Symptoms may include lateral-sided knee pain or mechanical symptoms (clicking, clunking, snapping, popping, locking) which adversely affect a child’s gait (ie, limping), activities of daily life, sports, or participation in recreational activities (eg, free play, playground activities, gym class)

Even in the setting of minimal or no symptoms, the presence of a true tear within a discoid meniscus should warrant consideration of proactive surgical treatment, so as to remove the tear, “stabilize” the free edges of the meniscus, and prevent the tear from propagating or worsening. Progression of a small tear to a large, complex, or degenerative tear may preclude meniscal preservation and lead to the need for subtotal or total meniscectomy, after which an accelerated rate of arthritis may be predicted at a young age¹,²,³,⁴

Radiologic assessment of a tear within a discoid meniscus can be more complex than that in a normal meniscus. Therefore, a higher resolution, higher quality (eg, 3 T magnet) magnetic resonance imaging (MRI) study may be helpful

One or more different tear patterns may be seen, including radial, vertical, horizontal, or complex/degenerative tears, as well as meniscocapsular separation or instability. Intermediate or high signal abnormality in the middle of a complete or near-complete discoid meniscus is not necessarily a horizontal cleavage tear, particularly if there is no extension of the signal abnormality to the central free edge or to the superior or inferior meniscal surface

If intrasubstance signal abnormality is detected in the absence of significant symptoms, and the shared decision-making process with a patient’s family results in a decision for nonoperative treatment, close observation or monitoring should be pursued, in the form of annual clinical checks and consideration of serial MRI studies

If there is worsening of the radiologic appearance, or if symptoms worsen, surgical treatment may allow for a more successful overall meniscal preservation strategy, though this has not been clearly established in the literature

While more prospective research is needed on the controversial topic of timing of discoid meniscus surgery, the author believes that a “wait and see” approach—in which surgery is deferred until symptoms become severe or functionally limiting or more definitive tear patterns are identified—may represent a suboptimal strategy, from a long-term joint preservation perspective

A lateral knee post is used on a standard operating room (OR) table to ensure adequate valgus stress for visualization of the medial compartment during the diagnostic arthroscopy portion of the procedure

Most of the surgery is performed with the knee in the figure-4 position (see Figure 35.2), in which the knee is flexed to 60° to 100° of flexion and the hip is externally rotated

Opening of the lateral compartment, to minimize the chance of iatrogenic injury to the lateral femoral condyle or tibial cartilage surfaces, is best achieved by placing the lateral aspect of the foot of the operative side on the anterior surface of the mid-tibia of the sterilely draped contralateral extremity, which allows the surgical technician or assistant to hold the foot in place (short arrow) in an optimal position (Figure 35.2)

Additional gapping of the lateral compartment can be achieved by simultaneously applying a downward force on the medial aspect of the knee

These two steps (securing the foot, varusizing the knee) may be performed selectively, only when sharp instruments are passed through the lateral compartment, so as to free the hands of the assistants for instrument passage and other functions

Establish a standard inferolateral portal just lateral to the lateral border of the patellar tendon and just proximal to the anterior horn of the lateral meniscus. For optimal viewing of the entire lateral compartment, the medial working portal should be established with the knee in the figure-4 position using a spinal needle under direct arthroscopic visualization (see Figure 35.2, long arrow)

The optimal position for the medial portal to allow instrumentation access to the entire lateral compartment is usually 1 cm proximal and 1 cm medial (long arrow) to the typical inferomedial portal position (Figure 35.3)

Alternatively, a standard inferomedial portal (see Figure 35.3, short arrow) can be established, with plans for creation of a secondary accessory portion in this proximal, medial position, if needed, later in the procedure

Finally, because the medial portal is often utilized as the viewing portal for portions of the procedure, consideration may be given toward creation of a secondary, accessory lateral portal that is 1 cm proximal to the typical inferomedial portal position. Specifically, this higher portal position may facilitate more atraumatic trimming of the anterior horn discoid meniscus tissue, particularly if this step is performed with arthroscopic, long-handled, thin meniscal knife (or “banana blade,” which is often used for precision trimming of excessive anterior horn tissue)