- Author: Bradley S Baker, MD; Chief Editor: Craig C Young, MD more...
Meniscal injuries may be the most common knee injury. Meniscus tears (see the image below) are sometimes related to trauma, but significant trauma is not necessary. A sudden twist or repeated squatting can tear the meniscus.
Signs and symptoms
Most meniscal injuries can be diagnosed by obtaining a detailed history. Important points to address include the following:
Mechanism of injury (eg, twisting, squatting, changes in position)
Pain (commonly intermittent and usually localized to the joint line)
Mechanical complaints (eg, clicking, catching, locking, pinching, or a sensation of giving way)
Swelling (usually delayed, sometimes absent; degenerative tears often manifest with recurrent effusions)
Physical findings that are significant in the examination of a patient with a possible meniscus injury include the following:
Joint line tenderness (77-86% of patients with a meniscal tear)
Effusion (~50% of patients presenting with a meniscal tear)
Impaired range of motion – A mechanical block to motion or frank locking can occur with displaced tears; restricted motion commonly results from pain or swelling
Provocative maneuvers that may elicit characteristic results in the presence of a meniscal tear include the following:
McMurray test – Pain or a reproducible click
Steinmann test – Asymmetric pain with external (medial meniscus) or internal (lateral meniscus) rotation
Apley test – Pain at the medial or lateral joint
Thessaly test – Pain or a locking or catching sensation at the medial or lateral joint line
Similar tests, including those that elicit the Bragard, Böhler, Payr, Merke, Childress, and Finochietto signs
See Presentation for more detail.
Imaging studies that may be considered include the following:
Plain radiography – Anteroposterior weight-bearing view, posteroanterior 45° flexed view, lateral view, and Merchant patellar view
Arthrography – Once the standard imaging study for meniscal tears but now largely supplanted by magnetic resonance imaging (MRI)
MRI – Criterion standard for imaging meniscus pathology and all intra-articular disorders
Abnormal meniscal signals on MRI are classified into the following groups:
Grade I – Small area of increased signal within the meniscus
Grade II – Linear area of increased signal that does not extend to an articulating surface
Grade III – Abnormal increased signal that reaches the surface or edge of the meniscus (indicative of meniscal tearing)
Root tears – Meniscal extrusion of at least 3 mm in the mid-coronal plane 
In competent hands, arthroscopy is the best tool for meniscal tear diagnosis, with sensitivity, specificity, and accuracy approaching 100%. Being both therapeutic and diagnostic, it offers the option of immediate treatment of most disorders.
See Workup for more detail.
Conservative treatment should be attempted in all but the most severe cases. In the acute phase, such treatment may include the following:
Home physical therapy program
Simple rest with activity modification
Nonsteroidal anti-inflammatory drugs (NSAIDs)
If conservative treatment does not lead to resolution, surgical treatment is considered. Surgical options (arthroscopic or open) include the following:
Partial meniscectomy – The treatment of choice for tears in the avascular portion of the meniscus or complex tears that are not amenable to repair
Meniscus repair – Recommended for tears that occur in the vascular region (red zone or red-white zone), are longer than 1 cm, root tears, involve greater than 50% of the meniscal thickness, and are unstable to arthroscopic probing
In cases of previous total or subtotal meniscectomy, meniscus transplantation – A relatively new procedure for which specific indications and long-term results have not yet been clearly established
In the recovery phase, physical therapy may involve the following:
Partial meniscectomy – Low-impact or nonimpact workouts on postoperative day 1, advancing rapidly to preoperative activities; this can usually be accomplished without formal physical therapy, but such therapy should be initiated if deficits persist
Meniscus repair – More intensive rehabilitation; one option is avoidance of weight bearing for 4-6 weeks, with full motion encouraged; the authors prefer to allow full weight bearing with the knee braced and locked in full extension for 6 weeks, while encouraging full motion when the knee is not bearing weight
Medical therapy can be used during trials of nonoperative management with associated rest, ice, and a rehabilitation program. If surgical treatment is indicated, medical therapy is valuable in postoperative management.
See Treatment and Medication for more detail.
