TPLO with rotation support
A closer look at rotational stability, how Dr. Wood decides whether extra support is appropriate, and what the evidence shows.
A decision based on your dog’s knee
Dr. Wood considers rotation support when important twisting remains after TPLO. It is not a routine addition to every TPLO. The final decision follows repeated examination and testing during surgery.
This guide builds on the comparison of TPLO and lateral suture repair. It explains the reasoning behind combining them in selected knees.
Why add a lateral suture to TPLO?
The cranial cruciate ligament runs diagonally across the knee joint. It helps limit forward movement of the shin bone and excessive internal rotation, and helps prevent the knee from overextending.
TPLO is designed mainly to reduce the forward sliding force in the upper shin during weight bearing, often called cranial tibial thrust. During a specialist assessment, Dr. Wood looks at both forward movement and rotation. Some knees can still twist abnormally after the forward movement has been reduced. This rotational instability is sometimes described as pivot shift.
An extracapsular brace, sometimes called an internal brace, adds support outside the joint to help control that twisting movement. Dr. Wood uses the Arthrex SwiveLock® anchor system.
How the final brace decision is made
This pattern may be especially relevant in a very recent, complete cruciate tear, before the body has formed stabilizing scar tissue, called fibrosis, around the knee. Experimental evidence supports this as a model of a very loose knee, but it does not mean every acute tear needs a brace.
The examination, imaging and early stability tests guide the plan. Dr. Wood decides whether to add the brace after testing the knee again during surgery.
Immediately after completing the TPLO, Dr. Wood tests the knee again to see how much rotational instability remains. He makes the final brace decision at that point and adjusts the operation if needed.
The decision is not determined by breed or body weight alone, and an extracapsular brace is not a standard addition to every TPLO.
Why preserve the muscle attachments?
Preserving important muscle attachmentsWhy preserve the pes anserinus?
The pes anserinus is where several substantial hamstring and adductor muscle-tendon attachments join the inside of the upper shin bone. Preserving it keeps these important muscles attached to the tibia. In a human high tibial osteotomy paper, the pull from these attachments was separated into backward and upward force components. The authors proposed that these forces help compress and stabilize the bone cut, while releasing the attachment could allow the lower bone segment to rotate outward.
Dr. Wood preserves this attachment when exposing the bone during TPLO. This muscle-sparing approach is intended to retain the muscles' natural contribution to stability around the bone cut.
This mechanical rationale is extrapolated from human knee surgery. It has not been proven to improve TPLO outcomes in dogs, and it does not replace an extracapsular brace when important pivot shift remains after TPLO.
When Dr. Wood assesses rotational stability
Dr. Wood uses a tibial pivot compression test as part of checking for abnormal forward movement and rotation. This identifies the pattern but does not make the final brace decision.
Dr. Wood repeats the stability assessment under anesthesia. He also inspects the meniscus, the cushion inside the knee, through a small opening into the joint and can adjust the surgical plan to the stability findings and condition of the meniscus.
After completing the TPLO and closing the joint and the tissue covering the preserved muscle attachments (pes fascia), Dr. Wood tests the knee again. He then makes the final decision about adding an extracapsular brace.
Read the evidence behind the assessment
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%.
The gait change often persisted at follow-up. In that same study, it disappeared over four to six months in four of the 15 affected knees.
This does not mean every dog needs an extracapsular brace. It explains why Dr. Wood tests for pivot shift after completing the TPLO. Remaining rotational instability can persist.
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. Dr. Wood adds 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 substantially more forward movement than intact knees. Adding lateral support reduced that movement.
In the external-rotation pivot test, average internal rotation was 27 degrees after TPLO, 15.7 degrees in intact knees and 12.1 degrees after added lateral support. These are laboratory measurements under a specific test, not normal walking.
Dr. Wood checks whether the usual tibial thrust has been controlled and assesses forward movement and twisting together before deciding whether a selected knee needs additional support.
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%).
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.
Questions to discuss at your consultation
- What pattern of knee instability did the examination show?
- What changes after the TPLO, and what movement remains?
- What would additional support be intended to address?
- How would it change the operation, risks or recovery plan?
Sources used for this guide
View the evidence sources
- American College of Veterinary Surgeons: Cranial Cruciate Ligament Disease
- Gatineau et al.: postoperative pivot shift after TPLO
- Lampart et al.: experimental evaluation of the tibial pivot compression test
- Husi et al.: biomechanical TPLO and TPLO-plus-augmentation comparison
- Wylie et al.: internal-brace placement and pivot-shift follow-up after TPLO
- Nakamura et al.: pes-preserving human high tibial osteotomy and proposed force components
- Yilmaz et al.: human high tibial osteotomy outcomes with and without pes release
- Arthrex Vet Systems: TPLO plate surgical technique with InternalBrace ligament augmentation
- Arthrex Vet Systems: TPLO InternalBrace augmentation using a SwiveLock anchor