Stifle extension results in differential tensile forces developing between abaxial and axial components of the cranial meniscotibial ligament of the equine medial meniscus: a mechanistic explanation for meniscal tear patterns.

This research explores how full extension of a horse’s stifle, or knee joint, increases the tension in certain parts of the medial meniscus ligament, which could explain common injury patterns in this area.

Research Objectives and Methodology

The study aimed to uncover functional-anatomical characteristics of the attachment of the medial meniscus (MM), a particular cartilage in a horse’s knee, to help understand how common injury patterns develop. The main objective was to examine how a full extension of the stifle (the horse equivalent of the human knee) significantly increases the tensile forces in the cranial meniscotibial ligament (CrMTL) of the MM.

• The research involved studying the impact of different angles (160°, 150°, 140°, and 130°) of the femorotibial, the knee joint, on the tension in the axial and abaxial sections of the CrMTL. The testing was performed on six mature cadaver stifles using a force probe.
• Three more specimens were used for the histological examination of the CrMTL structure and its connection to the MM’s cranial horn.

Key Research Findings

There were several significant findings from this research:

• Full stifle extension (160°) led to significantly more tension in the abaxial part of the CrMTL compared to the axial part.
• Tension in the abaxial part of the CrMTL significantly increased between 150° and 160° of stifle extension.
• The CrMTL contains two functional components that become more visually distinct as the stifle is extended. When observed histologically, these components are divided by a highly vascularised, less organised connective tissue cleft, which becomes less prominent at the junction of the ligament and MM’s cranial horn.

Conclusion

The findings showed a four-fold difference in tension between the two functional components of the CrMTL when the stifle was fully extended. This suggests that the functional anatomy of the CrMTL might make this region more susceptible to injury during stifle hyperextension. The study then, provides an explanation for the common meniscal tear patterns reported in horses. The understanding of this mechanism could contribute to the development of better prevention measures and treatments for horses with stifle injuries.