Lameness in the horse’s hock joint is one of the most common causes of altered hind end gait.

Hock lameness is characterized by shortened gait, weight shifting, stiffness when your horse picks their hind legs up, and reduced springiness off the ground when the horse picks up a canter or jumps.

Most performance horses will experience some form of hock lameness in their careers. Hock problems are most common in horses being asked to carry large amounts of weight on their hind ends, such as jumpers and upper-level dressage horses.

Vigilance and medical imaging of the hock are key to early detection and intervention. The good news is there are many effective treatment options for horses with hock lameness, keeping horses sound and pain-free after diagnosis.

Prevention of hock lameness starts with good management. Keep your horse at an appropriate body weight, support their joint health with a good nutritional program and watch for signs of soreness.

The Hock Joint

The hock is a group of joints that work to flex and extend the lower limb of the horse. The hock is considered a hinge joint because its movement is limited to flexion and extension in one plane (front to back). [1]

While the hock is usually thought of as a single joint, it is actually an area consisting of four separate joints that are each involved in moving the horse’s hind leg.

The four joints in the hock – consisting of one upper and three lower joints – include: [2]

  • Tibio-tarsal joint
  • Proximal inter-tarsal joint
  • Distal inter-tarsal joint
  • Tarso-metatarsal joint

The upper and largest joint is the tibio-tarsal joint. This joint is considered high-motion and responsible for most movement within the hock.

The lower joints are smaller and are considered low-movement but high shock absorbing. [3]

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Anatomy

These four joints include connections between the following ten bones:

  • Tibia
  • Talus
  • Calcaneus
  • Central tarsal bone
  • Fused 1st and 2nd tarsal bones
  • 3rd and 4th tarsal bone
  • 2nd, 3rd, and 4th metatarsal bone. [1]

The tibio-tarsal joint connects the horse’s tibia to its talus (a smaller bone within the hock). Unlike humans, this joint does not include the fibula, since the end of the horse’s fibula is incorporated into the end of the tibia. [2]

The proximal inter-tarsal joint is the junction between the talus and calcaneus and the central and 4th tarsal bones. The distal inter-tarsal joint articulates the numbered tarsal bones and the metatarsals. Finally, the tarso-metatarsal joint consists of the numbered tarsal bones and the metatarsals.

Ligaments

Three ligaments ensure the stability of the hock: [2]

  • Lateral collateral
  • Medial collateral
  • Long plantar ligament

Cartilage pads in the joint with synovial fluid in between allow for smooth movement throughout the range of motion.

The hock also has up to three bursae (fluid-filled pillows), allowing for smooth continuation of tendons down the horse’s lower leg. [2]

Function of the Hock

The joints within the hock perform two main functions:

  • Shock absorption
  • Propulsion [2]

Shock Absorption

The horse’s hock acts as a major shock absorber for the horse’s hind end. The anatomy of the hock allows the joint to be in a flexed position during the early portions of the stance phase (i.e. when the hoof makes contact with the ground).

This flexed position allows concussion to travel through the soft tissues and up the limb, reducing damaging concussive forces directly on the small structures of the lower limb. [3]

The hock also absorbs any torque created by breakover during the gait cycle. Breakover is the point of the gait cycle when the horse moves the heel off the ground onto the front of the hoof.

The breakover point is a location on the hoof where the most force is generated to propel the body forward. This point is similar to the ball of the foot on a human. [19]

For these reasons, the hock is very susceptible to damage and strain. [3] This shock absorption also allows for propulsion during push-off.

Propulsion

The major muscles that extend the hock are the biceps femoris and semitendinosus muscles. Extension of the hock allows for the horse’s body to be propelled forward. [1]

The major muscles responsible for flexing the hock are peroneus tertius (also known as the fibularis tertius), tensor fasciae latae, and extensor digitorum lateralis and longus. [2]

Flexion of the hock allows the limb to be lifted off the ground, propelled forward, and placed back on the ground without the toe dragging.