Our understanding of the meniscus has changed radically in the last century. In 1887, Sutton described the meniscus as "the functionless remains of a leg muscle." Not until 1948 did Fairbanks appreciate that "meniscectomy is not wholly innocuous," in his classic report of postmeniscectomy radiographic changes. Research and knowledge of the meniscus has continued. The critical importance of the meniscus of the knee joint is now understood.
Note the contrasting images below.
For patient education resources, see the Foot, Ankle, Knee, and Hip Center and Arthritis Center, as well as Knee Pain and Knee Injury.
See the list below:
Meniscal injuries may be the most common knee injury. The prevalence of acute meniscal tears is 61 cases per 100,000 persons.
The overall male-to-female incidence is approximately 2.5:1. The peak incidence of meniscal injury for males is in those aged 31-40 years. For females, the peak incidence is in those aged 11-20 years.
In patients older than 65 years, the rate of degenerative meniscal tears is 60%.
Root tears are observed in 28% of medial meniscal tears. 
Surgical procedures of the meniscus are performed on an estimated 850,000 patients each year. 
Estimates indicate that at least twice the number of meniscus procedures in the United States are performed worldwide.
The menisci are 2 semilunar wedges in the knee joint positioned between the tibia and the femur. They are essentially extensions of the tibia that act to deepen the articular surfaces of the otherwise relatively flat tibial plateau to accommodate the relatively round femoral condyles. The superior surfaces are concave and in contact with the femoral condyles; the inferior surfaces are flat and conform to the tibial plateaus. The peripheral, convex borders of the menisci are thick and attach to the joint capsule; the opposite border tapers inward to a thin, free edge centrally. Therefore, menisci have a triangular shape in cross section. Each covers approximately two thirds of the corresponding articular surface of the tibia. The medial and lateral menisci each have distinct, individual anatomic characteristics.[6, 7, 8]
The medial meniscus is semicircular or C-shaped and approximately 3.5 cm in length from anterior to posterior. It is asymmetric with a considerably wider posterior horn than anterior horn. Peripherally, the medial meniscus is continuously attached to the joint capsule, with the middle portion being more firmly attached via connection with fibers of the deep medial collateral ligament. It is anchored to the tibia by the coronary (meniscotibial) ligaments.
The posterior horn of the medial meniscus inserts in the posterior intercondylar fossa directly anterior to the posterior cruciate ligament. The anterior horn attachment is more variable, distributed in a 6- to 8-mm area anterior to the anterior cruciate ligament (ACL) tibial attachment in the anterior intercondylar fossa. Some anterior fibers attach over the anterior periphery of the tibial articular surface, and some posterior fibers of the anterior horn merge with the transverse meniscal ligament that connects to the lateral meniscus.
The lateral meniscus is more nearly circular or O-shaped and covers a larger portion of the tibial plateau surface than the medial meniscus. Its length from anterior to posterior is slightly less than the medial meniscus, and it has an almost uniform width. There is attachment to the joint capsule peripherally, except in the region of the middle one third, where there is no attachment but rather a hiatus for the popliteal tendon.
Unlike the medial meniscus, there is no attachment of the lateral meniscus to the lateral collateral ligament, but the lateral meniscus is anchored to the tibia via coronary (meniscotibial) ligaments. Posteriorly, the lateral meniscus is uniquely attached to the medial femoral condyle by meniscofemoral ligaments. These ligaments are highly variable and pass anterior (ligament of Humphrey) and/or posterior (ligament of Wrisberg) to the posterior cruciate ligament. The posterior attachment to the tibia is just anterior to the medial meniscus attachment in the posterior intercondylar fossa. The anterior horn inserts anterior to the lateral tibial spine and in close proximity to the ACL tibial insertion. Some fibers actually may blend into the ACL.
Despite their attachments, both menisci have mobility. The medial meniscus, with excursion of approximately 5 mm, is half as mobile as the lateral meniscus, whose mobility may exceed 10 mm. The anterior horns are more mobile than the posterior horns. This mobility allows for improved conformity of the tibiofemoral joint. Because the posterior horn of the medial meniscus has the least movement, it is at greatest risk for disruption.
