Degenerative joint disease is a common yet complex condition among equine athletes, and managing it effectively often requires veterinarians to integrate multiple techniques.
During the Dec. 8 Sunrise Session “Tackling Degenerative Joint Disease: Real-World Case Studies,” presented by American Regent Animal Health, at the 2024 American Association of Equine Practitioners (AAEP) Convention, Sherry Johnson, DVM, MS, PhD, DACVSMR, senior partner at Equine Sports Medicine in Pilot Point, Texas/Scottsdale, Arizona, and Kelly Zeytoonian, DVM, MBA, CERP, owner of Starwood Equine Veterinary Services in Redwood City, California, described their multimodal approach to supporting a wide variety of equine athletes.
The Recovering Athlete
Background
The first case Johnson described was a 5-year-old Quarter Horse mare that competes in Western all-around events at Select and Level 4 Open (national) levels.
When the mare first developed clinical signs, she presented with a 3/5 left hind lameness which localized about 30% to distal intertarsal (DIT) analgesia and 70% to a combination of tarsometatarsal joint (TMT) and DIT intra-articular analgesia. Previous hock injections yielded minimal improvements, and ultrasound of the left hind proximal suspensory ligament was unremarkable.
Hock radiographs revealed significant degenerative changes including subchondral bone sclerosis and lysis through the DIT joint, bridging osteophyte formation, and lysis and sclerosis through the distal tarsal interligament fossa.
Because the horse did not improve with rest and injections and the hock radiographs showed significant signs of advanced degenerative joint disease, Johnson recommended an MRI to get a more comprehensive diagnostic evaluation. MRI evaluation diagnosed moderate subchondral bone demineralization of the central tarsal bone extending to the level of the proximal intertarsal joint, as well as severe lysis and partial ankylosis (fusion) of the DIT joint.
Most worrisome was that the subchondral bone demineralization of the central tarsal bone was located within an area often prone to fracture. “Had we just injected this mare, shock-waved her and rolled on, the mare could have developed a slab fracture,” said Johnson.
Management Plan
Due to the extent and severity of the demineralization of the central tarsal bone, surgically facilitated distal tarsal ankylosis was not a viable therapeutic option for this mare. Therefore, Johnson had to employ a multimodal rehabilitative approach.
The mare spent a significant amount of time at Johnson’s rehab clinic, where she engaged in blood flow restriction (BFR) training, underwater treadmill work, proprioception exercises, resistance band training, and balance exercises. In addition, said Johnson, “the use of Adequan i.m.® (polysulfated glycosaminoglycan) became pivotal as part of this mare’s multimodal rehabilitation.”
When explaining her decision to use Adequan i.m. for this case, Johnson cited a 1993 study by Burba et al., which detected Adequan i.m. in horses’ cartilage and subchondral bone 96 hours following intramuscular injection. (Please see Brief Summary, including Important Safety Information for Adequan i.m., below.)
Outcome
Johnson reported this mare has gone on to set the NSBA World Championship Show record in Open Senior Western Riding and won the Open Level Western Riding at the AQHA World Show. She continues to compete successfully at the national level.
“This was not a Cinderella story, and I’m not here to tell you this mare is perfect every single day,” Johnson said. “But I do feel like with the intervention, with the multimodal approach, we were able to turn this mare around.”
The Actively Competing Athlete
Background
The next case Johnson described was a 14-year-old Quarter Horse gelding competing in youth Western all-around events. This horse had chronic osteoarthritic changes in his left carpus, including osteophyte formation on the medial aspect of the radiocarpal joint, bone sclerosis, and chronic joint capsule enthesopathy associated with wear and tear. Clinically, this horse had competed successfully with a long athletic career and seemed to like his job. His osteoarthritic changes had been managed for some time with corticosteroid injections and IRAP therapy.
Management Plan
Johnson employed a multimodal (biologic) intra-articular support program for this horse alongside shockwave therapy. In addition to continuing with therapeutic corticosteroids and IRAP, she recommended the use of Adequan i.m.® (polysulfated glycosaminoglycan).
Johnson’s decision to use Adequan i.m. for this case was supported further by Frisbie et al. (2009), which showed improved synovial membrane vascularity and less subintimal fibrosis associated with PSGAG treatment.
“What I want to provide is that consistent systemic support of articular cartilage health alongside these staged intra-articular therapies,” Johnson said. The goal in doing so is to block degradative enzymes to better maintain the horse’s long-term joint health.
The Unknown Athlete
Background
The first case Zeytoonian described was a 17-year-old Friesian-cross mare being considered for purchase for Training Level dressage. These were first-time horse buyers looking for a safe mount for their junior amateur daughter.
This horse had a history of hock and pastern injections every six months for multiple years with her current owner. During the prepurchase exam (which was not conducted by Zeytoonian), she was positive to distal forelimb and upper hind-limb flexions and was graded 1/5 lame on her left front.
