Clock Plots are visuals that illustrate asymmetry indices, which may help practitioners during lameness evaluations. In Equi-Pro®, there are two Clock Plots:

• The left Clock Plot, which shows the front limb MinDiff and MaxDiff asymmetry parameters for the head and withers.
• The right Clock Plot, which shows the hind limb asymmetry parameters MinDiff and MaxDiff for sacrum and the HipHike (HH) swing and stance components.

Figure 1: Example Clock Plots in Equi-Pro

The MinDiff and MaxDiff values of the head, withers and sacrum are presented related to their clinical meaning: Impact and/or Push-Off asymmetries. MinDiff is usually related to Impact lameness while MaxDiff asymmetries are often present in Push-Off lameness representations.

In case of unilateral hind limb lameness, research has shown that both HipHike swing and stance components are present and pointing towards the lame limb [Starke and May, 2021].

To graphically illustrate the above concepts, each Clock Plot is divided into four quadrants representing the affected limb (Left or Right) and the asymmetry type (Impact or Push-Off).

Video demonstrating how Clock Plots are created

The video below shows how the Clock Plots are created in the Equi-Pro application starting from the MinDiff and MaxDiff values of the head, withers and sacrum, and including the HipHike stance and swing.

To understand the definitions and the methods used to compute the upper-body asymmetry parameters MinDiff, MaxDiff and HipHike in the Equi-Pro application, please visit the MinDiff, MaxDiff, Symmetry Index and HipHike technical article.

The following two examples explain the Horse Plots visuals and associated Clock Plots.

Example 1

The analysis of the plots from from Figure 2 reveals the following information:

• The horse presents the same amount of MinDiff and MaxDiff at the head level, which leads to an average vector pointing towards the Right front limb, between Impact and Push-Off.
• The Withers points towards the Right limb too and follows a distribution similar with the head.
• The sacrum presents a larger MinDiff towards the Right hind limb while the MaxDiff components alternate between Left and Right hind limbs, with a majority towards the Right hind limb. Therefore, the sacrum Clock Plot points towards a asymmetry with almost only an Impact component.
• The HipHike swing points towards the Right hind limb while the HipHike stance also alternates between Left and Right. Therefore, the HH vector points towards a mainly HH swing components on the right side of the Clock Plot.

Figure 2 – First example of Horse Plots visuals and associated Clock Plots. On the left clock plot, the MinDiff and MaxDiff of the head (pink) and withers (blue) sensors are plotted to illustrate the Impact and Push-Off components of the front limb asymmetry patterns. On the right clock plot, the MinDiff and MaxDiff of the sacrum sensor (green) are plotted to illustrate the Impact and Push-Off components of hind limb asymmetry patterns, together with the HikeHike (HH) stance and swing (yellow).

Example 2

The analysis of the plots from from Figure 3 reveals the following information:

• The horse presents bilateral Push-Off (MaxDiff) and mainly unilateral Left Impact (MinDiff) component for the head sensor.
• The resulting front limb pattern clock plot points towards Left asymmetry with a major Impact component.
• The Withers patterns follows the head, pointing towards a Left front Impact (MinDiff) component.
• The Sacrum presents a mainly Right hind Push-Off and Left hind Impact pattern.
• The HH mainly points towards a Right hind HH swing component.

Figure 3 – Second example of Horse Plots visuals and associated Clock Plots. On the left clock plot, the MinDiff and MaxDiff of the head (pink) and withers (blue, visible on the bottom panel when hiding Head) sensors are plotted to illustrate the Impact and Push-Off components of the front limb asymmetry patterns. On the right clock plot, the MinDiff and MaxDiff of the sacrum sensor (green, visible on the bottom panel when hiding the HipHike) are plotted to illustrate the Impact and Push-Off components of hind limb asymmetry patterns, together with the HikeHike (HH) stance and swing (yellow).