The microanatomy of the meniscus is dense fibrocartilage composed of cells and an extracellular matrix of collagen fibers in network. The cells are termed fibrochondrocytes because they appear to be a mixture of fibroblasts and chondrocytes. These cells are responsible for the synthesis and maintenance of the extracellular fibrocartilaginous matrix.
The most abundant component of the menisci is collagen (75%)—mainly type I collagen (>90%) but it also contains types II, III, V, and VI. Collagen fibers are arranged mostly along a longitudinal or circumferential direction, with some interwoven radial and oblique fibers. The circumferential fibers are related directly to the menisci's functional ability to dissipate compressive loads. The other fibers act primarily as ties to enhance structural rigidity and to help prevent longitudinal splitting. The extracellular matrix also includes proteoglycans, glycoproteins, and elastin.
Most meniscal tissue is avascular and depends on passive diffusion and mechanical pumping to provide nutrition to the fibrocytes within the meniscal substance. Arnoczky and Warren demonstrated the important vascular anatomy of the menisci.[9, 10] The limited peripheral blood supply originates from the medial and lateral inferior and superior geniculate arteries. Branches from these vessels give rise to a perimeniscal capillary plexus within the synovium and joint capsule, which, in turn, supplies the meniscus periphery.
Studies have shown that 10-30% of the periphery of the medial meniscus and 10-25% of the lateral meniscus receives a vascular supply; the remainder receives its nutrition from the synovial fluid from passive diffusion and mechanical pumping. A few terminal branches of these vessels, along with the middle geniculate artery through the synovial covering of the anterior and posterior horn attachments, supply increased vascularity to the meniscal horns. The potential for vascular ingrowth is essential for successful meniscal healing and surgical repair. Various zones of the meniscus are described based on the blood supply; the red zone is the well-vascularized periphery, the red-white zone is the middle portion with vascularity peripherally but not centrally, and the white zone is the central avascular portion.
The neuroanatomy of the meniscus is not well described. However, the distribution of neural elements has been demonstrated in essentially the same anatomic distribution as the vascular supply. The anterior and posterior horns are the most richly innervated, and the body innervation follows the pattern along the periphery. Although not entirely clear, these nerve endings are believed to play a role in sensory feedback and proprioception. The greater innervation of the horns of the meniscus reflects the need for feedback at the extremes of flexion and extension, when the meniscal horns are compressed and neural elements are activated.[6, 7, 8]
The meniscus has unique anatomic properties. An understanding of this anatomy is essential to comprehending its important functions, which include load bearing, load and force distribution, joint stability, joint lubrication, and proprioception.[6, 7, 11] One of the primary functions is to provide load bearing across the knee joint. Fifty percent of the compressive load in the knee is transferred by the menisci in extension, whereas up to 85% of the load is transferred at 90° of flexion. The collagen orientation makes this load bearing possible by converting the compressive forces to tensile forces.
Load and forces are distributed across a much larger surface area because of the menisci, which (1) decrease focal contact pressure by increasing the contact area and (2) protect the underlying articular cartilage. Resection of 15-34% of a meniscus may increase contact pressure by more than 350%. Normal knees have 20% better shock-absorbing capacity than meniscectomized knees.
Joint stability is increased because of meniscal structure, which allows increased congruence and conformity between the femoral condyles and tibial plateaus.[6, 7] The wedge-shaped meniscus attached to the tibia serves as a secondary stabilizer. For example, the posterior horn acts as a shim to resist anterior tibial translation relative to the femur. Meniscectomy alone may not increase knee laxity, but it has been shown that in association with ACL deficiency, anterior laxity is increased. Meniscal lubrication occurs by fluid exudation across the surface, much like articular cartilage.
The classification of meniscal tears provides a description of pathoanatomy. The types of meniscus tears include the following:
Longitudinal tears that may take the shape of a bucket handle if displaced
Parrot-beak or oblique flap tears
Complex tears that combine variants of the above
Costa CR, Morrison WB, Carrino JA. Medial meniscus extrusion on knee MRI: is extent associated with severity of degeneration or type of tear?. AJR Am J Roentgenol. 2004 Jul. 183(1):17-23. [Medline].
