A partial meniscectomy may leave the outer rim intact.
The all-important outer meniscus rim
The outer rim is the most important part when it comes to absorbing and deflecting the vertical forces going through the knee.
If the damaged part has to be removed, the surgeon will try to at least retain the outer rim.
The current controversy about meniscal trimming
There is ongoing controversy about whether trimming of a bit of degenerative meniscus is better than doing nothing and just relying on physiotherapy.
"....A central tenet of managing meniscal pathology is to preserve tissue whenever possible....patients who fail nonoperative treatment should be counseled regarding the risks of [arthroscopic partial meniscectomy] before proceeding to surgical management...."
"....There have been several landmark multicenter randomized controlled trials (RCTs) studying the outcomes of [arthroscopic partial meniscectomy (APM) ] compared to [physiotherapy] or sham surgery in symptomatic degenerative meniscal tears. These .... failed to identify substantial benefits of APM over nonoperative treatment or even placebo surgery...."