This document outlines the pathologic and pathophysiologic changes that occur in muscle injuries in horses. It begins with an introduction describing common causes of muscle injuries in horses. It then describes the pathologic changes, which include muscle fiber damage, inflammation, fibrosis, and muscle atrophy depending on the severity and duration of the injury. Next, it outlines key pathophysiologic changes such as calcium overload, oxidative stress, mitochondrial dysfunction, and apoptosis. These complex cellular and molecular changes can vary based on the injury severity and duration. In conclusion, understanding these pathologic and pathophysiologic muscle changes is important for properly diagnosing, treating, and preventing injuries in horses.

1. Pathologic and
pathophysiologic changes
of muscle in injury of horse
Prepared: Mohammad Asif Safi
Supervisor: associate professor Mohammad Moneer Tawfeeq

2. Outlines
• Introduction
• Pathologic changes
• Pathophysiologic changes
• Conclusion
• References

3. Introduction
 Muscle injuries are common in horses, and they can occur due
to various reasons such as!
 Overuse (overexertion)
 Trauma (Improper training)
 or genetic predisposition
 These injuries can range from mild strains to severe tears and can
result in significant pain, lameness, and decreased performance
 In general, muscle injuries result in inflammation, degeneration,
and regeneration of muscle fibers. (6),(7)

4. Introduction
 The inflammatory response is characterized by
infiltration of immune cells, such as neutrophils and
macrophages, into the injured area.
 Degeneration of muscle fibers occurs as a result of
direct trauma or ischemia (lack of blood flow) to the
affected area.
 Regeneration occurs when satellite cells (muscle stem
cells) are activated and differentiate into new muscle
fibers. (4)

5. 1- Pathologic Changes
 The pathologic changes that occur in muscle injuries
of horses depend on the severity and duration of the
injury.
 In mild injuries, there may be minimal damage to the
muscle fibers with only minor inflammation.
 In severe injuries, there may be extensive damage to
the muscle fibers with significant inflammation and
necrosis. (2)

6. 1- Pathologic Changes
 The following are some of the common pathologic
changes that occur in muscle injuries of horses:
1.Muscle Fiber Damage
2.Inflammation
3.Fibrosis
4.Muscle Atrophy (2),(6),(7)

7. Pathologic Changes
1. Muscle Fiber Damage:
 Muscle fiber damage is one of the primary pathologic changes
that occur in muscle injuries of horses.
 The extent of damage depends on the severity of the injury.
 In mild injuries, there may be only minor damage to the muscle
fibers with minimal disruption to their structure.
 In severe injuries, there may be extensive damage to the
muscle fibers with complete disruption of their structure. (2),(7)

8. Pathologic Changes
2. Inflammation
 Inflammation is a common response to muscle injury and is
characterized by an influx of inflammatory cells such as
neutrophils and macrophages into the injured area. (7)
3. Fibrosis
 Fibrosis is a process where fibrous tissue replaces damaged
muscle fibers.
 This process occurs when there is extensive damage to the
muscle fibers or when there is chronic inflammation. (6)

9. Pathologic Changes
4. Muscle Atrophy
 Muscle atrophy refers to a decrease in muscle mass due to
disuse or denervation.
 This process occurs when there is prolonged immobilization or
nerve injury. (2)

10. 2- Pathophysiologic Changes
 The pathophysiologic changes that occur in muscle injuries of
horses involve multiple cellular and molecular mechanisms.
 These changes are complex and can vary depending on the
severity and duration of the injury.
 The following are some of the common pathophysiologic
changes that occur in muscle injuries of horses. (5), (6)
1. Calcium Overload
2. Oxidative Stress
3. Mitochondrial Dysfunction
4. Apoptosis (5), (6)

11. 2- Pathophysiologic Changes
1. Calcium Overload
 Calcium overload is a common pathophysiologic change that
occurs in muscle injuries.
 This occurs when there is an influx of calcium ions into the
muscle fibers, which can lead to cell death and further tissue
damage. (5), (6)

12. 2- Pathophysiologic Changes
2. Oxidative Stress
 Oxidative stress occurs when there is an imbalance between
the production of reactive oxygen species (ROS) and the
body's ability to neutralize them.
 ROS can cause damage to cellular structures such as proteins,
lipids, and DNA.
 Oxidative stress is a common feature of muscle injuries and
can contribute to the development of chronic inflammation and
fibrosis. (5), (6)

13. 2- Pathophysiologic Changes
3. Mitochondrial Dysfunction
•Mitochondrial dysfunction refers to a decrease in
mitochondrial function due to injury or disease.
•Mitochondria are responsible for producing energy
within cells, and their dysfunction can lead to decreased
ATP production, increased ROS production, and cell
death .(5), (6)

14. 2- Pathophysiologic Changes
4. Apoptosis
o Apoptosis is a process where cells undergo programmed cell
death.
o This process occurs when there is extensive damage to the
muscle fibers or when there is chronic inflammation .(5), (6)

15. Conclusion
 The pathologic and pathophysiologic changes that occur in
muscles during an injury can have a significant impact on the
horse's performance and overall health.
 Understanding these changes is essential for proper diagnosis,
treatment, and prevention of muscle injuries in horses.

16. Refrences
1.Smith RKW. Tendon and ligament injury in sport horses. Vet Clin North Am Equine Pract
2008;24:45–vi.
2.Smith RKW, McIlwraith CW, Kadler KE, et al. Pathobiology of ligament injuries in horses. Vet Clin
North Am Equine Pract 1999;15(2):311–26
3.McIlwraith CW, Frisbie DD, Kawcak CE. Joint disease in the horse. St Louis: Elsevier Saunders;
2016.
4.Williams RBH, Harkins LSJ, Hammond CJL et al.. Muscle injuries in Thoroughbred racehorses:
clinical diagnosis and management. Vet Clin North Am Equine Pract 2008;24:191–208.
5.Williams RB, Harkins LS, Hammond CJ, et al. Pathophysiology of equine laminitis: A review. Vet J
2007;174(2):317–28.
6.Valberg SJ, Mickelson JR, Gallant EM et al.. Muscle disorders in horses. Vet Clin North Am
Equine Pract 2013;29:643–vii .
7.Stover SM, Pool RR. The equine athlete: injury, therapy and rehabilitation. Ames: Blackwell
Publishing; 2008.

17. Questions?