The hock is a unique joint in that it acts with the stifle during all movements. This is called a reciprocal apparatus; when the hock flexes, the stifle flexes, when the hock extends, the stifle extends and vice versa.

This reciprocal apparatus allows the horse to “sit” onto their hind end, which is crucial for hind end engagement during upper-level dressage and jumping. When this reciprocal apparatus is compromised, the horse can experience poor performance and hock pain. [4]

Signs and Symptoms of Hock Lameness

The symptoms of hock lameness that your horse may experience range from subtle to obvious. Most clinical signs are seen during performance and present as the horse feeling “off” when asked to push from the hind end.

Common signs of hock problems can include:

  • Shortened hind end gait
  • Reluctance to engage from the hind end
  • Reduced spring over jumps
  • Shifting weight when standing still
  • Resistance to going downhill
  • Stiffness that resolves during warm-up
  • Heat and swelling in the hock area
  • Stiffness and reactivity when asked to pick up the hind legs
  • Soreness in the back or stifle from movement compensation [5]

Causes of Hock Lameness

Hock lameness is usually a result of repeated concussion and shock absorption during activities such as jumping, collected work, and travelling down steep hills.

Horses with conformational flaws of the hind limbs are more likely to develop hock issues. Horses born with sickle hocks, straight hocks, or cow hocks are more prone to arthritis and injury due to the altered function of the joints. [2] No one breed is more prone to hock lameness.

Hock lameness can also be caused by arthritis, injury, inflammation, developmental issues or bone problems.

Arthritis or Bone Spavin:

Osteoarthritis (also known as degenerative joint disease) involves progressive deterioration of the cartilage, bone and other components of the joint due to wear and tear.

Bone spavin is a term used to describe degenerative arthritis of the smaller hock joints. It is seen in older horses and commonly causes hindlimb lameness.

The hock is especially prone to arthritis, specifically in the three lower joints because of their role in shock-absorption.

Arthritis is characterized by changes in the cartilage and bone that can inhibit normal motion and increase inflammation. This is an extremely common issue in senior horses that can contribute to poor performance and result in early retirement. [6]

Osteochondritis Dissecans (OCD):

OCD is a developmental disease that can present as small bony fragments or chips breaking off within the hock joints. [6]

Horses with OCD have abnormal cartilage, resulting in the separation of the bone and cartilage from articular surfaces (joints). OCD can also result from excessive training causing lesions in the cartilage and bone.

Septic Arthritis:

Septic arthritis is inflammation of the hock joint caused by bacterial growth within the joint capsule. This serious and potentially life-threatening condition presents as severe lameness and heat in the joint.

Septic arthritis can be caused by bacterial introduction after injury, surgery, joint injection, or systemic infection in the bloodstream. [7]

Capped hocks:

A capped hock presents as warm swelling at the point of the hock. The bursae situated at the point of the hock usually provide a smooth surface for the digital flexor tendons to travel over.

When the bursae become inflamed (usually after trauma), the tendons do not have a smooth surface underneath them. Capped hocks can be asymptomatic or your horse may experience pain with every step.

This condition is caused by repeated concussive forces travelling up the limb, such as from a horse kicking a solid wall. If capped hocks are apparent, your veterinarian will investigate to rule out an underlying fracture. [8]

Fracture:

Like any bone in the horse’s body, the bones of the hock are susceptible to fracture from external trauma or repeated extreme concussion.

Hock fractures can involve fractures of any of the bones in the hock and present as extreme lameness with heat and tenderness on palpation. [9]

Ligament injury:

Because the ligaments of the hock are short and thick, ligament injury is relatively rare. However, ligament injury does occur and can present as lameness and heat in the hock area. [9]

Subchondral Bone Cysts:

Cysts within the hock joint may appear if osteoarthritis goes untreated. These fluid-filled pockets within the joint will cause pain and inflammation. [6]

Diagnosing Hock Lameness

To diagnose hock lameness in your horse, your veterinarian will first palpate the hock for any swelling or heat.

