You are in: eMedicine Specialties > Orthopedic Surgery > KNEE Discoid MeniscusArticle Last Updated: Oct 18, 2006AUTHOR AND EDITOR INFORMATIONSection 1 of 10
  Author: Ralph Di Libero, MD, Consulting Surgeon, Department of Orthopedic Surgery, Southern California Permanente Medical Group Ralph Di Libero is a member of the following medical societies: American Academy of Orthopaedic Surgeons, California Orthopedic Association, and Los Angeles County Medical Association Editors: Phillip J Marone, MD, Clinical Professor, Department of Orthopedic Surgery, Jefferson Medical College; Francisco Talavera, PharmD, PhD, Senior Pharmacy Editor, eMedicine; Thomas M DeBerardino, MD, Director, John A Feagin, Jr Sports Medicine Fellowship at West Point, Clinical Instructor in Surgery, Orthopedic Surgery Service, Keller Army Community Hospital at West Point; Dinesh Patel, MD, FACS, Associate Clinical Professor of Orthopedic Surgery, Harvard Medical School; Chief of Arthroscopic Surgery, Department of Orthopedic Surgery, Massachusetts General Hospital; Carlos J Lavernia, MD, FAAOS, Adjunct Clinical Professor, Department of Orthopedic Surgery, University of Miami School of Medicine; Medical Director, Orthopedic Institute at Mercy Hospital Author and Editor Disclosure Synonyms and related keywords: discoid lateral meniscus, discoid lateral menisci, hypermobile meniscus, hypermobile menisci, Wrisberg lateral meniscus, Wrisberg lateral menisci, knee pathology, misshapen lateral meniscus, misshapen lateral menisci, deformed lateral meniscus, deformed lateral menisci, kneecap deformity, knee cap deformity, deformed kneecap, deformed knee cap, kneecap pathology, knee cap pathology, knee arthroscopy, arthroscopic knee surgery INTRODUCTIONSection 2 of 10
  Discoid lateral menisci were first described in the late 1800s. The normal configuration of a meniscus is that of a matured crescent moon, whereas that of a discoid meniscus generally is a thickened, very early crescent moon. Variations of this general shape occur relatively rarely, and occasionally, the lunar appearance is also found in the medial meniscus. The discoid shape results in a membrane barrier that prevents normal contact between the articular surfaces of the knee and has a high incidence of mechanical deformation. ProblemOne element in the differential diagnosis of knee pathology is a discoid meniscus. Discoid meniscus can manifest itself as an abnormal band, medial and lateral in the same knee, bilateral and medial, or, more commonly, a discoid lateral meniscus (Lee, 2000; Choi, 2001; Akgun, 1998). FrequencyDiscoid lateral menisci have been reported to occur at the rate of 1.5-3% in the general population, whereas discoid medial menisci have been reported to occur at the rate of 0.1-0.3% (Ryu, 1998). The Asian population has a slightly higher rate of occurrence; Tokyo's Teishin Hospital reported 16.6% of all knees examined arthroscopically had a discoid lateral meniscus (Ikeuchi, 1982). EtiologyA discoid lateral meniscus results from a developmental anomaly before birth. After birth, no sudden change occurs in meniscal development (Clark, 1983). PathophysiologyTwo distinct types of discoid lateral meniscus exist. One is the hypermobile, or Wrisberg, lateral meniscus, and the other is a misshapen or discoid form of an otherwise normal lateral meniscus. Both types present unique pathophysiologic problems. The Wrisberg type lacks an attachment to stabilize the posterior horn to the tibia. It may also be of normal shape rather than discoid. The only attachment of the posterior horn is to the Wrisberg or meniscofemoral ligament. The general configuration produces an unstable or hypermobile lateral meniscus. ClinicalPatients present with any combination of pain, giving way, effusion, and clicking or snapping knee. Children with discoid meniscus usually present with a snapping knee joint, especially those around 7 years old. The snap can be seen and heard. Translation of the femoral condyle over a thickened posterior rim of lateral meniscus occurs. If the child remains otherwise asymptomatic, only observation is necessary; however, snapping greatly increases the chance of tearing the lateral meniscus, either by continued microtrauma or by trauma that would not cause tearing otherwise. INDICATIONSSection 3 of 10
Abnormalities of knee function, pain, and effusion are indications for surgical treatment. RELEVANT ANATOMYSection 4 of 10
Arthroscopic removal of a torn, normally configured lateral meniscus, in its entirety, is accomplished by first releasing the anterior horn, then releasing the attachment to the popliteal tendon, and then partially releasing the posterior horn. Finally, the meniscus is displaced into the intercondylar notch to complete the posterior release and remove the entire meniscus. A discoid lateral meniscus often has a continuous attachment from the popliteal tendon to the posterior horn. Removal of the anterior horn is necessary; the remainder of the discoid meniscus is then removed in a piecemeal fashion. An arthroscopic Bovie or other type of coagulation system should be available to stop possible bleeding from a branch of the lateral geniculate artery. CONTRAINDICATIONSSection 5 of 10
An otherwise asymptomatic knee with the incidental finding of discoid meniscus is a contraindication for surgical treatment. WORKUPSection 6 of 10
Imaging Studies
Diagnostic Procedures
TREATMENTSection 7 of 10
Surgical therapySurgical treatment varies according to the type of lateral discoid meniscus. Arthroscopic procedures are quite successful and are somewhat more technically demanding than are routine meniscal tear excisions because of the younger age, tighter joints, and less room available to manipulate arthroscopic equipment. Surgical techniques vary, from sculpting and partial meniscectomy to complete removal, starting with removal of the anterior portion for better arthroscopic visualization (Smith, 1999; Ogata, 1997). Because of the hypermobility of the entire meniscus in the Wrisberg (type III) deformity, sculpting the meniscus is ineffective, and better results have been reported with a near-complete to complete meniscectomy. Some attempts have been made to avoid total meniscectomy by tying down the meniscus through drill holes in the tibia to correct the anatomic defect. Using the Watanabe classification, the indicated treatment for tears of discoid meniscus type I (complete), type II (incomplete), and the central-holed or ring-shaped version is removal of the central discoid and ring portions, including any areas of tearing, followed by arthroscopic sculpting of the remaining meniscus (Monllau, 1998). Preoperative detailsThe preoperative and postoperative management of a torn discoid meniscus is the same as that for a torn lateral meniscus with a normal anatomy. COMPLICATIONSSection 8 of 10
Possible complications include the following:
MULTIMEDIASection 9 of 10
REFERENCESSection 10 of 10
Article Last Updated: Oct 18, 2006 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||
