Sesamoid Injuries: Diagnosis, Treatment, and Prevention

Sesamoid Injuries: Diagnosis, Treatment, and Prevention 

Fractures might not show up immediately on radiographs because it takes time for a bone’s repair work to appear.

Photo: Courtesy Dr. Dean Richardson

 Sesamoid injuries can be difficult to repair and even catastrophic; here’s what can go wrong and how to prevent it from happening

Two little bones sitting at the back of the fetlock both amaze and confound veterinarians. The sesamoids, as they’re called, anchor the suspensory apparatus that allows a horse’s foot and fetlock to move properly. Yet their location and anatomy make them vulnerable to injuries that can be difficult to repair and even catastrophic.

Given the sesamoids’ location, it isn’t surprising that high speeds can lead to fractures and soft tissue injuries. In a racehorse, for example, the fetlock can sometimes extend to the point that the sesamoid bones actually make contact with the ground. If the pressure is too great, those bones can shatter to a point that requires euthanasia.

“Horses have two proximal sesamoid bones on each limb,” says Jeff Blea, DVM, racetrack practitioner and past American Association of Equine Practitioners president. “They, together with the cannon bone and long pastern, make up the fetlock joint.” 

Blea explains that the sesamoids are surrounded by an intricate system of ligaments. The suspensory ligament begins at the top back of the cannon bone, runs down the cannon bone, and splits into two branches—one attaching to each sesamoid. Other ligaments connect the sesamoids to each other, and the distal sesamoidean ligaments extend down to the pastern bones. “If you look at it from a physiological standpoint, it’s a highly mechanical area,” says Blea. “It’s an area that is susceptible to increased tension, increased force, and increased pressure.”

While the sesamoids’ anatomy might make them seem like an accident waiting to happen, Emma Adam, BVetMed, Dipl. ACVIM, ACVS, PhD, who completed her PhD research at the University of Kentucky’s Gluck Equine Research Center and a former assistant to champion racehorse trainer Sir Michael Stoute, points out the remarkable way the bones facilitate a horse’s movement.

“Our patella is a sesamoid bone,” she says. “It is gliding over this amazing structure called our knee. In horses, the sesamoids provide a groove for these immensely strong flexor tendons, and they also provide mechanical support for this incredible unidirectional joint that sits in front of them. And they do both at the same time.”

Sesamoid bones are small—about the size of a walnut—and somewhat pyramidal in shape. That alone makes it difficult for surgeons or the body itself to repair a fracture. But Adam notes other challenges.

“Sesamoid bones have a really hard time,” she says, “because they don’t have the blood supply that many other bones do, they don’t have any musculature around them that can lend blood supply, and they don’t have a periosteum (the soft, protective tissue covering bone).”

Both blood supply and periosteum help bones heal. So without them the sesamoids are basically left to their own devices.

What Goes Wrong

Like any bone, sesamoids can fracture if overstressed. Because so many ligaments attach to them, any or all of those ligaments can also become injured. The more elements involved, the worse the prognosis.

Blea says when sesamoids fracture, they do so in one of three ways—apical (the top third), mid-body, or basal (at the bottom).

Veterinarians typically can remove an apical fragment arthroscopically (a minimally invasive surgery involving a fiberoptic camera), with a good prognosis for return to performance.

“The limiting factor regarding prognosis depends upon if the suspensory is involved and how much of that suspensory branch attachment is involved,” says Blea. “If the suspensory is damaged as well, your prognosis goes way down.”

Mid-body and compound (breaks through the skin) fractures usually result in a guarded to poor prognosis for return to performance, says Blea. Those horses sometimes can go on to successful second, less rigorous careers.

Blea is most pessimistic about basal fractures. “Some people are putting screws in there and having some success with them,” he says. “But the difficulty is that at the bottom of the sesamoid, you have those distal sesamoidean ligaments pulling, which creates more tension.”

Unfortunately, fractures can also occur catastrophically, where the sesamoids break into too many pieces to remove or reassemble. Many of these cases end in euthanasia. 

Some horses in this situation can be saved for breeding or companion purposes through arthrodesis, or fusing the joint, says Blea. They will never be athletically sound, but they can be pain-free.