They will then perform a lameness exam, watching the horse walk, trot, and canter in a straight line and circle. They may perform a flexion test to simulate stress to the joint. [17]

The vet may also perform x-rays, taking multiple views of the joint to visualize any bony changes. To check for soft-tissue injury, the vet can perform an ultrasound.

If hock lameness is apparent, but neither x-rays nor ultrasound reveals any diagnosis, the vet may refer the horse for additional imaging such as CT or MRI.

Treatment

Treatment of hock lameness is largely dependent on diagnosis. Horses with mild hock pain coupled with non-remarkable x-ray images may benefit from using non-steroidal anti-inflammatory drugs (NSAIDS) or from reduced workload.

More severe cases of lameness may require further intervention.

With prompt intervention, horses that experience hock lameness have a good chance of recovery. Although many causes of hock lameness cannot be cured, they can be managed and prevented.

Joint Injections

Joint injections can help to reduce inflammation and increase lubrication in the joint capsule. Depending on the severity of arthritis or inflammation, your veterinarian may choose to inject different medications including:

Hyaluronic acid and corticosteroids: These compounds have anti-inflammatory effects, reducing pain in the joint. [10]

Interleukin-1 Receptor Antagonist Protein (IRAP): a protein naturally produced by the horse’s body that has been shown to reduce inflammation and promote cartilage regeneration. [11]

Platelet Rich Plasma (PRP): A component of the horse’s blood that can stimulate and repair damaged cartilage when injected into the joint space. [12]

Autologous Protein Solution (Pro-stride): A derivative of the horse’s blood that can reduce inflammation, stimulate tissue repair, and reduce pain. [13]

Arthroscopy

Arthroscopic surgery is a minimally invasive procedure used to examine and treat the joints. It involves passing an arthroscope through a small incision on the leg.

Arthroscopy can be performed to remove any bone chips or cartilage fragments that occur within the joint. This procedure can also be performed when fractures of the joint need to be fixated in place. [14]

Antibiotic Treatment

Because septic arthritis occurs due to bacterial infection, antibiotics are necessary for treatment. Vets may give oral antibiotics and flush the infected joint with an antibiotic solution. [15]

Cyst Aspiration

If your horse has been diagnosed with severe subchondral bone cysts, your veterinarian may elect to aspirate the cyst contents with a fine needle. This will remove the source of pain in your horse’s joint and resolve the lameness. [16]

Laser Fusion

In horses with chronic hock pain, a procedure known as laser arthrodesis may be conducted to surgically fuse together the bones of the hock. This usually resolves the pain and returns the horse to soundness. [20]

How to Prevent Hock Problems

Many of the common causes of hock lameness can be prevented with exercise management, good feeding practices, supplementation and maintaining your horse at a healthy body condition.

Hock lameness can directly result from overwork. Maintaining a suitable exercise program can help to support hock integrity and avoid injury.

Training regimes should be balanced between jumping or collection work, conditioning on the flat, and hill work. When starting a new training regimen, always begin gradually and avoid over-fatiguing the horse.

Avoid work on very hard surfaces, which put greater concussive forces on the hock joint and can increase the risk of osteoarthritis. Instead, work your horse on softer surfaces that allow the hoof to sink slightly, reducing the shock absorption required by the hock.[6]

Overweight horses or easy keepers are more likely to develop hock arthritis, especially as they age. Keeping your horse at an appropriate weight will reduce the risk of arthritis. [18]

Provide regular farrier care to your horse to maintain healthy hooves. The hoof plays an important role in shock absorption and a well-trimmed hoof will limit the transfer of impact to the joints.

Finally, when purchasing a new horse make sure to choose a horse that is appropriate for your intended use. Conformation issues can lead to a higher risk of hock problems. Ask your veterinarian to examine the horse’s joints during the pre-purchase exam and make sure they know which discipline you intend to use the horse for.

Supporting Joints Through Diet

Your horse’s feeding program directly contributes to joint health by supplying the nutrients required to maintain healthy bones, cartilage and synovial fluid.

