Superficial Digital Flexor Tendinitis

After creating a training regimen that provides support for the racehorse's cardiovascular, musculoskeletal, energetics, biomechanics, thermoregulation, and nutrition the speed and endurance required to compete in a racing can still result in unplanned and unforeseen injuries. Twelve hundred pounds of racehorse impacts the ground with tremendous concussive forces during the gallop where one leg at a time hits the ground. The joints of the lower limb, particularly the fetlock joints, hyperextend on impact to the point where the distal ankle can touch the ground (Berkland, 2020). Track substrates are scientifically engineered to mitigate these forces, but not always successfully (Berkland, 2020). Injuries to the tendons that run caudally to the cannon bone are unfortunately common. An example is superficial digital flexor tendinitis (Figure 1). The superficial digital flexor tendon is located in the fore and hind limbs and runs along the back of the cannon bones and connects the short pastern to the coffin bone (LLC, HorseDVM). The superficial digital flexor tendon is responsible for the stabilization and support of the fetlock joint. (LLC, HorseDVM). A great deal of weight is supported by this very small cross-sectional area of flexor tendons, which is vulnerable to injuries. Tendinitis occurs when the natural arrangement of the fibers is disrupted, inflamed, edematous, and hemorrhagic (LLC, HorseDVM). This injury can happen suddenly resulting from a fall or a strike from another limb or gradually from being overworked which can progressively weaken the tendon (LLC, HorseDVM). Clinical signs of superficial digital flexor tendinitis are swelling behind the cannon bone, heat, pain upon touch, refusal to switch leads, and lameness within two to three days following the injury (LLC, HorseDVM). Lameness exhibited can be moderate, transient, or intermittent.

Superficial Digital Flexor Tendon
Figure 1. Superficial Digital Flexor Tendin

Treatment should begin immediately by reducing inflammation, limiting lesion expansion, and stall rest. Thirty minutes of cold-water therapy several times a day should be applied to the injury. Cold therapy includes cold-water hose and ice boots. Nonsteroidal anti-inflammatory drugs can be administered to reduce swelling. Another important component of treatment includes supporting the joint with bandages or boots. Horses with tendinitis should not be confined completely to the stall. They should be turned out in a small area, after inflammation is down, where they cannot generate a lot of speed or on a long line at a slow jog. (LLC, HorseDVM). This is key in the healing process so the tendon fibers do not heal bunched up as a scar, but in a parallel fashion which is normal and ideal for optimal athletic performance. Repeated ultrasounds should be taken to monitor tendon fiber repair. (Berkland, 2020).

Equine Aquacizer
Figure 2. Equine Aqua Therapy

An owner and/or trainer can prevent superficial digital flexor tendinitis with appropriate interval training and constant vigilance for any heat, swelling, off-stride, lameness, reluctance to switch leads, or any other physical abnormality that might point to this musculoskeletal issue. Owners, trainers, and support staff also have a responsibility to ensure that the racing facility and track surface is as technologically supportive as possible for musculoskeletal support. Injuries are often sustained because of insufficient track conditions including an irregular substrate, lack of base, moisture content, and grade. (Berkland, 2020; LLC, Horse DVM).

Works Cited

  1. Berkland, Jill, and Loretta A. Berkland. Kentucky Derby: Racehorse Physiology. Mar. 2020.
  2. Equine Aqua Therapy. Equine Therapy International, Equine Therapy International LLC.
  3. LLC, HorseDVM. Superficial Digital Flexor (SDF) Tendinitis: HorseDVM Diseases A-Z.
  4. Stephens, Stephanie. Equine Water Works. Equine Hydrotherapy in Horse Treadmills - HydroHorse, HydroHorse Inc. Equine Treadmill Systems.

By Jill Berkland, Kayla Walter, and Peggy Auwerda.
The report is a project for ANS313 Exercise Physiology of Animals