Tissue healing within the stifle can take up to a year and occurs in three phases. The first is the inflammatory phase. This is an acute vascular response that occurs in the three to five days immediately following the injury. Then the reparative stage begins, lasting two to six weeks. Here, collagen production and matrix synthesis occur.
The goal of this phase is to promote tissue healing in a way that will help the horse have full use of the injured joint.
“Fundamentally, what you want to do is have the tissue looking as close to normal as possible,” said Daglish. “An ideal example of that is the superficial digital flexor tendon, where you want a parallel alignment of fibers and, quite often, if they are left to their own devices, they just end up a lump of ugly-looking tissue. In the stifle we are aiming to achieve the same thing, which is parallel fiber alignment, restoration of as normal an appearance as possible, and minimal scar tissue, so that the function can be as good as possible when the horse gets back into work.”
Lastly, the remodeling phase starts at around two to three weeks post-injury and lasts about a year. The collagen fibers develop and cross-link, and collagen fibers reorientate.
When planning a rehabilitation program for a stifle, Daglish said it’s critical to consider the amount of damage, the structures involved, chronicity of the injury, and clinical signs.
Initial Steps in Rehabilitation
The first stage of rehabilitation might include surgical debridement (cleanup) of the injured structure within the joint, if needed. Veterinarians can administer biologic therapies at this point, including stem cells, interleukin-1 receptor antagonist protein (IRAP), autologous protein solution, and platelet-rich plasma (PRP). They can also introduce systemic anti-inflammatories as well as topical anti-inflammatories, such as dimethyl sulfoxide (DMSO). Cryotherapy (icing) can also be useful, said Daglish.
Healing Stifle Joint Tissue
Controlled exercise can help rehabilitate the damaged tissue. Introduce joint loading gradually, beginning with hand-walking (starting at five minutes twice daily and building up to 40 minutes). You can also slowly introduce long-reining, ponying, and ground poles. Avoid mechanical horse walkers initially, Daglish said, because they require the horse to move in repetitive circles. While you can walk the horse on gentle slopes, avoid steep hills, tight turns, and deep footing, which can destabilize the joint.
Ideally, you’ll want to implement physical therapy activities four to five days a week. Limb-specific stretches can improve the horse’s quadriceps, hamstrings, and gluteal muscles. Balance pads, used for five minutes daily, provide micromotion that helps strengthen the joint capsule and build the horse’s proprioception.
Laser therapy, used every other day for several weeks (four to six, ideally), can increase healing but should not be used over surgical implants.
Strengthening the Stifle and Remodeling
Once the horse’s stifle healing is at a suitable point, as determined by follow-up examinations, the veterinarian might clear the horse to begin the ridden portion of the rehab program.
Before introducing ridden work, be sure you’ve already worked up to 40 minutes of daily hand-walking on a firm surface. At the start of tack-walking, reduce your sessions to 20 minutes, and build back up gradually.
Ideally, reintroduce trot and canter work from the ground, before moving under saddle. To avoid tight turns, perform trot work while ground driving, on a dry treadmill, or while ponying alongside another horse. Start with short five-minute trot sessions, and gradually build up to 20 minutes. Then begin incorporating canter work. As with the walk and trot, increase the amount canter work slowly. During Week 1 of canter, one or two laps around the arena in each direction is sufficient, still avoiding tight turns if possible. Then, increase to five minutes of canter, with intermittent trot and walk breaks.
When setting up poles for a rehabilitating horse to walk over, set them at related distances that encourage range of motion in flexion and extension. Over time, increase the number of poles and add height (up to 12 inches).
Generally, you can introduce sport-specific training, such as jumping, six to eight months into rehab, depending on the rate of healing. Small paddock turnout can begin once the horse is cantering soundly.
Expect to see some back and forth in terms of progress, she said. For example, if a horse is newly allowed out to small paddock turnout and runs off, it is not unusual for him to have a setback. If needed, use a sedative for turnout or a restraint method while hand-walking to help prevent this. If a setback occurs, Daglish recommended applying cryotherapy.
“I will sometimes use cryotherapy in horses who have had little flare-ups,” she said.
“I am not necessarily thinking of horses who have gone very lame, but the ones who have just not been quite as good as they have been now that we’ve upped the work.”
Consider Underwater Treadmill for Stifle Rehab
Underwater treadmills can be added to stifle rehabilitation programs after about two weeks. If the horse needed surgical intervention, delay underwater treadmill work for about 21 days post-surgery.
The water depth should reach the horse’s shoulder, which reduces stifle loading by 30%. Sessions should start short, only lasting five to 10 minutes. Over time, they can increase to 20 or 30 minutes, depending on the horse’s fitness and rate of healing.
Using an underwater treadmill up to five days a week can increase how quickly the joint heals, while reducing unnecessary loading of the internal structures of the joint.
Monitoring Stifle Injuries
Have a veterinarian reevaluate the horse prior to moving onto each stage of rehabilitation. While useful, radiographs and ultrasound might not be necessary at every check-in to determine progress, unless further deterioration is a concern.
Following guided rehabilitation gives the horse the best potential outcome. Making sure owners are aware of the management modifications and long-term game plan helps improve the horse’s prognosis for a full return to his previous use, Daglish said.
Between icing, laser, and physical therapy, owners must be aware of the time proper rehabilitation takes. “The total time per day is not unsubstantial,” said Daglish, “and it’s a team approach.”
Horses with stifle injuries have gone on to compete in sports such as eventing, reining, dressage, show jumping, and more, provided their healing is sufficient.
Of course, not all rehabilitations will be successful. “This might be our biggest frustration as veterinarians,” Daglish said. “We might get a horse all the way through its program only for the leg to reinjure on your last gallop, or you might do your first event of the season and the horse comes back lame.”
It’s important to look at everything going on in the horse, she said, including secondary concerns caused by the stifle injury.
“The whole-horse approach is invaluable” to give the horse the best chance at success, she added. “If you’re just (focusing on) the stifle, you’re going to fail your rehab. Horses need to be looked at as a big picture, and if you just target the stifle injury, you will not succeed.”