Knee kinematics predicts that internal rotation of the femur on the tibia forces the medial meniscus posteriorly and toward the center of the joint. If a meniscal attachment is abnormally loaded (peripheral or otherwise), as the posterior portion of the meniscus is forced toward the center of the joint, it may be caught between the femur and tibia, and resultant meniscal tearing can occur with further extension of the joint.

Patients with meniscal injuries typically present with clinical symptoms of focal joint line pain, swelling, and discomfort at the extremes of motion as well as specific mechanical symptoms such as catching, locking, and loss of extension. Physical examination should include evaluation and assessment of anatomic and mechanical axial alignment as well as signs of effusion, antalgia, loss of motion, focal joint line point tenderness, joint locking/clicking, and pain with squatting in terminal flexion and with axial compression. Manual examination for meniscal pathology has been reported to have a sensitivity and specificity of 55% to 85% and 29% to 67%, respectively (6). Provocative maneuvers for meniscal pathology include McMurray’s test, the Apley grind or compression test, the Thessaly test, the Steinmann test, and Childress (squat) test (6, 7 and 8). McMurray’s test is performed by placing a varus or valgus stress to a flexed knee while extending, and is a reliable examination maneuver for diagnosing meniscal tears. The sensitivity of McMurray’s test has been reported at 16% to 37%, with specificity at 77% to 98%, and a positive predictive value of 83% (6, 7). Similarly, the Apley grind or compression test, performed by flexing the knee, rotating, and compressing, has been reported to have a sensitivity of 13% to 16%, a specificity of 80% to 90%, and overall accuracy of 28%. The Thessaly test, in which the patient stands flatfooted on the floor and rotates at the knee in 20° of flexion internally and externally, has been reported to have a sensitivity, specificity, and overall accuracy of 89%, 97%, and 94%, respectively for medial meniscus tears and 92%, 96%, 96%, respectively for lateral meniscus tears (8). The Steinmann test is performed as a flexed knee is internally and externally rotated at the foot, whereas the Childress (squat) test elicits symptoms with the patient fully squatting with feet in internal and external rotation. The Bounce home test is performed with the patient supine by holding the great toe or forefoot and then attempts to identify a sharp endpoint as a fully flexed knee is taken to full extension or even hyperextension. A positive test occurs when full extension is unable to be obtained.

Clinical assessment for meniscal tears should always include plain roentgengrams, which should be evaluated to assess for crystal arthropathy, osteoarthritis, osteonecrosis, osteochondral defects, and calcification. Radiographs
should include extension weight bearing anteroposterior, lateral, notch, and patella skyline views. Weight-bearing 45° flexion posteroanterior comparison views should also obtained to assess a narrowed joint space in cases where articular cartilage wear is suspected. Routine magnetic resonance imaging is often not necessary for diagnosis of meniscal injury but may prove valuable in a more comprehensive evaluation of the knee.

Decision making regarding meniscal repair is dependent upon tear characteristics (i.e., tear pattern, geometry, location, vascularity, size, stability, tissue viability, or quality), associated pathology, previous surgeries, and patient expectations and goals (10). Vertical longitudinal tears (77.5% of medial meniscal tears and 59.4% of lateral meniscal tears (9)) with minimal deformation in the vascularized peripheral meniscus are generally considered anatomically optimal for repair owing to their vascular potential for healing. Deformed or frayed oblique flaps, radial, horizontal cleavage, or degenerative complex tears within the avascular white-white zone have traditionally been treated with resection (10). Patient age, activity level, and postoperative rehabilitation compliance must also be taken into account before a decision is made regarding repair versus resection (Table 56.1).

Small, peripheral tears less than 7 mm in length and incomplete tears noted in the posterior horn of the lateral meniscus in a relatively asymptomatic patient (such as a patient undergoing concurrent anterior cruciate ligament reconstruction) can be left alone and be expected to heal. Shelbourne and Heinrich (11). concluded that posterior horn lateral meniscus tears, stable incomplete radial flap tears, or peripheral or posterior third tears within 1 cm of the popliteus tendon can be treated successfully and left in situ.
In contrast, surgical intervention is indicated in patients with unstable tissue, substantial peripheral longitudinal tears, mechanical symptoms, or when nonoperative measures (modification of activities, inflammation reduction, and physical therapy) fail.

Meniscal excision may alter load transmission, contact stresses, and tibiofemoral patholaxity (particularly in knees with associated anterior cruciate ligament [ACL] deficiency). Posterior root tears of the medial meniscus have been shown to increase peak contact pressure by 25% in the medial compartment and 13% in the lateral compartment than with an intact meniscus (12). Repair of the tear site returned peak contact pressures to baseline and showed significant improvement in medial compartment contact pressures, tibial external rotation, and lateral tibial translation. In addition, meniscectomy in athletes has been shown to lead to knee instability, radiographic changes, and reduction in functional activities as early as 4.5 years postsurgery (13). Clinical outcomes following partial meniscectomy reveal that radiographic progression of medial compartment osteoarthritis after medial meniscectomy was greater than lateral compartment osteoarthritis after lateral meniscectomy (14). Furthermore, when less than 50% of the meniscal rim remains, radiographic progression may be seen.

Fabricant et al. (15) reported on a level 1 prognostic prospective study of 126 arthroscopic partial meniscectomies evaluating first year postoperative recovery revealed that female gender and extent of chondral pathology affected knee pain, knee function, and overall physical knee status (effusion, flexion, extension, gait, and general progress) significantly. Age, body mass index, depth of meniscal excision (amount of meniscus removed from any zone), involvement of one or both menisci, and extent of meniscal tear (total number of zones involved) showed no association. Extent of the meniscal tear affected overall physical knee status but not knee pain or function. Meniscal excision and involvement of one or both menisci had no impact on recovery. McDermott and Amis (16) pointed out that negative factors affecting longterm prognosis include the amount of tissue resected, the location of resection (posterior horn worse than anterior
horn or bucket-handle tears), the disruption of retained circumferential fibers, lateral meniscectomy (worse than medial), a preexisting chondral lesion, varus alignment of the affected knee, ACL deficiency or ligamentous patholaxity, and increased postmeniscectomy activity levels. Further support is provided by a retrospective comparative study of medial versus lateral arthroscopic partial meniscectomies suggesting that a more optimal prognosis can be predicted with patients less than age 35, vertical tears, absence of cartilage damage, and an intact meniscal rim following meniscectomy (17). In addition to the consideration of the natural history of meniscal resection, patient counseling of the procedural risks, benefits, expected recovery and rehabilitation as well as the outcomes of selected treatment options are essential. Recovery time and re-tear risks should also be addressed and may play a role in decision making when an expeditious and more predictable return to work or sport is preferred.

Meniscus repair techniques include open, arthroscopically assisted, and all-arthroscopic methods. Currently, arthroscopic-assisted meniscal repair techniques are considered preferable owing to shorter operative times and reduced patient morbidity.

The outside-in technique initially described by Rodeo and (22), is best indicated in meniscal tears involving the mid- and anterior one-third portions of the meniscus and for provisional fixation and stabilization of unstable tear fragments (use of traction and reducing stitch). An 18G spinal needle is passed percutaneously from outside to inside the joint through the meniscal tear. The technique allows for placement of variable suture patterns for repair while maintaining a safe vector, well anterior to the posterior neurovascular bundle.