In particular, amino acids and the minerals copper and zinc are required to form collagen proteins found in cartilage tissue.

Calcium and phosphorous are the two most important minerals found in bone and they must be supplied in the correct ratio to support optimal growth and bone strength.

It is also important not to over-supply energy in the diet. Foals fed a diet with 129% of their daily calorie requirement were more likely to develop dyschondroplasia or abnormal cartilage growth. [21]

Work with a qualified equine nutritionist to design a balanced feeding program that provides adequate levels of protein, vitamins and minerals without over-supplying energy. You can submit your horse’s information online for a free diet balancing.

Nutritional supplements such as methyl-sulfonate-methane (MSM), hyaluronic acid, and omega-3 fatty acids can also support joint health and reduce inflammation.

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To learn about more joint supplements that work (and which ones don’t work), read our guide to the top join supplements that are backed by peer-reviewed research.

Looking for more ways to support your horse’s joint health and reduce the risk of hock lameness? Check out our article on the 8 Key Principles for Supporting Joint Health in Horses.

Is Your Horse's Diet Missing Anything?

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References

  1. Dyson, S. and Murray, R. The tarsus. Equine MRI. 2010.
  2. Budras, K. and Sack, W. Anatomy of the Horse: 6th Edition. Schlütersche. 2012.
  3. Dyson, S. and Ross, M. The tarsus. Veterian Key. 2016.
  4. Molenaar, B. Kinematics of the Reciprocal Apparatus in the Horse . Anatomia Histologia Ambryologia. 1983. View Summary
  5. Lewis, R. Lameness in the Rodeo Horse . AAEP. 2001.
  6. Taylor, S. Some Studies On Equine Hock Joint Disease With Particular Reference To Tarsal Osteoarthritis. University of Glasgow. 1977.
  7. Brokken, M. et al. Joint Disorders in Horses. Merck Manual. 2020.
  8. Van Pelt, R. and Riley, W. Traumatic subcutaneous calcaneal bursitis (capped hock) in the horse. Journal of the Am Vet Med Assoc. 1968. View Summary
  9. Nixon, A . Fractures and Luxations of the Hock. Equine Fracture Repair. 2019.
  10. Auer, J. et al. Effect of hyaluronic acid in naturally occurring and experimentally induced osteoarthritis. Am Journal of Vet Research. 1980. View Summary
  11. Machado, T. and Massoco, C. Effects of blood-derived products and sodium hyaluronate on equine synovial fluid cells and on synovial fluid from osteochondrotic joints of horses after arthroscopy and administration of treatment. Am Journal of Vet Research. 2019.View Summary
  12. Textor,J. et al. Synovial fluid growth factor and cytokine concentrations after intra-articular injection of a platelet-rich product in horses. The Vet Journal. 2013.View Summary
  13. King, W. et al. The Use of Autologous Protein Solution (Pro-Stride®) and Leukocyte-Rich Platelet-Rich Plasma (Restigen®) in Canine Medicine. Vet Med. 2021.
  14. Clegg, P. Differential diagnosis of a swollen hock in the horse. In Practice. 2003.
  15. Morton, A. Diagnosis and Treatment of Septic Arthritis. Vet Clinics: Equine Prac. 2005.
  16. McIlwraith, C. Subchondral bone cysts in the horse: aetiology, diagnosis and treatment options. Equine Vet Edu. 2010.
  17. Ross, M. Dyson, S. Diagnosis and Management of Lameness in the Horse: Second Edition. Elsevier. 2011.
  18. Duberstein, K. and Johnson, E. Caring for the older horse: Common problems and solutions. University of Georgia. 2018.
  19. Page, B. and Hagen, T. Breakover of the hoof and its effect on stuctures and forces within the foot. Journal of Equine Vet Science. 2002.
  20. Zubrod, C. et al. Comparison of three methods for arthrodesis of the distal intertarsal and tarsometatarsal joints in horses. Vet Surg. 2005. View Summary
  21. National Research Council. Nutrient Requirements of Horses: 6th Revised Edition. 2007.