Bland-Sutton J. Ligaments: Their Nature and Morphology. 2nd ed. London, UK: HK Lewis; 1887.
Fairbanks TJ. Knee joint changes after meniscectomy. J Bone Joint Surg Br. 1948. 30:664-70. [Full Text].
Bin SI, Kim JM, Shin SJ. Radial tears of the posterior horn of the medial meniscus. Arthroscopy. 2004 Apr. 20(4):373-8. [Medline].
Arendt EA, ed. Orthopaedic Knowledge Update: Sports Medicine 2. Rosemont, Ill: American Academy of Orthopaedic Surgeons; 1999.
Insall JN, Scott WN, eds. Surgery of the Knee. 3rd ed. Philadelphia, Pa: WB Saunders Co; 2001.
Rodkey WG. Basic biology of the meniscus and response to injury. Instr Course Lect. 2000. 49:189-93. [Medline].
Fu FH, Harner CD, Vince KG, eds. Knee Surgery. Philadelphia, Pa: Lippincott Williams & Wilkins; 1994.
Arnoczky SP, Warren RF. The microvasculature of the meniscus and its response to injury. An experimental study in the dog. Am J Sports Med. 1983 May-Jun. 11(3):131-41. [Medline].
Arnoczky SP, Warren RF. Microvasculature of the human meniscus. Am J Sports Med. 1982 Mar-Apr. 10(2):90-5. [Medline].
Vaziri A, Nayeb-Hashemi H, Singh A, Tafti BA. Influence of meniscectomy and meniscus replacement on the stress distribution in human knee joint. Ann Biomed Eng. 2008 May 22. epub ahead of print. [Medline].
Lee JH, Lim YJ, Kim KB, Kim KH, Song JH. Arthroscopic pullout suture repair of posterior root tear of the medial meniscus: radiographic and clinical results with a 2-year follow-up. Arthroscopy. 2009 Sep. 25(9):951-8. [Medline].
Eren OT. The accuracy of joint line tenderness by physical examination in the diagnosis of meniscal tears. Arthroscopy. 2003 Oct. 19(8):850-4. [Medline].
Behairy NH, Dorgham MA, Khaled SA. Accuracy of routine magnetic resonance imaging in meniscal and ligamentous injuries of the knee: comparison with arthroscopy. Int Orthop. 2008 May 28. epub ahead of print. [Medline].
Nikolaou VS, Chronopoulos E, Savvidou C, et al. MRI efficacy in diagnosing internal lesions of the knee: a retrospective analysis. J Trauma Manag Outcomes. 2008 Jun 2. 2(1):4. [Medline].
Lerer DB, Umans HR, Hu MX, Jones MH. The role of meniscal root pathology and radial meniscal tear in medial meniscal extrusion. Skeletal Radiol. 2004 Oct. 33(10):569-74. [Medline].
Spindler KP, McCarty EC, Warren TA, Devin C, Connor JT. Prospective comparison of arthroscopic medial meniscal repair technique: inside-out suture versus entirely arthroscopic arrows. Am J Sports Med. 2003 Nov-Dec. 31(6):929-34. [Medline].
Bin SI, Kim JM, Shin SJ. Radial tears of the posterior horn of the medial meniscus. Arthroscopy. 2004 Apr. 20(4):373-8. [Medline].
Shelbourne KD, Heinrich J. The long-term evaluation of lateral meniscus tears left in situ at the time of anterior cruciate ligament reconstruction. Arthroscopy. 2004 Apr. 20(4):346-51. [Medline].
Nicholas SJ, Golant A, Schachter AK, Lee SJ. A new surgical technique for arthroscopic repair of the meniscus root tear. Knee Surg Sports Traumatol Arthrosc. 2009 Dec. 17(12):1433-6. [Medline].
Logan M, Watts M, Owen J, Myers P. Meniscal repair in the elite athlete: results of 45 repairs with a minimum 5-year follow-up. Am J Sports Med. 2009 Jun. 37(6):1131-4. [Medline].