Horses can also develop sesamoiditis, or bone inflammation. While too much stress on the joint can cause this, so can rapid growth in young, developing horses. 

Further research is needed to determine whether sesamoiditis correlates with an increased chance of future fractures. Other variables, including conformation, training regimens, and galloping speed, can be predisposing factors to sesamoiditis.

Age and breed also play roles. Adam says Warmbloods experience different types of sesamoid injuries than Thoroughbreds, likely because of body type differences and because Warmbloods destined for jumping, dressage, and eventing typically begin training later than racehorses.

“Warmbloods don’t get that many sesamoid injuries,” Adams says. “They typically get some changes related to osteoarthritis. They can get bony changes at the insertion of the suspensory ligament and the distal sesamoidean ligaments.”

If a Warmblood fractures a sesamoid, Adam says it is usually an apical or small basal fracture. “When you’ve got a horse doing a canter piaffe, you can understand the amount of strain being placed on the suspensory apparatus,” Adam says. “There is a lot of work going into that maneuver.”

Diagnosis Difficulties

Injuries can weaken bones before a fracture occurs. In addition, fractures might not show up immediately on radiographs because it takes time for a bone’s repair work to appear. Both of those things complicate sesamoid fracture diagnosis.

Sesamoids can fool people, says Blea. If a horse comes up lame, diagnostic anesthesia (blocking) might not pinpoint the problem. “A lot of times people think it’s a foot (problem),” says Blea. “They’ll do diagnostic anesthesia on the foot, and the horse will go sound. So they work on the foot, and a few weeks later the horse ends up with a sesamoid fracture.”

If diagnostic anesthesia does narrow the search to the fetlock and a possible sesamoid injury, yet the radiograph does not show anything, Blea recommends waiting and resting the horse 10-14 days and radiographing the area again, by which time a fracture might appear. 

“You often don’t diagnose (issues with) sesamoids until after they’ve fractured,” says Blea. “You may not see any inflammation, heat, or swelling in the bone,” prior to fracture.

The rehabilitation program in such cases typically starts with keeping the horse stallbound for up to 30 days and hand-walking him for up to 60 days. Blea recommends limited turnout after the hand-walking period so the horse can move around on his own, which aids the healing process. He then takes more radiographs four months after the injury to monitor healing.

Preventing Sesamoid Issues

The ideal solution to sesamoid injuries is preventing them in the first place. Blea and Adam stress the importance of establishing a good training foundation for any athletic horse before asking for top -performance.

“Sesamoids can undergo responses to training,” says Adam. Bone, muscle, and ligaments get fit at different rates, however, and training regimens need to take that into account. A horse also needs to be fit to avoid fatigue, which can lead to injury. Consistent, even footing and good shoeing practices are also extremely important for keeping the fetlock area sound.

“It’s important to have good medial to lateral (inner to outer) balance in the foot,” says Blea.

Other standard management techniques, including providing good nutrition, play equally important roles.

Perhaps the most significant thing any owner or trainer can do is constantly monitor for signs of sesamoid injury. “Due diligence by the trainer and the vet are essential,” says Blea. “Have conversations about the horse. Check the legs. Talk to the rider.”

Newer diagnostic methods can also aid greatly in prevention. Such options include nuclear scintigraphy (“probably the most common way we diagnose sesamoid problems,” says Blea, by visualizing bone remodeling), MRI, or CT.

Sue Stover, DVM, PhD, Dipl. ACVS, professor of anatomy, physiology and cell biology at the J.D. Wheat Veterinary Orthopedic Research Laboratory in Davis, California, and John Peloso, DVM, MS, Dipl. ACVS, owner, partner, and surgeon at the Equine Medical Center of Ocala, Florida, are researching sesamoid issues. Stover, in analyzing results from the post-mortem program in place at California racetracks, has determined that catastrophic fetlock failures account for more than 50% of the cases received. The work she is doing includes investigating radiographic techniques that could eventually lead to better and earlier diagnoses.

Peloso and others are finding that standing MRI, which does not require general anesthesia, is extremely helpful in diagnosing early sesamoid problems.  

