Joint Disease
Lameness is a frequent problem and one that is often frustrating for owners when their horse is unable to be used for the intended purpose. Clinical signs vary tremendously from a horse that just doesn't look or feel right to an obvious gait abnormality that you can see.
All of the different types of joint disease have one common denominator - they cause inflammation within the joint.
Inflammation causes pain and in the horse this is manifested as lameness. Over time, the inflammation causes irreversible deterioration to the cartilage in the joint, so it is important to detect abnormalities early and start treatment promptly.
Unlike bone, cartilage has a very poor healing ability and once damage occurs it is never again replaced by normal cartilage.
Damaged cartilage is significantly inferior in strength and biomechanical properties. Areas where there is thinning of cartilage or total absence lead to the ends of bones
How joint inflammation happens
- Injury to a soft tissue structure which either supports and stabilises the joint (e.g. collateral ligament) or is within the joint (e.g. cruciate ligament). This results in instability of the joint.
- Normal everyday athletic activity or overuse resulting in slowly progressive 'wear and tear' of the joint.
- Bone chips or fragments of bone and cartilage (termed 'osteochondral fragments' inside a joint)
- Fracture involving the surface of the joint
- Previous joint infection due to either a puncture or penetrating wound
- Poor conformation leading to excessive pressure on one side of the joint
- Congenital abnormalities such as angular limb deformities in foals
- Osteochondrosis (OCD) and subchondral bone cysts
Diagnosis
A veterinary examination is required in order to perform a detailed lameness evaluation and isolate the lameness to a particular joint.
There are different severities of lameness, and the horse may show a head bob, a shortened stride length, reduced joint flexion or just simply be performing poorly.
When there is inflammation within a joint the following changes occur:
- Joint distension - there is an increase of joint fluid within the joint which can be palpated and/ or visually observed. This results in increased pressure inside the joint and is also a cause of pain.
- Reduced joint mobility - overtime the joint capsule inflammation leads to thickening and fibrosis which means there is reduced joint flexion.
- Pain on flexion
After an examination, the veterinarian will use diagnostic imaging such as radiographs which are commonly taken to assess the joint and make a specific diagnosis.
Although it can occur in any joint in the body, the most common joints affected are the fetlocks, knees, hocks and stifles. Horses that perform in certain disciplines are predisposed to typical joint conditions due to the work that they do.
MEDICAL TREATMENT
Oral Joint supplements
A vast number of different oral joint supplements are available for the horse. The specific formulation, concentration and source of products differs considerably, however most contain one or more of the following; chondroitin sulfate, glucosamine, hyaluronan, MSM. Many of these products work by providing molecules which are naturally found and have important properties in cartilage or joint fluid and which undergo depletion when there is inflammation within a joint. Scientific studies have indicated that these products are effective in the treatment of joint disease in humans. However in horses, treatment efficacy is based more on individual opinion rather than substantiated by quality scientific studies.
An interesting report in human literature compared the label ingredient with the independent testing of the products and found little correlation to the label claim and content or price and content. This potentially emphasizes the use of trusted brands that have at least undergone some testing.
Nonsteroidal anti-inflammatory medications
Phenylbutazone ('bute') has been the mainstay of treatment for joint disease for many decades and works well to decrease lameness due to its rapid onset of action and strong anti-inflammatory action. Bute however is not a long term treatment for horses involved in competition, due to its long swabbing time and both kidney and intestinal side effects.
Meloxican is a newer anti-inflammatory medication which is reported to have fewer side effects than phenylbutazone and a shorter withdrawal time.
Hyaluronic acid (HA) is an essential and normal component of joint fluid and cartilage. It provides joint fluid with the properties of lubrication and elasticity, which is necessary for a smooth and even gliding joint surface. HA is commonly injected in conjunction with a corticosteroid inside a joint and also acts as a natural anti-inflammatory and enhances the action of the steroid. HA can also be injected intra-venously in conjunction with Pentosan (see below).
Pentosan and Pentosan Halo. Pentosan polysulphate is derived from a plant (beechwood extract) and is registered for intramuscular administration in the horse. Pentosan Halo contains an additional ingredient, HA, which is administererd in a separate syringe and given intra-venously in the horse. These products aid in healing of mild cartilage disease. Experimental studies performed in horses have revealed improvement in lameness and joint flexion as well as reduced inflammation inside an arthritic joint.
Corticosteroids are the most potent anti- inflammatories available and are injected directly into a joint (termed 'intra-articular') to provide rapid pain relief. Furthermore
it has been shown in controlled scientific studies that using 'low doses' of corticosteroids can improve the integrity of the cartilage.
