summary Meniscal tears are common sports-related injuries in young athletes and can also present as a degenerative condition in older patients. Diagnosis can be suspected clinically with joint line tenderness and a positive McMurray's test, and can be confirmed with MRI studies. Treatment can be nonoperative versus operative (partial meniscectomy versus repair) depending on the morphology of the meniscus tear, root involvement, patient symptoms, and patient activity demands. Epidemiology Incidence very common most common indication for knee surgery Risk factor higher risk in ACL deficient knees Etiology Pathophysiology medial tears more common than lateral tears the exception is in the setting of an acute ACL tear where lateral tears are more common degenerative tears in older patients usually occur in the posterior horn medial meniscus lateral tears more common in acute ACL tears Anatomy Anatomy of meniscus Classification Descriptive classification location red zone (outer third, vascularized) red-white zone (middle third) white zone (inner third, avascular) position (anterior, middle, posterior third, root) size pattern vertical/longitudinal common, especially with ACL tears repair when peripheral bucket handle vertical tear which may displace into the notch oblique/flap/parrot beak may cause mechanical locking symptoms radial complete radial tears that extend to the meniscocapsular junction are biomechanically equivalent to posterior root tears horizontal more common in older population may be associated with meniscal cysts complex root functionally equivalent to a total meniscectomy lateral root tears associated with ACL tears medial root tears associated with chondral injuries Presentation Symptoms pain localizing to medial or lateral side mechanical symptoms (locking and clicking), especially with squatting delayed or intermittent swelling Physical exam joint line tenderness is the most sensitive physical examination finding effusion provocative tests Apley compression prone-flexion compression Thessaly test standing at 20 degrees of knee flexion on the affected limb, the patient twists with knee external and internal rotation with positive test being discomfort or clicking. McMurray's test flex the knee and place a hand on medial side of knee, externally rotate the leg and bring the knee into extension. a palpable pop / click + pain is a positive test and can correlate with a medial meniscus tear. Imaging Radiographs Should be normal in young patients with an acute meniscal injury Meniscal calcifications may be seen in crystalline arthropathy (ex. CPPD) MRI indications MRI is most sensitive diagnostic test, but also has a high false positive rate findings MRI grade III signal is indicative of a tear linear high signal that extends to either superior or inferior surface of the meniscus parameniscal cyst indicates the presence of a meniscal tear bucket handle meniscal tears indicated by "double PCL" sign "double anterior horn" sign meniscal extrusion or "ghost sign," may indicate meniscal root tear MCL sprain pain with valgus stress at 30° knee flexion, which isolates the superficial MCL gapping of medial joint line Plica syndrome pain is typically in the medial parapatellar region may have palpable medial parapatellar cord Osteochondral lesions may present very similarly differentiated with imaging (MRI) Treatment Nonoperative rest, NSAIDS, rehabilitation indications indicated as first line treatment for degenerative tears outcomes improvement in knee function following physical therapy "noninferior" when compared to arthroscopic partial meniscectomy Operative partial meniscectomy indications tears not amenable to repair (complex, degenerative, radial tear patterns) repair failure >2 times outcomes >80% satisfactory function at minimum follow-up 50% have Fairbanks radiographic changes (osteophytes, flattening, joint space narrowing) predictors of success age <40yo normal alignment minimal or no arthritis single tear meniscal repair indications best candidate for repair is a tear with the following characteristics peripheral in the red-red zone (vascularized region) lower rim width correlates with the ability of a meniscal repair to heal rim width is the distance from the tear to the peripheral meniscocapsular junction (better blood supply). vertical and longitudinal tear rather than radial, horizontal or degenerative tear bucket handle meniscus tear 1-4 cm in length root tear acute repair combined with ACL reconstruction traditional literature report higher healing rates with concurrent ACL reconstruction current literature shows no difference in healing for 2nd generation all-inside repairs with/without concomitant ACL reconstruction outcomes 70-95% successful highest success when done with concomitant ACL reconstruction (90%) modest result when done with an intact ACL (60%) poor results with untreated ACL-deficiency (30%) meniscal transplantation indications controversial young patients with near-total meniscectomy, especially lateral contraindications inflammatory arthritis instability marked obesity grade III and IV chondral changes malalignment (if not concurrently addressed) diffuse arthritis outcomes requires 8-12 months for graft to fully heal return to sports by 6-9 months 10 year follow-up showed: persistent improvement in subjective pain and function scores most had radiographic progression of degenerative changes re-tears or extrusion are common total meniscectomy of historical interest only outcomes 20% have significant arthritic lesions and 70% have radiographic changes three years after surgery 100% have arthrosis at 20 years severity of degenerative changes is proportional to % of the meniscus that was removed Techniques Rest, NSAIDS, rehabilitation technique PWB, ROM as tolerated Partial Meniscectomy approach standard arthroscopic approach technique minimize resection (DJD proportional to amount removed) do not use thermal (heat probes) postoperative early active range of motion prolonged immobilization (10 weeks) is detrimental to healing in a dog model Meniscal repair approach inside-out technique considered gold standard medial approach to capsule expose capsule by incising the sartorius fascia retract pes tendons / semimembranosus posteriorly developing plane between the medial gastrocnemius and capsule lateral approach to capsule develop plane between IT band and biceps tendon then retract lateral head of gastrocnemius posteriorly all-inside technique (suture devices with plastic or bioabsorbable anchors) most common allows tensioning of the construct many complications (device breakage, iatrogenic chondral injury) outside-in repair useful for anterior horn tears open repair uncommon except in trauma, knee dislocations technique vertical mattress sutures are strongest because they capture circumferential fibers healing is enhanced by rasping knee flexion beyond 90 degrees should be avoided postoperatively risks saphenous nerve and vein (medial approach) peroneal nerve (lateral approach) popliteal vessels Meniscal Transplantation technique bone to bone healing with plugs at each horn or a bridge between horns peripheral vertical mattress sutures correct sizing of the allograft is essential (commonly based on radiographs, within 5-10% error tolerated) oversizing leads to meniscal extrusion undersizing results in poor congruity and increased load transmission Complications Saphenous neuropathy (7%) Arthrofibrosis (6%) Sterile effusion (2%) Peroneal neuropathy (1%) Superficial infection (1%) Deep infection (1%)