In studies Peloso uncovered two major risk factors—increased density of sesamoid bones that makes them more brittle, and problems in the opposing fetlock (contralateral limb) that cause the horse to compensate on the brittle limb.

He says using MRI to look at bone density and also for early signs of injury in the contralateral limb could catch some sesamoid damage before fractures occur.

Peloso cited a paper by veterinarians in Newmarket, England, in which they used standing MRI in racing Thoroughbreds and identified cannon bone fracture pathology in 35.8% of study cases “pre-fracture” that they could not confirm -radiographically.

“The clinical signs of these injuries are very subtle and difficult to identify because they originate inside the bone below the cartilage surface,” says Peloso. 

Take-Home Message

High speeds coupled with suspensory apparatus anatomy can lead to sesamoid fractures and other injuries. Fracture diagnosis can be tricky because changes aren’t always evident when using traditional methods such as palpation and radiographs. Veterinarians have determined that nuclear scintigraphy, MRI, and CT are good diagnostic tools to detect problems. But nothing can prevent sesamoid injuries better than good management techniques and monitoring the fetlock consistently for the earliest sign of lameness or injury.

About the Author

Tracy Gantz

Tracy Gantz is a freelance writer based in Southern California. She is the Southern California correspondent for The Blood-Horse and a regular contributor to Paint Horse Journal, Paint Racing News, and Appaloosa Journal.

Short-, Long-Term Effects of Vibrating Platforms Studied

Short-, Long-Term Effects of Vibrating Platforms Studied 

In this study, all vibration therapy horses stood better and appeared to relax with each treatment, while control horses were restless by comparison.

Photo: Pam MacKenzie

Complementary therapies are steadily gaining popularity in the equine industry. While anecdotal evidence suggests some of these modalities might benefit horses, scientific evidence is lagging.

Take vibrating platforms, for instance. Equestrians across a variety of disciplines report improved performance and injury healing when their horses stand on them regularly. Still, research on the topic is in its infancy, and scientists haven’t confirmed whether time spent on a vibrating plate has any impact—positive or negative—on horses.

So, a team from Michigan State University (MSU), in East Lansing, recently set out to find answers. At the 2017 Equine Science Society Symposium, held May 30-June2, in Minneapolis, Minnesota, Chelsea Nowlin, a veterinary student at MSU presented the results of her undergraduate research. She worked under the direction of Brian Nielsen, PhD, PAS, Dipl. ACAN, professor of exercise physiology in MSU’s Department of Animal Science.

Nowlin and colleagues hypothesized that horses that underwent vibration platform treatment would have different physiologic parameters than those that did not.

The researchers used six Arabian geldings for the study. Two veterinarians specializing in sports medicine conducted a lameness exam on each horse and noted any potential lameness, gait deficits, and limited flexibility. Then, the team pair-matched the horses based on their age, sex, lameness scores, and stride length and assigned one horse from each pair to stand on a vibrating platform and the other to stand on an adjacent vibrating platform that was not turned on.

Nowlin said the researchers evaluated both short-term (or acute) and long-term effects. The acute test included one 30-minute vibration session, while the long-term phase consisted of treatment five days per week for three weeks. The same sports medicine veterinarians performed lameness exams on each horse immediately following their acute test and after the last treatment in the long-term phase.

Ultimately, the team found “no differences pre- and post-treatment between the vibration therapy and control groups in any of the parameters measured,” Nowlin said.

However, they did observe behavioral differences.

“Although quantitative behavior measurements were not taken, qualitative notes on behavior were made, and although subjective, it was consistently noted that behavior improved throughout the three-week prolonged phase,” she said. “All vibration therapy horses stood better and appeared to relax with each treatment, while control horses were restless by comparison.”

Nowlin said this finding could help explain why so many equestrians believe in vibration therapy’s positive effects even though none of the parameters measured changed after treatment.

Another reason owners might report an improvement in their horses’ conditions following long-term vibration plate use is, quite simply, time.

“Time is one of the greatest healers,” Nielsen told The Horse. “When people observe their horse getting better after using a vibrating platform for a period of time, it is quite likely due to healing that would have occurred regardless of whether the horses were being treated or not.”

