Curb has been historically defined as enlargement or thickening of the long plantar ligament along the back side (plantar aspect) of the equine hindlimb. Visible swelling evident just below the point of the hock was thought to be a result of inflammation and secondary fibrosis (scarring) of the long plantar ligament.
Recent advances in diagnostic ultrasonography, however, have helped equine veterinarians redefine curb as a collection of multiple soft tissue injuries within the distal plantar hock region and not solely associated with the long plantar ligament.
CAUSES OF CURB
In addition to swelling associated with the long plantar ligament, injury to the following structures can also contribute to the appearance of curb:
Peritendonous/periligamentous tissues along the plantar hock region. Fluid accumulation and/or fibrosis (firm swelling) associated with the peritendonous/ periligamentous tissues are almost always found in conjunction with curb, often in the absence of other underlying injuries.
Superficial digital flexor tendon (SDFT). Recent evidence suggests that injury to the superficial digital flexor tendon as a cause of curb is as common as injury to the long plantar ligament.
Deep digital flexor tendon (DDFT). Injury to the deep digital flexor tendon as a cause of curb is less common than SDFT injury.
Tarsocrural lateral collateral ligament (LCL). Collateral ligament desmitis in the tarsocrural joint is a relatively uncommon cause of curb.
Tendon of the gastrocnemius muscle. Injury to the tendon of the gastrocnemius muscle as a cause of curb is usually seen in combination with injury to the long plantar ligament and rarely by itself.
Curb is most common in Standardbreds, in which poor (sickle-hocked) conformation is implicated as the predisposing factor.
Curb is readily visible as swelling along the distolateral hock region of the horse.
Local perineural anesthesia (i.e. nerve blocking) can be helpful but is usually not necessary nor specific with respect to cause(s).
Ultrasonography has proved to be invaluable with regard to identifying specific structures involved, and therefore is implemented in most diagnostic strategies. Accurately determining the affected structures allows veterinarians to formulate an effective treatment plan.
Curb is treated similarly to chronic desmitis (ligament inflammation). In our hands, a combination of stall rest, topical therapy and extracorporeal shock wave therapy (ESWT) has proven to be very effective at hastening resolution of curb.
To learn more about these treatment strategies, click HERE.