TPLO, lateral suture, or both?

It does not always settle on its own

Persistent rotational instability after TPLO was uncommon in one retrospective study: it was identified after 15 of 476 procedures, or 3.1%.

However, when pivot shift did occur, it did not always resolve by itself. A later study reported that it disappeared over four to six months in only four of 14 affected dogs.

This does not mean every dog needs an extracapsular brace. It explains why I test for pivot shift after completing the TPLO rather than assuming that any remaining rotational instability will settle on its own.

The pivot test looks beyond tibial thrust

The standard tibial compression test, often called the tibial thrust test, mainly asks whether loading the knee causes the upper shin bone to move abnormally forward.

The tibial pivot compression test is not another name for the tibial thrust test. I perform it by adding external rotation and sideways pressure, called valgus stress, before applying compression. This assesses whether the knee moves forward and rotates at the same time.

In the first ten-limb laboratory study, the pivot test produced the greatest forward movement and internal rotation among the three tests examined.

In a second ten-limb study, knees treated with TPLO alone, without an extracapsular brace, appeared stable during the standard tibial-thrust test. Under deliberate pivot testing, however, they showed approximately six times more forward movement than intact knees. Adding the brace reduced this movement by approximately fourfold and returned the tested mechanics closer to the intact knee.

During the same pivot test, knees after TPLO alone rotated an average of 27 degrees. This was about 72% more than intact knees at 15.7 degrees. Adding the brace reduced that rotation by approximately 55% and returned it close to the intact range.

This is why I do not assess a TPLO only by confirming that the usual tibial thrust has been controlled. I also assess coupled forward and rotational instability before deciding whether a selected knee needs additional support.

Important limit: these findings came from deliberate rotational loading of ten cadaver limbs in each study. They do not describe normal walking, prove that every living dog has this movement after TPLO, or mean that every TPLO needs an extracapsular brace.

How the brace is intended to mimic ligament function

Parts of the normal cruciate ligament are close to isometric: their attachment points remain almost the same distance apart as the knee bends and straightens. Research has also identified corresponding isometric regions on the outside of the knee. The extracapsular brace is anchored at these external points so it follows a similar length pattern and can mimic part of the ligament's stabilizing action from outside the joint.

A 2025 retrospective study examined 39 dogs and 46 knees treated with TPLO plus an extracapsular brace. These were selected knees in which pivot shift remained after TPLO. They were not routine TPLO patients.

Thirty-three knees returned for examination at six weeks. Pivot-shift severity improved in 30 of 33 knees (90.9%), no pivot shift could be detected in 23 of 33 knees (69.7%), and lameness improved in 32 of 33 knees (96.7%).

Important limit: there was no TPLO-only control group. Only 33 of 46 knees had the six-week assessment, and the same surgeon who performed the operations assessed the dogs without blinding. Scar-tissue formation may also have contributed to the improvement. The study cannot prove that the brace caused the clinical improvement or that every TPLO benefits from one.