A surgical instrument for performing a meniscectomy comprising a pair of curved grooved guides of a shape corresponding to the periphery of the relatively inaccessible posterior portion of the meniscus, each guide being on a separate handle so that the two guides can be inserted intra-articularly respectively above and below the posterior portion of the meniscus to be peripherally detached. The two separate handles may then first be rigidly attached to each other and secondly to an overlying cutting blade frame. The cutting blade frame extends along the length of the grooved blade guide handles to the base of the two grooved guides and continuous upward after being bent through an angle of approximately 100.degree. with the cutting blade base mount. The continuation of this cutting blade frame supports and contains the flexible cutting blade which may be driven by any suitable force-producing means, for example, a mechanism operated on the screw-jack principle. When so driven the flexible cutting blade advances or proceeds along the grooves in the aforesaid curved grooved guides and detaches the periphery of the meniscus near its base intra-articularly along a curved path corresponding to the shape of said curved grooved guides. A surgical procedure for detaching a meniscus, using the above-mentioned instrument is described in detail.