Understanding stifle injuries in the horse
The equine athlete is a powerful animal, capable of helping us to work as a team to enjoy so many diverse disciplines. Lameness and injury can be challenging, frustrating and disappointing when we know our equine companion is hurt. Through this medium, we want to help educate horse enthusiasts on a variety of equine sports medicine topics.
PART 1 — Stifle Anatomy
From the anatomy perspective, I think the stifle joint is one of the most cool and intricate joints in the horse. I think you will agree after learning more.
Starting at the basics, the stifle is located in the hindlimb of the horse. It is the anatomical equivalent to our human knee joint. As such, it is the connection between the femur, tibia and patella (knee cap) bones. Unlike dogs or humans, horses have no developed fibula.
The stifle joint itself can be broken down into three separate compartments.
- Femoropatellar (front compartment)
- Medial femorotibial (inside compartment)
- Lateral femorotibial (outside compartment)
Each of these three joint compartments can be afflicted with disease/injury (Part 2, 3, 4). Although these compartments can be thought of as “separate” barriers, communication of molecules, drugs or proteins can sometimes transfer between the three compartments. Specifically, there is a high degree of communication between the medial femorotibial and femoropatellar. However, the lateral femorotibial is almost always isolated by itself.
Like all joints, the cartilage surfaces are extremely important for the gliding function during clean movement. The distal (bottom) femur has some unique shapes to it. On the front, there are two trochlear ridges (medial/inside & lateral/outside) and on the back/bottom, two condyles (again, medial & lateral — I think your catching on!).
One of the most fascinating things about the stifle compared to other equine joints is the amount of soft tissue present stabilizing all the structures. On the top of the tibia, sandwiched between the femoral condyles and the tibial plateau is the famous meniscus. Think of the meniscus as a soft tissue shock absorber that cushions the tibia from the large forces transmitted through the hindlimb with propulsion.
Beyond the meniscus, there are fourteen (14!) ligaments that stabilize the meniscus, femur, tibia and patella. This is significantly more than any other joint. No wonder soft tissue injury in the stifle is common! Ligaments include:
- Patellar (3)
- Collateral (2)
- Meniscotibial (4)
- Meniscofemoral (1)
- Femoropatellar (2)
- Cruciates (2)
Lastly, we can’t forget about all that muscle. Many of the important tendons we worry about lower in the hindlimb start up near the the pelvis, femur or proximal (top part of) tibia. There are too many to name, but the major groups that contribute to the stifle include the quadriceps and gluteals.
That is a basic run down of what all is involved in the stifle. Now with this knowledge to move on to types of stifle injury in Part 2…
Questions, comments, concerns. Anything your still curious about. Email us! highline.equine@gmail.com
Regards,
your Highline Equine Veterinary Sports Medicine and Primary Care team