Kim SB, Ha JK, Lee SW, Kim DW, Shim JC, Kim JG, et al. Medial meniscus root tear refixation: comparison of clinical, radiologic, and arthroscopic findings with medial meniscectomy. Arthroscopy. 2011 Mar. 27(3):346-54. [Medline].
Adachi N, Ochi M, Uchio Y, Kuriwaka M, Shinomiya R. Torn discoid lateral meniscus treated using partial central meniscectomy and suture of the peripheral tear. Arthroscopy. 2004 May. 20(5):536-42. [Medline].
Kelly JD 4th, Ebrahimpour P. Chondral injury and synovitis after arthroscopic meniscal repair using an outside-in mulberry knot suture technique. Arthroscopy. 2004 May. 20(5):e49-52. [Medline].
Barber FA, Harding NR. Meniscal repair rehabilitation. Instr Course Lect. 2000. 49:207-10. [Medline].
Lozano J, Ma CB, Cannon WD. All-inside meniscus repair: a systematic review. Clin Orthop Relat Res. 2007 Feb. 455:134-41. [Medline].
Grant JA, Wilde J, Miller BS, Bedi A. Comparison of inside-out and all-inside techniques for the repair of isolated meniscal tears: a systematic review. Am J Sports Med. 2012 Feb. 40(2):459-68. [Medline].
Nepple JJ, Dunn WR, Wright RW. Meniscal repair outcomes at greater than five years: a systematic literature review and meta-analysis. J Bone Joint Surg Am. 2012 Dec 19. 94(24):2222-7. [Medline]. [Full Text].
Allaire R, Muriuki M, Gilbertson L, Harner CD. Biomechanical consequences of a tear of the posterior root of the medial meniscus. Similar to total meniscectomy. J Bone Joint Surg Am. 2008 Sep. 90(9):1922-31. [Medline].
LaPrade CM, Jansson KS, Dornan G, Smith SD, Wijdicks CA, LaPrade RF. Altered tibiofemoral contact mechanics due to lateral meniscus posterior horn root avulsions and radial tears can be restored with in situ pull-out suture repairs. J Bone Joint Surg Am. 2014 Mar 19. 96(6):471-9. [Medline].
Marzo JM, Kumar BA. Primary repair of medial meniscal avulsions: 2 case studies. Am J Sports Med. 2007 Aug. 35(8):1380-3. [Medline].
Kim YM, Rhee KJ, Lee JK, Hwang DS, Yang JY, Kim SJ. Arthroscopic pullout repair of a complete radial tear of the tibial attachment site of the medial meniscus posterior horn. Arthroscopy. 2006 Jul. 22(7):795.e1-4. [Medline].
West RV, Kim JG, Armfield D, Harner CD. Lateral meniscal root tears associated with anterior cruciate ligament injury: classification and management (SS-70). Arthroscopy. 2004. 20:e32-e33.
Ahn JH, Wang JH, Lim HC, et al. Double transosseous pull out suture technique for transection of posterior horn of medial meniscus. Arch Orthop Trauma Surg. 2009 Mar. 129(3):387-92. [Medline].
Kim JH, Shin DE, Dan JM, Nam KS, Ahn TK, Lee DH. Arthroscopic suture anchor repair of posterior root attachment injury in medial meniscus: technical note. Arch Orthop Trauma Surg. 2009 Aug. 129(8):1085-8. [Medline].
Kim SB, Ha JK, Lee SW, et al. Medial meniscus root tear refixation: comparison of clinical, radiologic, and arthroscopic findings with medial meniscectomy. Arthroscopy. 2011 Mar. 27(3):346-54. [Medline].
Kim JH, Chung JH, Lee DH, Lee YS, Kim JR, Ryu KJ. Arthroscopic suture anchor repair versus pullout suture repair in posterior root tear of the medial meniscus: a prospective comparison study. Arthroscopy. 2011 Dec. 27(12):1644-53. [Medline].
