The intercondylar notch is the deep space between the two rounded ends (condyles) of the femur bone (thighbone).

The narrow intercondylar notch
A narrow intercondylar notch may predispose to cruciate ligament tears. It is often widened with a rotating burr during anterior cruciate ligament reconstruction in order to prevent obstruction of the new ligament with formation of a cyclops lesion.
CLINICAL PUBLICATIONS
The Importance of the Intercondylar Notch in Anterior Cruciate Ligament Tears. Fernández-Jaén T, López-Alcorocho JM, Rodriguez-Iñigo E, Castellán F, Hernández JC and Guillén-García P. Orthop J Sports Med. 2015 Aug; 3(8): 2325967115597882.
Risk factors for Anterior Cruciate Ligament injury in skeletally immature patients: analysis of intercondylar notch width using Magnetic Resonance Imaging. Domzalski M, Grzelak P and Gabos P. Int Orthop. 2010 Jun;34(5):703-7. doi: 10.1007/s00264-010-0987-7. Epub 2010 Mar 24..