He added that horses appearing to enjoy the vibrating platform after a few days “could provide evidence that it is having a benefit. … However, maybe it is simply like taking a baby for a car ride to get it to go to sleep. Possibly the vibrating motion of the platform works in a similar fashion in horses.”

Ultimately, he said, in this study, “regardless of the reason for horses appearing more sedate when standing on a vibrating platform, we saw no differences in lameness between those that were treated and those that were untreated.”

About the Author

Erica Larson, News Editor

Erica Larson, news editor, holds a degree in journalism with an external specialty in equine science from Michigan State University in East Lansing. A Massachusetts native, she grew up in the saddle and has dabbled in a variety of disciplines including foxhunting, saddle seat, and mounted games. Currently, Erica competes in eventing with her OTTB, Dorado.


Mario Gutierrez
August 30Del Mar

Dreamarcher Wgt-122 Race 2 Allowance Optional Claiming $100,000
Arunachala Wgt-120 Race 5 Maiden Special Weight
It’s About Alex Wgt-118 Race 6 Generous Portion S.
September 1Del Mar

Mis Viola Wgt-123 Race 2 Starter Optional Claiming $50,000
Shakti Wgt-121 Race 5 Allowance Optional Claiming $40,000
Tangeline Wgt-124 Race 6 Maiden Special Weight
Cowboy Wgt-124 Race 8 Claiming $32,000

August 27 – Del Mar
Beau Square finished 2nd beaten 2 1/2 lengths Race 3 Chart
Turnaround finished 3rd beaten 1 lengths Race 7 Chart
True Valor finished 6th beaten 5 3/4 lengths Race 8 Chart

Munny Spunt Awarded Torrey Pines Victory Via Disqualification

Munny Spunt (Outside) © Benoit Photo

Munny Spunt, claimed for $25,000 June 30 at Santa Anita, gave her new owners a quick return on their investment as she was awarded victory Sunday in the $100,000 Torrey Pines Stakes when Del Mar’s stewards disqualified original winner Zapperkat for stretch interference.

Munny Spunt, with Drayden Van Dyke in the saddle at odds of 18-1, was rallying powerfully on the outside and seemingly on her way to win when Zapperkat, under Norberto Arroyo, Jr., bore out sharply, bumping Munny Spunt off stride. Zapperkat reached the wire a head in front, but was disqualified and placed second for her infraction.

Bernina Star, a 25-1 longshot, was third, three lengths farther back, with Chocolate Coated fourth in the field of seven three-year-old fillies.

Paradise Woods, the 1-5 favorite under Flavien Prat, stumbled in breaking from the gate, rushed up to the prompt the pace into the far turn but then came up empty in the stretch, finishing sixth. Paradise Woods, winner of the Santa Anita Oaks brilliantly last April, was making her first start since running eleventh as the favorite in the Kentucky Oaks May 5.

Munny Spunt, a $1,000 supplemental entry to the Torrey Pines, returned $38.60, $14.20 and $9.40 while earning $60,000. After being claimed, she won a $32,000 claiming event July 29 at Del Mar and then finished fourth in the Grade III Rancho Bernardo Handicap Aug. 13. The win was her fifth in 13 career starts.

The victress, a Florida-bred daughter of Munnings, is owned by ERJ Racing, Fuller and Robershaw and trained by Doug O’Neill.

Runner-up Zapperkat paid $6.20 and $5.40, while third-place Bernina Star returned $10.80.

DRAYDEN VAN DYKE (Munny Spunt, winner via DQ) – “She broke OK and I just let her get comfortable. She was taking me where I wanted to be. About the three-eighths (pole) we got serious. When we got into the stretch, I got hit (by Zapperkat) once; then I got hit again. When that happened I knew I might have a chance to be given this one. When they knock you off balance, then usually something happens. This is the first time I’ve won a graded stakes on a disqualification.”

NORBERTO ARROYO, JR. (Zapperkat, placed 2nd by DQ) – “She surprised me (by her swerves outside). She’s never done that before (Arroyo has ridden her in her previous four starts). She really just got away from me.”

SANTIAGO GONZALEZ (Bernina Star, third) – “Good race for my filly. She broke well and she ran well. No complaints.”

