What you see. The starting point for addressing any equine health related issue is your observation.


Carpus (Knee) Swollen


Obvious swelling of the carpus (erroneously called "knee") of the front limb is common. There are multiple structures in this area that can become inflamed, thickened or fluid-filled.

The carpus is a common site for direct trauma, most commonly a kick from another horse. When this area sustains direct trauma, it tends to swell severely. There are several tendon sheaths which are located just under the skin here and they tend to swell when injured.

A moderate to severe swelling above or over the carpus, with modest or no lameness but difficulty advancing the limb can indicate inflammation of the extensor tendon sheaths. It is important for a vet to differentiate this from joint swelling itself. Swelling of a joint or tendon sheath often means that there is irritation or inflammation present that could worsen without proper treatment.

Swelling along with a wound to the area could indicate that the wound has caused infection of one of these important structures. Wounds to this area can involve these sheaths or the joint itself, and can be life-threatening.

Swelling here is often seen in older horses with chronic arthritis of the carpus. These horses usually have limited range of motion, and some have difficulty and pain associated with flexing the affected limb for the farrier.

Racehorses injure the carpus frequently and become lame with swelling of this area. In this case, there is usually a bone chip or other fracture of the small bones of the carpus. Fractures must be identified and treated promptly. Even tiny fractures involving joints quickly cause arthritis within the joint, which damages the joint permanently and reduces the likelihood for a good outcome.

  • Code Red

    Call Your Vet Immediately, Even Outside Business Hours
    • If severe lameness accompanies this sign.
    • If there is a wound present in the area.
    • If the results of the Whole Horse Exam (WHE) in the resting horse indicate fever (Temp >101F/38.3C) or heart rate greater than 48 BPM.
  • Code Orange

    Call Your Vet at Their First Available Office Hours
    • If there is modest or little lameness but significant swelling.
    • If the results of the Whole Horse Exam (WHE) suggest the horse is otherwise normal.
  • Code Yellow

    Contact Your Vet at Your Convenience for an Appointment
    • If the results of the Whole Horse Exam (WHE) suggest the horse is otherwise normal.
    • If the results of the Whole Horse Exam (WHE) suggest the horse is otherwise normal.

your role


What To Do

Assess the limb gently. Look for a wound. Test for range of motion and response to flexion. Press the swelling, looking for a pain response. Assess the horse for lameness at the walk and trot. Share your findings and concerns with your vet.

One of the most important considerations for you in assessing severity of the injury is whether it is accompanied by lameness, and the severity of the lameness. In many cases, horses with injury to this area will not be very lame but will have difficulty advancing the limb (bringing the limb forward).

What Not To Do

Do not assume that because the horse is not lame, that there is not a severe problem in the joint or nearby structures.

your vet's role

Your vet uses physical examination, lameness examination, and assessment of the carpus itself to determine generally what is going on. Often, diagnostics like radiography and ultrasound will be needed to form a complete picture and determine treatment plan and prognosis.
Questions Your Vet Might Ask:
  • When did you last notice that your horse was ok?
  • Is the horse limping or lame?
  • What does the horse do for a living?
  • Is there a wound near the carpus (knee)?
  • Is the horse out with others such that it might have been kicked?
  • When did you first notice the swelling?
  • Does the horse seem to have trouble advancing the limb?
  • What is the horse's age, sex, breed and history?
  • Does the horse show a pain response when you apply pressure to the area?
  • Does static flexion of the limb hurt?
  • Does the horse have a history of having been on the race track?
  • Does the horse react in pain when the limb is raised or manipulated?
  • What do you hope to do with your horse in the future?

Diagnoses Your Vet May Consider

The cause of the problem. These are conditions or ailments that are the cause of the observations you make.

Very Common
Less Common
more diagnoses

Author: Doug Thal DVM Dipl. ABVP