Controversy exists surrounding the use of intra-articular corticosteroids due to the reported potential side effects. Much of this controversy is based on unsubstantiated statements in the lay press. Furthermore studies which revealed potentially harmful effects of IA steroids were conducted using normal joints and cartilage. Current research suggests that inflamed and arthritic joints do not exhibit the same harmful effects seen in normal joints when IA steroids are administered.
Some consideration should be given to the reported incidence of corticosteroid induced laminitis; however no direct association has ever been proved. Caution should be undertaken in horses which have had laminitis and which are prone to developing laminitis.
IRAP (Interleukin 1 receptor antagonist protein)
Blood is taken from the horse and incubated with special glass beads that promote the production of regenerative and anti-inflammatory proteins by the white cells in the blood. The sample is centrifuged and the serum containing these proteins is harvested. This serum is injected into the affected joint. Usually a series of three to four injections is performed every 1-2 weeks.
This treatment can work well for horses with mild arthritis and no significant radiographic changes. IRAP is not swabbable as it is made from the body's own proteins.
Training Changes
In horses with initiating mild arthritis, all that may be required to keep the animal sound, is increasing the warm-up period prior to intense work.
In other cases it is necessary to reduce the work intensity and duration whilst treatments are initiated to allow medication time to take effect.
Complementary therapies such as massage, acupuncture and chiropractic can also be incorporated into the training regime. The response to these adjunctive treatments is quite variable from horse to horse and therefore some experimentation to find out what works may be necessary.
SURGICAL TREATMENT
Surgical treatment to remove either the offending OR major contributing cause of arthritis is required in the following cases:
- Bone chips - these can occur as a consequence of the arthritis or intensive training
- OCD (osteochondrosis) - it is a congenital problem where due to a variety of reasons, such as nutritional and genetic disposition, bone chips form in specific locations.
- Bone cysts - these are areas where there is a lack of bone below an area of (usually abnormal) cartilage
- Medicating a joint and making it pain- free in the cases listed above will only aggravate the arthritis and further its progression. For this reason X-rays are commonly performed to assess the affected joint in order to screen for potential surgical problems.
Arthroscopy
Arthroscopy is the most common method by which joints are assessed and surgically treated. It involves making keyhole incisions directly into the joint and placing a special instrument called an arthroscope into the joint, so that the interior can be viewed on a monitor. This technique has been adapted from humans and reduces post-operative complications such as infection and scar tissue restriction as used to be common after open joint surgeries.
Joint resurfacing techniques
Due to the inherent poor healing of cartilage defects, a considerable amount of research has been performed in the last decade evaluating different surgical treatments for focal cartilage defects.
Despite this, problems exist with each technique currently developed.
For example there can be great difficulty in gaining surgical access to certain areas of the joint where joint disease occurs (e.g. weight bearing surfaces of the stifle joint).
Often, specialised equipment is required as well as specialised surgical expertise and this comes with a substantial cost.
This is why many of the techniques scientifically evaluated have not been found to be easily applicable in the clinical setting. Furthermore, true, evidence-based follow-up of horses with naturally occurring clinical joint disease, and the outcome following treatment is lacking, making the justification of using any of these techniques very difficult.
Arthrodesis
Assisted fusion of a joint is sometimes indicated when destruction to the joint is beyond any other treatment. Arthrodesis can be carried out using metallic hardware (surgical plates and/ or screws) or achieved through chemical (MIA, medical grade alcohol) or laser-based methods.
In low motion joints such as the pastern and distal hock joints, athletic activity carries a reasonable prognosis for athletic soundness. This is in direct contrast to arthrodesis in high motion joints such as the knee and fetlock where the aim of the fusion is to alleviate the pain associated with movement of the joint and to salvage the horse for non-athletic purposes.
Stem cells
An exciting emerging application for stem cell therapy in horses is in the management of lameness associated with osteoarthritis.
Stem cells are harvested from the bone marrow or fat and are injected directly into the affected joint. Stem cell treatment has been used in conjunction with arthroscopic surgery when typically the results from surgery alone would be poor.
The potential benefits for the use of stem cells in osteoarthritic joints relates to the anti-inflammatory properties of stem cells and also their ability to embed within
the joint as well as their capacity for self renewal resulting in a prolonged duration of effect. Candidates for stem cell treatment for osteoarthritis are those horses that
fail to respond or become refractory to conventional treatments or those horses that suffer side effects from non-steroidal anti-inflammatory or corticosteroid medication.
Conclusion
The choice of treatment for joint disease must be based on accurate understanding of the joint(s) involved, knowledge of underlying factors contributing to the joint disease, together with the current severity of damage and clinical signs. Once this information is known an informed treatment plan can be outlined and recommended.
Often it is a case of trying the simplest form of management and medical intervention. If the disease progresses or the animal fails to respond to the current medication an additional treatment is added to the treatment regime which is stronger and superior to the first. This way the 'minimal' mode of intervention is sought. This is depicted in the treatment pyramid image above.
