Meniscus Transplantation

Meniscus Transplantation

Samuel P. Robinson

Kevin F. Bonner

The function of the meniscus in load sharing, shock absorption, joint stability, joint nutrition, and overall protection of the articular cartilage is well known (Fig. 58.1) (1, 2 and 3). As a result of our increased understanding of meniscus function, the treatment of meniscal injuries has evolved from complete resection to meniscal preservation when possible. Although meniscus preservation through repair or limited resection is always preferable, specific meniscal pathology often dictates treatment. Relatively large resections to include subtotal or total meniscectomy are not uncommon, even in young patients.

Articular contact stresses increase as a function of the amount of meniscus resected. Complete medial meniscectomy decreases contact area by 50% to 70% and doubles the joint contact stress of the medial compartment (4). Segmental meniscectomy may have a similar effect on contact area and contact stress when compared with complete meniscectomy (5). Complete lateral meniscectomy decreases contact area 40% to 50% and increases joint contact stress 200% to 300% in part due to the relative convexity of the lateral tibial condyle (4). For this reason, lateral menisectomy is considered to have a poorer prognosis than medial menisectomy with regard to the development of osteoarthritis and pain. Since the medial meniscus is also the primary secondary stabilizer to anterior tibial translation in an anterior cruciate ligament (ACL)-deficient knee, a large posterior horn resection in this setting often increases tibial translation and instability symptoms.

Although many postmeniscectomy patients do very well and remain relatively asymptomatic for long periods, some patients develop pain earlier in the meniscal-deficient compartment as the result of increased articular contact stresses. It also must be remembered, however, that a degenerative meniscal tear may be the earliest symptomatic clinical event that signals a complicated degenerative pathway has been initiated, which is affected by more factors than just the status of the meniscus. Nonetheless, meniscal allograft transplantation has been developed to provide symptomatic relief to select patients and potentially slow the progression of degenerative changes. Since the first meniscus transplantation in 1984 by Milachowski was reported, the technique and its indications continue to be modified and improved. Contemporary meniscus allograft transplantation after menisectomy has been shown to decrease peak stresses and improve contact mechanics, but does not restore perfect knee mechanics (6, 7). Despite these potential benefits, this remains a difficult patient population to treat. Physicians must carefully evaluate potential meniscus transplant patients and help them maintain realistic outcome expectations.



Potential transplant patients are typically less than 50 years of age with an absent or nonfunctional meniscus who are symptomatic from their meniscal insufficiency. A detailed history regarding a patient’s specific symptoms, prior injuries, and subsequent surgery should be obtained. Recent arthroscopy pictures can be very helpful in determining the degree of meniscal resection and condition of the articular cartilage. Symptomatic postmenisectomy patients typically present with joint line tenderness, swelling, and activity-related pain. Symptoms may sometimes be subtle and can be associated with barometric pressure changes.

Patients with combined ACL instability and a deficient medial meniscus may complain soley of instability or combined instability and medial-sided pain. They may have a history of an ACL injury treated nonoperatively or may have recurrent instability following ACL reconstruction in the setting of a deficient medial meniscus.

Physical Examination

Physical examination should focus on location of the pain, alignment, gait, ligament stability, range of motion, muscle strength, and ruling out alternative pathology as the primary source of pain. Joint line tenderness is critical in determining the location and cause of the symptoms while ruling out other causes of pain. The pain or tenderness from meniscal deficiency is often dull and diffuse along the involved compartment. Sharp pain on McMurray test
may indicate recurrent meniscal injury or chondral lesion. Be sure to assess the knee for alternate causes of symptoms such as pes tendonitis. Evaluating a patient’s overall alignment and gait is important in determining if a corrective osteotomy needs to performed initially or potentially in combination with other procedures. Ligamentous stability should be assessed to determine the integrity and function of both the native ligaments and the prior reconstructions. Before considering a patient for meniscal transplant, the patient should have full symmetric range of motion and adequate muscle strength.

FIGURE 58.1. Illustration of proximal tibial soft tissue attachments.


Imaging starts with plain radiographs that include weight-bearing anteroposterior full extension views of both knees, weight-bearing posteroanterior views in 45° of flexion (Rosenberg view), Merchant view, and a nonweight-bearing flexion lateral view (Fig. 58.2). These films are helpful to assess the degree of degenerative changes and subtle joint space narrowing. If malalignment is suspected clinically, long-leg alignment films are indicated to provide an objective evaluation. MRI is often helpful to assess the integrety of the menisci, articular cartilage, and subchondral bone (Fig. 58.2). Bone scan may reveal increased activity in the involved compartment, but the sensitivity of bone scan in this setting unknown.

If the last arthroscopy occurred over 6 months to 1 year before evaluation, diagnostic arthroscopy is useful to evaluate the meniscus and articular cartilage before ordering meniscal allograft tissue (Fig. 58.2). Arthroscopy in this setting will accurately define extent of prior meniscectomy and the degree of arthrosis in cases where previous arthroscopic images are unavailable or unclear. When evaluating the knee for a possible meniscal transplant, the integrity of the articular cartilage is critical. Patients with less than Outerbridge grade 3 articular cartilage changes are optimal candidates for a meniscus transplant although small areas of grade 3 can sometimes
be accepted. In the setting of a focal grade 4 lesion, this focal area may be addressed with a concurrent cartilage resurfacing procedure.

FIGURE 58.2. Diagnostic imaging of knee before meniscal allograft transplant. A: Weight-bearing anteroposterior full extension views of both knees showing early medial compartment joint space narrowing following meniscal resection. B: MRI of knee showing medial meniscal deficiency. C: Arthroscopy image of meniscus-deficient medial compartment.

Differential Diagnosis

The differential diagnosis that should be considered includes recurrent meniscal tear, chondral or osteochondral lesion, advanced bipolar degenerative chondrosis, synovitis, pain emanating from the patellofemoral compartment, extra-articular knee sources (pes tendonitis/bursitis, neuroma), and hip or spine pathology. Any of these conditions may be the primary cause of symptoms rather than the proposed meniscal deficiency. However, in our experience, a small meniscal re-tear in the setting of a prior substantial meniscectomy rarely causes the patients primary symptoms. Although it may be difficult, a good examination combined with careful assessment of the studies can typically delineate who would be likely to benefit from a meniscus transplant. Injections can be helpful to differentiate intra-articular from extra-articular sources of pain. Certainly one of the most challenging aspects of meniscus transplant surgery is determining when moderate chondrosis has advanced to the point where a meniscal transplant is unlikely to yield a good clinical outcome. Although a chondral or osteochondral lesion may be the primary cause of pain in a meniscal-deficient compartment, meniscal deficiency may need to be addressed concurrently (i.e., chondroprotection of meniscus transplant).