These findings raised several questions with the potential buyers: What does this mean for the horse’s long-term soundness? What will this mean for my daughter? How much money will I have to spend on management for this horse? Should I buy this horse?
Without urging the buyers in one direction or the other, she reminded them this is an older horse that has been there, done that and will be safe for their kid. She told them just because the horse has had injections every six months doesn’t necessarily mean she needs them in perpetuity, especially with the change in workload. Ultimately, the buyers moved forward with purchasing the horse.
Management Plan
Zeytoonian’s approach for this horse was to pause her corticosteroid injections, introduce her to the new program, and start her on systemic joint support with Adequan i.m.® (polysulfated glycosaminoglycan) to manage her arthritic changes. “My approach is always investing in systemic support,” Zeytoonian said.
Outcome
Zeytoonian reported the horse has now been with the junior rider for two years and has not needed her previous joint injections. She attributes this success to a change in management, a change in expectations for riding level, and a systemic approach to joint support.
The Hard-to-Treat Athlete
Background
The second case Zeytoonian described was a 17-year-old Appendix Quarter Horse gelding used as an advanced lesson horse with a history of chronic shifting hind-limb and forelimb lameness. The horse had done well with hock injections every six months for the past seven years. However, he eventually developed bony callouses in the hocks, which made them more difficult to treat.
At first, Zeytoonian shifted from treating the hocks with corticosteroids to Pro-Stride® APS. The horse’s condition ultimately progressed to the point of requiring radiographs to guide the injections, which wasn’t financially feasible for the owner. To complicate the situation further, the horse became lame on his left front when they were no longer able to treat the hind end.
Management Plan
The goal for this horse was to find an attainable, affordable solution that would allow him to continue in the owner’s lesson program. Zeytoonian dispensed Adequan i.m.® (polysulfated glycosaminoglycan) to the owner, and she gives the horse a full series every four to six months for her DJD. The horse also receives Osphos® (clodronate injection) therapy and Equioxx® (firocoxib).
Outcome
Zeytoonian reported that two years later, this horse is still part of the lesson program and happy in his job.
Why Adequan i.m.?
Johnson and Zeytoonian have both had success incorporating Adequan i.m. into their multimodal programs to help manage difficult cases of degenerative joint disease.
“We feel really comfortable and supportive of Adequan i.m. being part of our program because we know that we get those levels of HA (hyaluronic acid) production within the synovial fluid and the cartilage within two hours after IM injection,” said Zeytoonian. “It doubles within two days and then remains there for four days.”
Johnson said the frequency with which she administers Adequan i.m. is case-dependent. Generally, she recommends giving the horse a full course of treatment twice per year with monthly maintenance injections in between.
Zeytoonian’s goal in prescribing Adequan i.m. is to implement timely intervention before horses diagnosed with degenerative joint disease start to feel sore. “Just like they need their flu/rhino vaccine every six months, they get a reminder that their horse is due for Adequan i.m. every six months,” she said about this group of patients.
BRIEF SUMMARY: Prior to use please consult the product insert, a summary of which follows: CAUTION: Federal law restricts this drug to use by or on the order of a licensed veterinarian. INDICATIONS: Adequan® i.m. is recommended for the intramuscular treatment of non-infectious degenerative and/or traumatic joint dysfunction and associated lameness of the carpal and hock joints in horses. CONTRAINDICATIONS: There are no known contraindications to the use of intramuscular Polysulfated Glycosaminoglycan. WARNINGS: Do not use in horses intended for human consumption. Not for use in humans. Keep this and all medications out of the reach of children. PRECAUTIONS: The safe use of Adequan® i.m. in horses used for breeding purposes, during pregnancy, or in lactating mares has not been evaluated. For customer care, or to obtain product information, visit www.adequan.com. To report an adverse event please contact American Regent, Inc. at 1-888-354-4857 or email pv@americanregent.com.
References
- Burba, D. J., Collier, M. A., Default, L. E., Hanson-Painton, O., Thompson, H. C., & Holder, C. L. (1993). In vivo kinetic study on uptake and distribution of intramuscular tritium-labeled polysulfated glycosaminoglycan in equine body fluid compartments and articular cartilage in an osteochondrial defect model. Journal of Equine Veterinary Science, 13(12), 696–703. https://doi.org/10.1016/s0737-0806(06)81570-4
- Frisbie, D. D., Kawcak, C. E., McIlwraith, C. W., & Werpy, N. M. (2009). Evaluation of polysulfated glycosaminoglycan or sodium hyaluronan administered intra-articularly for treatment of horses with experimentally induced osteoarthritis. American Journal of Veterinary Research, 70(2), 203–209. https://doi.org/10.2460/ajvr.70.2.203
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