A working reference for the measurements, angles, ratios, and protocols you'll see in Laminitis Tool. Each term has a short definition followed by the clinical context. Cross-references link related concepts.
The horse's body weight in kilograms. Drives the Turner ratio (BW over solar area), which informs the Shore-A hardness recommendation for the shoeing surface.
A heavier horse produces more load per unit of solar area, which calls for a firmer shoeing surface to avoid the surface conforming excessively. The tool uses BW alongside hoof length and hoof width to compute the Turner ratio and pick a Shore-A target.
Coffin Bone Position, the caudal palmar process of P3. When CBP exceeds 30 mm, the tool derives the centre of rotation as CBP times 1.30 (Caldwell datum).
CBP is a radiographic landmark that gives an alternative reference for the centre of rotation when the DIPJ is hard to identify radiographically. In the app, selecting CBP as the CoR source switches the CoR derivation to the CBP-based formula.
The compound palmar angle, the palmar angle of P3 combined with the conformation angle to produce a clinically actionable prescription angle (Caldwell and Madden 2025).
A horse with a normal radiographic palmar angle but a non-vertical conformation experiences a different mechanical environment from one with the same PA but vertical conformation. The compound PA accounts for this. The tool computes and applies it automatically when CA is non-zero.
Limb-axis offset from vertical measured on the dorsopalmar view. Combined with palmar angle to produce the compound PA used in prescription.
CA is positive when the limb axis deviates in one direction and negative in the other. Zero means a vertical limb. The tool uses CA alongside the sagittal palmar angle to derive the compound PA.
Centre of Pressure, the distance from the heel bulb where the ground reaction force resultant acts on the foot. Target ratio CoP over SL is approximately 0.385.
CoP is a primary biomechanical target for any farriery intervention. When CoP sits too far forward relative to SL, the foot is loaded predominantly at the toe; too far back and the heels take excessive load. The prescription drives CoP toward 0.385 of SL.
Centre of Rotation, the centre of the distal interphalangeal joint (DIPJ). Target ratio CoR over SL approximately 0.492 when auto-derived, or measured from radiograph or CBP.
CoR is where the foot pivots during locomotion. It is the second primary biomechanical target alongside CoP. The tool offers four CoR sources: auto (SL times 0.492), radiograph (measured DIPJ), CBP estimate (CBP times 1.30), or manual entry.
Dorsal Hoof Wall Angle, the external angle of the dorsal hoof wall to the ground. Reference range 50 to 54 degrees in a normal foot.
DHWA is measured externally with a protractor or gauge against a level ground surface. In a laminitis case with rotation, the DHWA may diverge from the P3 angle, and this divergence is part of what the tool quantifies.
The width of the hoof capsule on the dorsopalmar (DP) radiographic view, measured level with the distal P3.
Combined with DP P3 length, the difference (capsule minus P3) reveals mediolateral asymmetry. A symmetric foot has capsule width approximately equal to P3 width; asymmetry indicates lateral or medial loading.
The width of P3 itself on the dorsopalmar view. Used with capsule width to derive mediolateral asymmetry (xDW minus xDP).
The heel-elevation prescription per Steward and O'Grady (AAEP 2007 and 2009). Driven by palmar angle, sole depth, and rotation thresholds.
F9 raises the palmar aspect of the foot to take tension off the deep digital flexor tendon, reducing the rotational moment on a compromised laminar interface. The tool returns F9 in millimetres and the corresponding wedge angle.
Capsule asymmetry in millimetres on the DP view. Drives the rim-pad wedge specification on the affected (medial or lateral) side.
A horse loaded asymmetrically develops a wider capsule on the loaded side. The tool measures the asymmetry and specifies a rim-pad wedge on the unloaded side to redistribute load.
A five-criterion modified version of the Obel grading scale: weight shifting, foot lifting, gait at walk, gait at controlled lift, and the two-criterion original Obel. Auto-computes the Obel grade.
The original Obel scale (1948) is a subjective five-point lameness scale (0 to 4). The modified version decomposes the assessment into five sub-criteria, each scored 0 to 2, then aggregates to an Obel grade. Reduces inter-observer variance.
The angle between the dorsal surface of P3 and the dorsal hoof wall, measured on the lateromedial (LM) radiograph. Pathological when greater than zero in a laminitis context.
Rotation indicates laminar failure: the dorsal lamellae have detached enough that P3 has rotated away from the hoof wall. Mild rotation is 5 degrees or less, moderate is 5 to 11, severe greater than 11.
The distance the extensor process of P3 has dropped below the proximal coronary band. Greater than 5 mm is significant; greater than 15 mm is grave.
Sinking indicates circumferential laminar failure, distinct from the dorsal-only failure that drives rotation. A horse can rotate without sinking, sink without rotating, or both. The tool's prognosis function treats sinking as the more serious of the two.
The angle of the palmar (rear) surface of P3 to the ground. Drives the F9 heel-elevation prescription. Reference range approximately 3 to 8 degrees.
A negative or very low PA increases tension in the deep digital flexor tendon and the rotational moment on a compromised laminar interface. F9 raises PA back into the safe range without over-elevating, which would introduce its own problems.
The heel-buttress to toe-pillar distance on the lateromedial view. Drives every ratio the tool uses (CoP over SL, CoR over SL, CC over SL).
SL is the scaling factor for the whole sagittal-plane analysis. Two horses with the same absolute CoP measurement but different SL values are in very different biomechanical situations; the ratios normalise this.
The durometer hardness of the shoeing surface in contact with the sole. Lower values are softer and more conforming.
The tool recommends a Shore-A target based on the Turner ratio. A heavy horse on a soft surface compresses the surface excessively and loses the mechanical advantage; a light horse on a hard surface gets no conformity. The recommendation balances both.
The radiographic distance from the solar margin of P3 to the ground surface. Reference greater than or equal to 15 mm; less than 10 mm indicates impending or active solar penetration.
Sole depth is the protective buffer between P3 and the ground. When it drops below 10 mm, P3 is at risk of penetrating the sole, an emergency state that escalates the prescription pathway.
The angle of the solar surface of P3 relative to ground. Reference range approximately 3 to 8 degrees.
TSA gives a single-number summary of P3 attitude. It tracks closely with palmar angle in a normal foot but can diverge in a compromised foot, particularly with localised sinking.
Body weight divided by solar area. Used to select the appropriate Shore-A hardness for the rim pad and shoeing surface.
The ratio expresses the load per unit area that the shoeing surface must support. The tool maps the ratio to a Shore-A recommendation calibrated against the rim-pad and shoeing-surface combinations used in field practice.
The target palmar angle following deep digital flexor tenotomy. Specification range 3 to 5 degrees; default 5 degrees.
A tenotomy removes the tendon's rotational pull on P3, but the foot still needs an appropriate mechanical environment afterwards. The post-tenotomy PA target sits in a tighter range than the F9 prescription because the tendon contribution is no longer available to absorb deviation.
Want to see these in action? Open the five reference scenarios to load real values into the live tool and see how each measurement feeds into the prescription.