Meniscal Lesions: Diagnosis and Treatment

Robert S. P. Fan, MD, Richard K. N. Ryu, MD

Disclosures
In This Article

Discoid Meniscus

The discoid meniscus is an anatomic variant that primarily affects the lateral meniscus. Rarely, it has also been shown to affect the medial side.

Watanabe[45] has classified the discoid meniscus as complete, incomplete, and Wrisberg ligament types. Complete and incomplete discoid menisci vary in their degree of tibial plateau coverage. The Wrisberg ligament type is fairly normal in shape, but there is no posterior coronary ligament attachment. Instead, the lateral meniscus attaches to the meniscofemoral ligament of Wrisberg (Figure 14).

Watanabe classification of discoid lateral meniscus: (A) Incomplete, (B) Complete, (C) Wrisberg-ligament variant. (Reprinted with permission.)

Neuschwander DC, Dres D, Finney TP. Lateral meniscal variant with absence of the posterior coronary ligament. J Bone Joint Surg Am. 1992;74: 1186-1190.

The discoid meniscus is an uncommon finding. The incidence has varied from 0.4% to 5% in arthroscopic studies. Interestingly, the incidence from studies in the Japanese and Korean populations has ranged from 8% to 15%.[46]

The discoid lateral meniscus was first described in 1887.[47] Smillie[48] wrote that the discoid meniscus represented a relative failure of absorption during different stages of development. Alternatively, Kaplan,[49] in 1957, described how abnormal motion of the discoid meniscus might lead to hypertrophy and result in a discoid shape. The exact etiology of discoid meniscus remains unclear.

The discoid lateral meniscus is usually asymptomatic (Figure 15). With the complete and incomplete types, the menisci usually become symptomatic when a meniscal tear occurs. Consequently, the signs and symptoms of the pathology are more reflective of a meniscal tear. The discoid meniscus is then identified upon arthroscopy.

Discoid meniscus.

The snapping knee syndrome is usually associated with the Wrisberg ligament variant. Abnormal motion of the meniscus results from the lack of posterior capsular attachment. Subluxation of the meniscus through flexion and extension then results in a snapping sensation at the joint line.

The treatment of a discoid meniscus depends on its type and association with a tear. If a discoid meniscus is discovered without evidence of a tear, then its presence should be considered incidental, and it should be left intact. If a tear is associated with a complete or incomplete discoid meniscus, then partial meniscectomy should be performed as a saucerization technique. The goal should be to resect enough tissue to result in a well-contoured, 6-mm stable rim.[50,51] For the Wrisberg ligament variant, the traditional treatment has been total meniscectomy. More recently, techniques have been developed to reduce the meniscus and repair it by providing a posterior attachment.[52]

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