Joint Disease
Lameness is a frequent problem and one that is often frustrating for owners when their horse is unable to be used for the intended purpose. Clinical signs vary tremendously from a horse that just doesn't look or feel right to an obvious gait abnormality that you can see.
All of the different types of joint disease have one common denominator - they cause inflammation within the joint.
Inflammation causes pain and in the horse this is manifested as lameness. Over time, the inflammation causes irreversible deterioration to the cartilage in the joint, so it is important to detect abnormalities early and start treatment promptly.
Unlike bone, cartilage has a very poor healing ability and once damage occurs it is never again replaced by normal cartilage.
Damaged cartilage is significantly inferior in strength and biomechanical properties. Areas where there is thinning of cartilage or total absence lead to the ends of bones
How joint inflammation happens
- Injury to a soft tissue structure which either supports and stabilises the joint (e.g. collateral ligament) or is within the joint (e.g. cruciate ligament). This results in instability of the joint.
- Normal everyday athletic activity or overuse resulting in slowly progressive 'wear and tear' of the joint.
- Bone chips or fragments of bone and cartilage (termed 'osteochondral fragments' inside a joint)
- Fracture involving the surface of the joint
- Previous joint infection due to either a puncture or penetrating wound
- Poor conformation leading to excessive pressure on one side of the joint
- Congenital abnormalities such as angular limb deformities in foals
- Osteochondrosis (OCD) and subchondral bone cysts
Diagnosis
A veterinary examination is required in order to perform a detailed lameness evaluation and isolate the lameness to a particular joint.
There are different severities of lameness, and the horse may show a head bob, a shortened stride length, reduced joint flexion or just simply be performing poorly.
When there is inflammation within a joint the following changes occur:
- Joint distension - there is an increase of joint fluid within the joint which can be palpated and/ or visually observed. This results in increased pressure inside the joint and is also a cause of pain.
- Reduced joint mobility - overtime the joint capsule inflammation leads to thickening and fibrosis which means there is reduced joint flexion.
- Pain on flexion
After an examination, the veterinarian will use diagnostic imaging such as radiographs which are commonly taken to assess the joint and make a specific diagnosis.
Although it can occur in any joint in the body, the most common joints affected are the fetlocks, knees, hocks and stifles. Horses that perform in certain disciplines are predisposed to typical joint conditions due to the work that they do.
MEDICAL TREATMENT
Oral Joint supplements
A vast number of different oral joint supplements are available for the horse. The specific formulation, concentration and source of products differs considerably, however most contain one or more of the following; chondroitin sulfate, glucosamine, hyaluronan, MSM. Many of these products work by providing molecules which are naturally found and have important properties in cartilage or joint fluid and which undergo depletion when there is inflammation within a joint. Scientific studies have indicated that these products are effective in the treatment of joint disease in humans. However in horses, treatment efficacy is based more on individual opinion rather than substantiated by quality scientific studies.
An interesting report in human literature compared the label ingredient with the independent testing of the products and found little correlation to the label claim and content or price and content. This potentially emphasizes the use of trusted brands that have at least undergone some testing.
Nonsteroidal anti-inflammatory medications
Phenylbutazone ('bute') has been the mainstay of treatment for joint disease for many decades and works well to decrease lameness due to its rapid onset of action and strong anti-inflammatory action. Bute however is not a long term treatment for horses involved in competition, due to its long swabbing time and both kidney and intestinal side effects.
Meloxican is a newer anti-inflammatory medication which is reported to have fewer side effects than phenylbutazone and a shorter withdrawal time.
Hyaluronic acid (HA) is an essential and normal component of joint fluid and cartilage. It provides joint fluid with the properties of lubrication and elasticity, which is necessary for a smooth and even gliding joint surface. HA is commonly injected in conjunction with a corticosteroid inside a joint and also acts as a natural anti-inflammatory and enhances the action of the steroid. HA can also be injected intra-venously in conjunction with Pentosan (see below).
Pentosan and Pentosan Halo. Pentosan polysulphate is derived from a plant (beechwood extract) and is registered for intramuscular administration in the horse. Pentosan Halo contains an additional ingredient, HA, which is administererd in a separate syringe and given intra-venously in the horse. These products aid in healing of mild cartilage disease. Experimental studies performed in horses have revealed improvement in lameness and joint flexion as well as reduced inflammation inside an arthritic joint.
Corticosteroids are the most potent anti- inflammatories available and are injected directly into a joint (termed 'intra-articular') to provide rapid pain relief. Furthermore
it has been shown in controlled scientific studies that using 'low doses' of corticosteroids can improve the integrity of the cartilage.