FLAVIEN PRAT (Paradise Woods, sixth) – “Everything went wrong. She broke badly, then she got very aggressive. At the three-eighths (pole) she finally took a breath and settled down. But then when we went into the stretch, I was totally out of horse.”

DOUG O’NEILL (Munny Spunt, winner) – “She has got such a big heart. We knew that Paradise Woods was a super good filly, but it was in our own backyard, we knew our filly loved the track and we thought we’d take the chance. (Decision to supplement) It’s always easy after the fact but we thought we’d take a chance and it worked out this time. (Win by DQ) I hate to win on a DQ like that but our filly never got to run the last 16th of a mile. We hate to win like that, but we’ll take it. ”

FRACTIONS: :22.66 :47.45 1:11.98 1:24.45 1:37.20

The stakes win was the second of the meet for rider Van Dyke, but his first in the Torrey Pines. He now has nine stakes wins at Del Mar.

The stakes win was the second of the meet for trainer O’Neill, but his first in the Torrey Pines. He now has 36 stakes wins at Del Mar.

The winner, who was supplemented to the race at a cost of $1,000, is owned by ERJ Racing (Eric Johnson of Cherry Hill Village, CO); John Fuller (Culver City, CA); Richie Robershaw (San Diego, CA); Steve Rothblum (Arcadia, CA), and trainer Doug O’Neill (Santa Monica, CA).

Del Mar Daily Results and Activity


Sunday, August 27
Race# Race Type Purse
Race 1 Claiming – $8,000 $20,000 Overnight Overnight
Race 2 Maiden Claiming – $50,000 $30,000 Overnight Overnight
Race 3 Allowance Optional Claiming – $40,000 $62,000 Overnight Overnight
Race 4 Claiming – $32,000 $39,000 Overnight Overnight
Race 5 Allowance Optional Claiming – $40,000 $62,000 Overnight Overnight
Race 6 Torrey Pines S. $100,000 Overnight Overnight
Race 7 Maiden Special Weight $60,000 Overnight Overnight
Race 8 Allowance Optional Claiming – $75,000 $62,000 Overnight Overnight
Race 9 Starter Allowance – $50,000 $35,000 Overnight Overnight
Race 10 Starter Allowance – $50,000 $35,000 Overnight Overnight

Early Entries

Friday, September 1 Overnight
Race# Race Type Purse
Race 1 Maiden Claiming – $32,000 $24,000
Race 2 Starter Optional Claiming – $50,000 $48,000
Race 3 Maiden Special Weight $60,000
Race 4 Maiden Special Weight $60,000
Race 5 Allowance Optional Claiming – $40,000 $62,000
Race 6 Maiden Special Weight $60,000
Race 7 I’m Smokin S. $100,000
Race 8 Claiming – $32,000 $34,000

Golden Gate Daily Results and Activity


Sunday, August 27
Race# Race Type Purse
Race 1 Maiden Claiming – $8,000 $8,000 Overnight Overnight
Race 2 Claiming – $6,250 $10,000 Overnight Overnight
Race 3 Waiver Claiming – $6,250 $11,000 Overnight Overnight
Race 4 Claiming – $6,250 $9,000 Overnight Overnight
Race 5 Starter Allowance – $4,000 $10,500 Overnight Overnight
Race 6 Maiden Special Weight $31,000 Overnight Overnight
Race 7 Starter Allowance – $4,000 $10,500 Overnight Overnight
Race 8 Allowance $27,000 Overnight Overnight
Race 9 Starter Allowance – $40,000 $17,000 Overnight Overnight

Early Entries

Friday, September 1 Overnight
Race# Race Type Purse
Race 1 Maiden Claiming – $25,000 $14,000
Race 2 Maiden Claiming – $12,500 $9,000
Race 3 Maiden Claiming – $32,000 $15,000
Race 4 Starter Allowance – $40,000 $17,000
Race 5 Maiden Claiming – $32,000 $15,000
Race 6 Starter Allowance – $40,000 $17,000
Race 7 Allowance Optional Claiming – $62,500 $29,000

