision is performed, it is more painful than a standard arthroscopy, and comparable to a ligament reconstruction or another procedure that requires drilling holes through the bone. Local anesthetic is used during surgery to minimize pain, but patients generally have a swollen, painful knee for the first four to five days after surgery, which is manageable with oral narcotic and anti-inflammatory pain medication.

Use of medications

Oral anti-inflammatory medication is taken by mouth on a schedule, and narcotic pain medicine is taken by mouth as needed. Patients require narcotic pain medications an average of 4-7 days after surgery.

Effectiveness of medications

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 effects. 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.

Important side effects

Narcotic pain medications can cause drowsiness, slowness of breathing, difficulty emptying the bladder and bowel, nausea, vomiting and allergic reactions. Patients who have substantial narcotic medications or alcohol in the recent past may find that usual doses of pain medication are less effective. For some patients, balancing the benefit and the side effects of pain medication is challenging. Patients should notify their surgeon if they have had previous difficulties with pain medication or pain control.

Hospital stay

Allograft meniscus replacement is an outpatient procedure. After surgery, the patient spends one to two hours in the recovery room, and is discharged to home with a friend or family member.

Hospital discharge

After allograft meniscus replacement, the patient generally has a cryocuff and a knee brace. The cryocuff is cold, compression device, that consists of a bladder around the knee and a cooler for ice a water. Using gravity to empty and fill the bladder, the knee can be kept cool to minimize swelling and decrease pain. The brace keeps the leg straight. Generally, full weight-bearing in the brace may be permitted immediately after surgery. Taking it easy the first two days after surgery, with the limb propped up when sitting helps keep swelling to a minimum, and will actually speed recovery. During this time, pumping the ankle up and down is recommended to improve blood flow in the leg. Specific post operative instructions will be reviewed prior to discharge.

Convalescent assistance

Even though patients go home after allograft meniscus replacement, they will appreciate some assistance for the first several days after surgery. Driving is not recommended until a patient is comfortable off all narcotic pain medications.

Physical therapy

The three early postoperative rehabilitation goals are; get the knee out fully straight, decrease swelling, and regain quadriceps muscle control. Patients are encouraged to do straight leg raises in the brace immediately after surgery. The brace is used to walk with the knee in extension for six weeks. Range of motion is generally started soon after surgery from 0-90 degrees, without any weight-bearing during motion. The brace is unlocked at six weeks and weaned off after eight weeks when good quadriceps control is demonstrated. Motion is increased as tolerated at six weeks, but deep squats are avoided until 12 weeks. Low impact type activities such as swimming and exercise machines are encouraged at 12 weeks, with advancement to cutting and pivoting sports generally at 16 weeks. The assistance of a physical therapist is very helpful in achieving a rapid full recovery.

Rehabilitation options

Sports Medicine Clinic has experienced physical therapists, who regularly guide patients through meniscus surgery rehabilitation. Since much of the work of rehabilitation is done at home, the surgeon, patient and therapist are partners in a successful outcome. Since many patients come a distance for our expertise, we have developed working relationships with many therapy clinics in the surrounding area to make therapy more convenient.

Usual response

Patients are generally satisfied with the progress made during rehabilitation, and often feel ready to do more than allowed during each phase. Adherence to this protocol has led to successful outcome. If the exercises seem particularly difficult or painful, the patient should contact the therapist or surgeon.


This is a safe rehabilitation program with minimal risk.

Duration of rehabilitation

Return to sports requires the ability to perform sports specific drills at competition speed. Depending on the rigors of the sport, the preoperative condition, associated injuries, and other individual factors, return to a chosen sport generally takes about 6 months. Rehabilitation should continue until the patient’s athletic goals are achieved.

Returning to ordinary daily activities

Patients are generally able to get back to activities of daily living a week after allograft meniscus replacement. These activities will initially be performed while wearing a brace. Help at home for the first several days after surgery is beneficial.

Long-term patient limitations

After full rehabilitation and recovery, patients have no limitations. However, if significant articular (gliding) cartilage injury or degeneration is noted at the time of diagnostic arthroscopy, high impact type sports are discouraged to slow the progression of arthritis.


Since much of the rehabilitation is done at home, rehabilitation is cost-effective. The surgeon and therapist should be able to provide the usual cost of the rehabilitation program.

Summary of allograft meniscus replacement surgery for meniscus tear

Meniscus allograft replacement surgery is a minimally invasive method to restore previously removed torn knee cartilage with cadaver tissue. The new meniscus is sewn in place and requires postoperative protection to allow healing. Physical therapy is useful to regain full function of the knee, which occurs on average 6 months after surgery.