Here is a brief description of the tendon Fendi has lost (common/long (hind limb) digital extensor tendon).  I suggest we all read the full page here, but her injury is the paragraph i underlined here.

Evaluating The Injury

The first step in evaluating a tendon laceration is determining the structures involved and the degree to which they are involved. Location on the leg is important.

Remember the tendon sheaths? Lacerations involving the tendon sheaths can be of special concern and need to be noted. If the laceration is in the area of a joint, there always is concern. (For the purpose of this article, we will focus on lacerations involving only the tendons.) If the nature of the laceration is sharp, the evaluation often is easier as the structures involved are well-defined vs. lacerations associated with a dull cutting and/or tearing where little defined structure remains.

When the flexor tendons are injured, there are some characteristic alterations in limb posture that occur depending on what structures are affected. Working from superficial to deep, if only the skin is involved, consider yourself and your horse extremely lucky. If the superficial digital flexor tendon is only partially involved, there generally is no alteration to posture. However, if the superficial digital flexor tendon is completely transected, the fetlock has lost some of its support structure and the fetlock will "drop" some or become closer to the ground when compared to the normal leg. This drop can be subtle, since the main fetlock support structure is the suspensory ligament. The important indicator is that the foot remains flat on the ground if only the superficial digital flexor tendon is
transected.

When the deep digital flexor tendon is lacerated, the toe often will "pop up" off the ground as the foot rocks back slightly on the heel. Remember that the deep digital flexor tendon courses down the back of the leg, gliding around the fetlock joint, all the pastern joints, and the coffin joint, to attach on the mid-bottom of the coffin bone (P3). It is this structure that yields the clinical sign of a ruptured or lacerated deep digital flexor tendon since it is the tension on the tendon that pulls and holds the foot flat on the ground. If the suspensory ligament is involved or transected, the fetlock's ability to support weight is greatly diminished, and the back of the fetlock significantly drops closer to or actually touches the ground.

On the other side of the leg are the extensor tendons, with the common digital extensor the main extensor tendon in the forelimb and the long digital extensor tendon the main extensor tendon in the hind-limb. A loss in the integrity of the extensor tendons has little effect on weight bearing, but does affect the ability of the horse to advance the limb properly during motion. Given that the extensor tendons course down the cannon bone, attaching to the dorsal (front) surface of the pastern (P1 and P2) and coffin bone, their effect is to extend the fetlock joint or pull the foot and pastern forward during movement.

So, a horse with a transected extensor tendon generally has trouble advancing the foot and will drag the toe, knuckling over onto the dorsal surface of the fetlock. Some horses quickly learn to "flip" the foot forward so that their weight-bearing surface is parallel to the ground as the foot lands.

I am attaching (not inserting) pictures before and after, PLEASE NOTE before pics are not for weak stomach..after pic is last one where she is sutured.

In these pics, we we were on day 3 of rehab (first week of June 2010), she was being medicated with bute, penicillin 2xday, tribrissen paste, in a pvc splint to support her weight the pvc is also attached to her hoof by drilling a hole in the hoof and wiring the splint to it, to be sure the hoof is & stays in forward position. 

I will continue her story thoughout in date order..

I hope this will help save just one horse by posting..  I will also post a discussion about the amnion used to help her heal, truly amazing!!