Saratoga Daily Results and Activity


Sunday, August 27
Race# Race Type Purse
Race 1 Claiming – $20,000 $39,000 Overnight Overnight
Race 2 Maiden Claiming – $75,000 $56,000 Overnight Overnight
Race 3 Claiming – $40,000 $47,000 Overnight Overnight
Race 4 Claiming – $40,000 $62,000 Overnight Overnight
Race 5 Maiden Special Weight $83,000 Overnight Overnight
Race 6 Maiden Special Weight $73,000 Overnight Overnight
Race 7 Allowance $75,000 Overnight Overnight
Race 8 Starter Allowance – $50,000 $55,000 Overnight Overnight
Race 9 Smart N Fancy S. $100,000 Overnight Overnight
Race 10 Maiden Special Weight $83,000 Overnight Overnight

Early Entries

Thursday, August 31 Overnight
Race# Race Type Purse
Race 1 Handicap $70,000
Race 2 Maiden Claiming – $30,000 $35,000
Race 3 Allowance Optional Claiming – $25,000 $75,000
Race 4 Allowance Optional Claiming – $40,000 $78,000
Race 5 Maiden Special Weight $73,000
Race 6 Allowance $85,000
Race 7 Maiden Special Weight $73,000
Race 8 Allowance $75,000
Race 9 P. G. Johnson S. $100,000
Race 10 Claiming – $16,000 $32,000

Woodbine Daily Results and Activity


Sunday, August 27
Race# Race Type Purse
Race 1 Maiden Claiming – $20,000 $21,700 Overnight Overnight
Race 2 Starter Allowance – $20,000 $32,600 Overnight Overnight
Race 3 Claiming – $10,000 $21,000 Overnight Overnight
Race 4 Claiming – $25,000 $32,600 Overnight Overnight
Race 5 Maiden Claiming – $40,000 $34,000 Overnight Overnight
Race 6 Maiden Special Weight $61,000 Overnight Overnight
Race 7 Allowance $61,000 Overnight Overnight
Race 8 Ontario Colleen S. $125,000 Overnight Overnight
Race 9 Claiming – $6,250 $16,000 Overnight Overnight
Race 10 Claiming – $20,000 $24,100 Overnight Overnight
Race 11 Maiden Claiming – $10,000 $18,700 Overnight Overnight


HASTINGS NEWS – By Greg Douglas


 Vancouver, B.C. (August 27/17) — Sohen Gill, a staunch supporter of the racing industry for as long as anyone can remember, was struck with a thought when he saw BC Sports Hall of Fame members Dale Walters (boxing) and Archie McDonald (media) huddled in a corner in deep conversation at Hastings recently.

“We have so many legends from our local sports community who are regulars at the track maybe one day we should have them all out as guest decorators,” Gill suggested. “It sure would bring back a lot of memories.”

As humble as he is, Gill neglected to include himself in the group. In fact, it was in May of 2009 when Gill, McDonald and Chris Loseth were all inducted into the Hall of Fame at the Banquet of Champions in downtown Vancouver.

Loseth was being acknowledged for his illustrious career as Hastings’ leading jockey an unprecedented eight times and 3,668 career wins over a span of 30 years and more than 26,000 mounts.

Sohen’s induction was inspired by his long and colorful career in local lacrosse as a player, coach, manager and Western Lacrosse Association commissioner as well as president of the British Columbia Lacrosse Association.

His dedication did not go unrecognized. He was named winner of the Tom Gordon ‘Mr. Lacrosse’ award three times and was inducted into the Canadian Lacrosse Hall of Fame in 2005.

The story that simply must be repeated about Gill appeared in the 2009 BC Sports Hall of Fame official program, penned by Curator Jason Beck.

“In December 1990, Sohen Gill’s life changed forever,” Beck wrote. “As a lieutenant firefighter, he was on the roof surveying a burning Kitsilano building when it disintegrated, plunging him into a scorching inferno.  Miraculously, he dove out a window and survived.  Following weeks of intensive care and the burn unit, then nearly three years of rehab, he recovered.

“Some might scale back their activities after such an experience. Gill increased his lacrosse involvement, feeling he’d been granted a second lease on life.”

Gill speaks of legendary figures who visit Hastings Racecourse on a regular basis. None is more of a legend than the man himself.