Ahn JH, Lee YS, Yoo JC, Chang MJ, Park SJ, Pae YR. Results of arthroscopic all-inside repair for lateral meniscus root tear in patients undergoing concomitant anterior cruciate ligament reconstruction. Arthroscopy. 2010 Jan. 26(1):67-75. [Medline].
Khan M, Evaniew N, Bedi A, Ayeni OR, Bhandari M. Arthroscopic surgery for degenerative tears of the meniscus: a systematic review and meta-analysis. CMAJ. 2014 Oct 7. 186 (14):1057-64. [Medline].
Kise NJ, Risberg MA, Stensrud S, Ranstam J, Engebretsen L, Roos EM. Exercise therapy versus arthroscopic partial meniscectomy for degenerative meniscal tear in middle aged patients: randomised controlled trial with two year follow-up. BMJ. 2016 Jul 20. 354:i3740. [Medline].
Frellick M. Exercise as Effective as Surgery for Meniscal Tears. Medscape Medical News. Available at http://www.medscape.com/viewarticle/866424. July 21, 2016; Accessed: July 25, 2016.
Hart ES, Kalra KP, Grottkau BE, Albright M, Shannon EG. Discoid lateral meniscus in children. Orthop Nurs. 2008 May/June. 27(3):174-9. [Medline].
Choi NH, Kim TH, Victoroff BN. Comparison of arthroscopic medial meniscal suture repair techniques: inside-out versus all-inside repair. Am J Sports Med. 2009 Nov. 37(11):2144-50. [Medline].
Cox CL, Deangelis JP, Magnussen RA, Fitch RW, Spindler KP. Meniscal tears in athletes. J Surg Orthop Adv. 2009 Spring. 18(1):2-8. [Medline].
Ding J, Zhao J, He Y, Huangfu X, Zeng B. Risk factors for articular cartilage lesions in symptomatic discoid lateral meniscus. Arthroscopy. 2009 Dec. 25(12):1423-6. [Medline].
Freedman KB, Nho SJ, Cole BJ. Marrow stimulating technique to augment meniscus repair. Arthroscopy. 2003 Sep. 19(7):794-8. [Medline].
Iwamoto J, Takeda T, Sato Y, Matsumoto H. Retrospective case evaluation of gender differences in sports injuries in a Japanese sports medicine clinic. Gend Med. 2008 Dec. 5(4):405-14. [Medline].
Jerosch J, Riemer S. [How good are clinical investigative procedures for diagnosing meniscus lesions?] [German]. Sportverletz Sportschaden. 2004 Jun. 18(2):59-67. [Medline].
Kisiday JD, Vanderploeg EJ, McIlwraith CW, Grodzinsky AJ, Frisbie DD. Mechanical injury of explants from the articulating surface of the inner meniscus. Arch Biochem Biophys. 2009 Nov 24. epub ahead of print. [Medline].
Lowry F. Real knee surgery no better than sham for meniscal tear. Medscape Medical News. December 27, 2013. Available at http://www.medscape.com/viewarticle/818399. Accessed: January 7, 2014.
Metcalf MH, Barrett GR. Prospective evaluation of 1485 meniscal tear patterns in patients with stable knees. Am J Sports Med. 2004 Apr-May. 32(3):675-80. [Medline].
Oei EH, Koster IM, Hensen JH, et al. MRI follow-up of conservatively treated meniscal knee lesions in general practice. Eur Radiol. 2009 Nov 17. epub ahead of print. [Medline]. [Full Text].
Pearse EO, Craig DM. Partial meniscectomy in the presence of severe osteoarthritis does not hasten the symptomatic progression of osteoarthritis. Arthroscopy. 2003 Nov. 19(9):963-8. [Medline].
Sihvonen R, Paavola M, Malmivaara A, Itälä A, Joukainen A, Nurmi H, et al. Arthroscopic partial meniscectomy versus sham surgery for a degenerative meniscal tear. N Engl J Med. 2013 Dec 26. 369(26):2515-24. [Medline].
Uysal M, Akpinar S, Bolat F, et al. Apoptosis in the traumatic and degenerative tears of human meniscus. Knee Surg Sports Traumatol Arthrosc. 2008 Apr 30. epub ahead of print. [Medline].