# Stifle joint

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{{Short description|Quadruped}}
{{More citations needed|date=February 2024}}
thumb|This dog's stifle joint is labeled 12
The '''stifle joint''' (often simply '''stifle''') is a complex [joint](/source/joint) in the [hind limb](/source/hind_limb)s of [quadruped](/source/quadruped) [mammal](/source/mammal)s such as the [sheep](/source/sheep), [horse](/source/horse) or [dog](/source/dog). It is the equivalent of the human [knee](/source/knee) and is often the largest [synovial joint](/source/synovial_joint) in the animal's body. The stifle joint joins three bones: the [femur](/source/femur), [patella](/source/patella), and [tibia](/source/tibia). The joint consists of three smaller ones: the [femoropatellar](/source/Knee) joint, medial {{linktext|femorotibial}} joint, and lateral femorotibial joint.<ref>{{Cite journal |last=Carpenter |first=D. H. |last2=Cooper |first2=R. C. |date=7 July 2008|title=Mini Review of Canine Stifle Joint Anatomy |url=https://onlinelibrary.wiley.com/doi/10.1046/j.1439-0264.2000.00289.x |journal=Anatomia, Histologia, Embryologia |language=en |volume=29 |issue=6 |pages=321–329 |doi=10.1046/j.1439-0264.2000.00289.x |issn=0340-2096|url-access=subscription }}</ref>

The stifle joint consists of the femorotibial articulation ([femoral](/source/femoral_condyle) and [tibial](/source/Medial_condyle_of_tibia) [condyles](/source/condyles)), femoropatellar articulation (femoral [trochlea](/source/trochlea_of_humerus) and the [patella](/source/patella)), and the proximal {{linktext|tibiofibular}} articulation.

The joint is stabilized by paired collateral ligaments which act to prevent abduction/adduction at the joint, as well as paired [cruciate ligaments](/source/cruciate_ligaments).  The [cranial cruciate ligament](/source/cranial_cruciate_ligament) and the [caudal cruciate ligament](/source/caudal_cruciate_ligament) restrict cranial and caudal translation (respectively) of the [tibia](/source/tibia) on the [femur](/source/femur). The cranial cruciate also resists over-extension and inward rotation, and is the most commonly damaged stifle ligament in dogs.

"Cushioning" of the joint is provided by two C-shaped pieces of cartilage called [menisci](/source/meniscus_(anatomy)) which sit between the medial and lateral condyles of the distal femur and the tibial plateau. The main biomechanical function of the menisci is probably to divide the joint into two functional units—the "femoromeniscal joint" for flexion/extension movements and the "meniscotibial joint" for rotation—a function analogous to that of the disc dividing the [temporomandibular](/source/temporomandibular) (jaw) joint. The menisci also contain nerve endings which are used to assist in [proprioception](/source/proprioception).

The menisci are attached via a variety of ligaments: two {{linktext|meniscotibial}} ligaments for each meniscus, the {{linktext|meniscofemoral}} from the lateral meniscus to the femur, the {{linktext|meniscocollateral}} from the medial meniscus to the medial collateral ligament, and the transverse ligament (or {{linktext|intermeniscal}}) which runs between the two menisci. 

There are between one and four [sesamoid](/source/sesamoid) bones associated with the stifle joint in different species. These sesamoids assist with the smooth movement of tendon/muscle over the joint. The most well-known sesamoid bone is the patella, more commonly known as the "knee cap". It is located cranially to the joint and sits in the trochlear groove of the femur. It guides the patellar ligament of the [quadriceps](/source/quadriceps) over the knee joint to its point of insertion on the tibia. Caudal to the joint, in the dog for example, are the two [fabella](/source/fabella)e, which lie in the two tendons of origin of [gastrocnemius](/source/gastrocnemius). Fourth, there is often a small sesamoid bone in the tendon of origin of [popliteus](/source/popliteus) in many species. Humans possess only the patella.

In horses and oxen, the distal part of the tendon of insertion of quadriceps ("below" the patella) is divided into three parts. An elaborate twisting movement of the patella allows the stifle to "lock" in extension when the medial portion of the tendon is "hooked" over the bulbous medial trochlear ridge of the distal femur. This locking mechanism enables these animals to sleep while standing up.

==References==
{{reflist}}

==External links==
{{Wiktionary|stifle}}

*[http://www.horses-and-horse-information.com/articles/0197stifl.shtml A stifling problem]
*[http://www.equinenaturaltherapy.com/equine_joints.htm Introduction to the types of joints in horses.]

Category:Animal anatomy
Category:Dog anatomy
Category:Horse anatomy
Category:Joints of the lower limb
Category:Skeletal system

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Adapted from the Wikipedia article [Stifle joint](https://en.wikipedia.org/wiki/Stifle_joint) by Wikipedia contributors ([contributor history](https://en.wikipedia.org/wiki/Stifle_joint?action=history)). Available under [Creative Commons Attribution-ShareAlike 4.0 International](https://creativecommons.org/licenses/by-sa/4.0/). Changes may have been made.