Controversy exists surrounding the use of intra-articular corticosteroids due to the reported potential side effects. Much of this controversy is based on unsubstantiated statements in the lay press. Furthermore studies which revealed potentially harmful effects of IA steroids were conducted using normal joints and cartilage. Current research suggests that inflamed and arthritic joints do not exhibit the same harmful effects seen in normal joints when IA steroids are administered.
Some consideration should be given to the reported incidence of corticosteroid induced laminitis; however no direct association has ever been proved. Caution should be undertaken in horses which have had laminitis and which are prone to developing laminitis.
IRAP (Interleukin 1 receptor antagonist protein)
Blood is taken from the horse and incubated with special glass beads that promote the production of regenerative and anti-inflammatory proteins by the white cells in the blood. The sample is centrifuged and the serum containing these proteins is harvested. This serum is injected into the affected joint. Usually a series of three to four injections is performed every 1-2 weeks.
This treatment can work well for horses with mild arthritis and no significant radiographic changes. IRAP is not swabbable as it is made from the body's own proteins.
Training Changes
In horses with initiating mild arthritis, all that may be required to keep the animal sound, is increasing the warm-up period prior to intense work.
In other cases it is necessary to reduce the work intensity and duration whilst treatments are initiated to allow medication time to take effect.
Complementary therapies such as massage, acupuncture and chiropractic can also be incorporated into the training regime. The response to these adjunctive treatments is quite variable from horse to horse and therefore some experimentation to find out what works may be necessary.
SURGICAL TREATMENT
Surgical treatment to remove either the offending OR major contributing cause of arthritis is required in the following cases:
- Bone chips - these can occur as a consequence of the arthritis or intensive training
- OCD (osteochondrosis) - it is a congenital problem where due to a variety of reasons, such as nutritional and genetic disposition, bone chips form in specific locations.
- Bone cysts - these are areas where there is a lack of bone below an area of (usually abnormal) cartilage
- Medicating a joint and making it pain- free in the cases listed above will only aggravate the arthritis and further its progression. For this reason X-rays are commonly performed to assess the affected joint in order to screen for potential surgical problems.
Arthroscopy
Arthroscopy is the most common method by which joints are assessed and surgically treated. It involves making keyhole incisions directly into the joint and placing a special instrument called an arthroscope into the joint, so that the interior can be viewed on a monitor. This technique has been adapted from humans and reduces post-operative complications such as infection and scar tissue restriction as used to be common after open joint surgeries.
Joint resurfacing techniques
Due to the inherent poor healing of cartilage defects, a considerable amount of research has been performed in the last decade evaluating different surgical treatments for focal cartilage defects.
Despite this, problems exist with each technique currently developed.
For example there can be great difficulty in gaining surgical access to certain areas of the joint where joint disease occurs (e.g. weight bearing surfaces of the stifle joint).
Often, specialised equipment is required as well as specialised surgical expertise and this comes with a substantial cost.
This is why many of the techniques scientifically evaluated have not been found to be easily applicable in the clinical setting. Furthermore, true, evidence-based follow-up of horses with naturally occurring clinical joint disease, and the outcome following treatment is lacking, making the justification of using any of these techniques very difficult.
Arthrodesis
Assisted fusion of a joint is sometimes indicated when destruction to the joint is beyond any other treatment. Arthrodesis can be carried out using metallic hardware (surgical plates and/ or screws) or achieved through chemical (MIA, medical grade alcohol) or laser-based methods.
In low motion joints such as the pastern and distal hock joints, athletic activity carries a reasonable prognosis for athletic soundness. This is in direct contrast to arthrodesis in high motion joints such as the knee and fetlock where the aim of the fusion is to alleviate the pain associated with movement of the joint and to salvage the horse for non-athletic purposes.
Stem cells
An exciting emerging application for stem cell therapy in horses is in the management of lameness associated with osteoarthritis.
Stem cells are harvested from the bone marrow or fat and are injected directly into the affected joint. Stem cell treatment has been used in conjunction with arthroscopic surgery when typically the results from surgery alone would be poor.
The potential benefits for the use of stem cells in osteoarthritic joints relates to the anti-inflammatory properties of stem cells and also their ability to embed within
the joint as well as their capacity for self renewal resulting in a prolonged duration of effect. Candidates for stem cell treatment for osteoarthritis are those horses that
fail to respond or become refractory to conventional treatments or those horses that suffer side effects from non-steroidal anti-inflammatory or corticosteroid medication.
Conclusion
The choice of treatment for joint disease must be based on accurate understanding of the joint(s) involved, knowledge of underlying factors contributing to the joint disease, together with the current severity of damage and clinical signs. Once this information is known an informed treatment plan can be outlined and recommended.
Often it is a case of trying the simplest form of management and medical intervention. If the disease progresses or the animal fails to respond to the current medication an additional treatment is added to the treatment regime which is stronger and superior to the first. This way the 'minimal' mode of intervention is sought. This is depicted in the treatment pyramid image above.