What Is TPLO Surgery? A Primer for New Surgeons

Why dogs need TPLO: cranial cruciate ligament disease

The cranial cruciate ligament (CrCL, the canine equivalent of the human ACL) is one of the main stabilizers of the stifle (knee). In dogs it usually fails through progressive degeneration rather than a single athletic injury, which is why partial tears often become complete ruptures and why many dogs eventually rupture the ligament in the other knee too.

Without a working CrCL, the tibia slides forward relative to the femur every time the dog puts weight on the leg. That instability causes pain, lameness, joint inflammation, progressive osteoarthritis, and often a tear of the medial meniscus.

• Typical history: hind-limb lameness that may be sudden or intermittent, stiffness after rest, sitting with the affected leg kicked out.
• Exam findings: cranial drawer and a positive tibial thrust (tibial compression) test, stifle effusion, medial buttress (firm swelling on the medial joint), sometimes a meniscal click.
• Radiographs: joint effusion (loss of the infrapatellar fat pad), osteophytes in chronic cases. The ligament itself is not visible on radiographs.

The biomechanics: tibial thrust and the sloped plateau

The top of the canine tibia (the tibial plateau) slopes backward. When the dog bears weight, compressive force travels through the joint; because the plateau is sloped, part of that force becomes a forward-directed shear force on the tibia called cranial tibial thrust. A healthy CrCL resists it. A ruptured CrCL cannot.

Barclay Slocum's insight in developing TPLO was that you do not have to replace the ligament if you remove the slope. Rotate the plateau until it is nearly perpendicular to the tibia's functional axis, and weight bearing no longer pushes the tibia forward. In vitro work by Warzee and colleagues showed that leveling the plateau to about 6.5° neutralized cranial tibial thrust, which is why most surgeons aim for a post-op angle of roughly 5°.

Before surgery: the radiograph and the preoperative plan

TPLO planning starts with a true mediolateral radiograph of the whole tibia, including the stifle and the tarsus (hock), with the femoral condyles superimposed and a calibration marker at the level of the bone. From that image the surgeon plans five things:

1. Calibration: convert pixels to millimeters so every measurement is real. See radiograph positioning and calibration.
2. TPA: place four landmarks (cranial and caudal plateau margins, the intercondylar eminence, and the center of the talus) and measure the angle.
3. Saw blade and osteotomy position: choose a blade radius that fits the proximal tibia and position the curved cut, usually centered near the intercondylar eminence, while leaving enough tibial tuberosity.
4. Rotation: calculate how far to rotate the plateau segment along the cut to reach the target angle. See TPLO rotation and saw blade selection.
5. Plate: template a plate size that fits the proximal segment and the tibial shaft. See choosing and templating a TPLO plate.

Done by hand with acetates and rotation charts, this takes around 30 minutes per case. For the full workflow, read how to plan a TPLO.

The surgery, step by step

Techniques vary between surgeons, but a typical TPLO follows this sequence:

1. Joint assessment. The stifle is explored by arthrotomy or arthroscopy. Torn ligament remnants are debrided and the medial meniscus is inspected; a torn meniscus is treated, usually by partial meniscectomy.
2. Approach and jig (optional). A medial approach exposes the proximal tibia. Some surgeons place a TPLO jig to hold alignment during the cut.
3. Osteotomy. A curved, biradial TPLO saw blade makes the radial cut through the proximal tibia at the planned position.
4. Rotation. The plateau segment is rotated along the cut by the planned distance, measured between reference marks on either side of the osteotomy, and held with a temporary pin.
5. Fixation. A TPLO locking plate is applied to the medial tibia with screws in the proximal segment and the shaft.
6. Post-op radiographs. Confirm the new TPA, the plate and screw positions, and that no screw enters the joint.

The post-op radiograph (shown at the top of this guide) is compared with the preoperative plan to confirm the plateau was leveled as intended.

Recovery and outcomes

Most dogs toe-touch within days and bear weight progressively over the following weeks. Activity is strictly restricted (leash walks only, no running, jumping or stairs) while the osteotomy heals, and recheck radiographs are usually taken around 8 weeks to confirm healing before activity is increased. Rehabilitation therapy is commonly used to rebuild muscle and range of motion.

TPLO is widely regarded as producing good to excellent long-term function in most dogs, including large and athletic breeds, which is a major reason it has become the most common CrCL procedure in referral practice.

Complications, and why planning matters

Reported complications include surgical site infection, tibial tuberosity fracture, fibular fracture, implant problems, patellar desmitis, and late meniscal tears. Several of these are influenced by decisions made during planning:

• Tibial tuberosity fracture is associated with osteotomy position and a thin remaining tuberosity. In a study of 468 TPLOs, planned cases had no tuberosity fractures in 172 surgeries versus 6.8% of free-hand cases (Collins and colleagues, 2014).
• Inadequate or excessive rotation leaves residual instability or over-corrects the plateau. A measured rotation distance, rather than an estimate, reduces that error.
• Poor implant fit (screws near the joint or the osteotomy) is easier to avoid when a true-size plate template has been checked before surgery.

Alternatives to TPLO