The Chute of the Knees is the preferred descent shortcut on the way from the upper Arista del Sol back towards Grupo de los Cien Hut and La Joya trailhead.
Although in rare consolidated snow conditions the chute may be followed up, normally its loose sandy scree is only good for glissading down. Therefore, the preferred approach is from the summit of Iztaccihuatl (or for from the points between the summit and Las Rodillas aka the Knees). That's the direction I am going to use in the detailed description.
The descent gully is also known as Canalón de los Totonacos, after an Indian tribe famous for their flight-dance in which the Fliers are suspended upside down from a pole-top. I guess the name is meant as a warning, lest you loose your footing and end up performing a Totonaco pirouette :) !
From the South Summit, follow the ridge South across the false summit (17,027 ft) and left (SE) on low ridge of loose volcanic soil, to a convenient point for dropping to the glacier plateau of La Panza. Cross the glacier to the South and gain the ridge of Hill 16,700 (which should properly be dubbed the Pubic Hill since it marks the end of the Belly and the beginning of the Legs of the Sleeping Lady). The very top of this hill, as well as the entire next hill to the South, are bypassed on the East slopes (on the left). From the 2nd col past the Pubic Hill, ascend the ridge to the Knees and the ruins of Dr Luis Mendez Shelter (sections of class III rock).
From the aluminum frame of the ruined hut (16,570 ft, N 19° 09.740 W 98° 38.219 WGS84), leave the ridge line and drop to the right (West). Angle to the right at first, until the wide gully opens below. Keep glissading until the left bank of the gully opens wide (it would appear that the coloir cliffs out further below, which it actually doesn't, but it's time to leave it anyway!). Exit to the left and angle left and down to the white hulk of Grupo de Los Cien Hut (15,470 ft, N 19° 09.398 W 98° 38.226 WGS84)
From this point you are back on the standard Arista del Sol trail. Gain the ridge to the South-East of the Shelter, cross the ridge to the East side for the descending traverse of the sandy slopes to Portillo (col) de los Pies (14,874 ft). Cross to the West side for a gentle traverse to the second Portillo (14,437). From the South end of the 2nd col, the trail descends on the East side again, then traverses with a very minor altitude gain to Anteportillo ("preliminary col", which is the nearest ridge crossing to the trailhead). Follow a well defined trail on a sweeping traverse of West-facing grassy slopes to the road.
Sturdy footwear, ice axe or trekking poles for glissading, preferably gaiters to keep the scree out of your boots. Depending on weather conditions, crampons may be essential.