Cruciate disease is one of the most common reasons dogs develop knee pain and back-leg lameness.

The cruciate ligament is one of the main stabilizers inside the knee. In many dogs, it does not simply snap during one accident. It often weakens gradually, a bit like a rope that is fraying. At some point it may partially tear or completely tear.

Once the ligament is no longer doing its job, the knee can move abnormally when your dog stands or walks. That abnormal motion creates pain and inflammation inside the joint, and over time it contributes to osteoarthritis.

The meniscus is a C-shaped cushion, a bit like a shock absorber, inside the knee. It sits between the thigh bone and shin bone and helps distribute load when your dog stands, walks, and turns.

When the cruciate ligament is damaged, the knee can move abnormally. That abnormal motion can pinch or tear the meniscus. A meniscal tear can add pain, catching, clicking, or a more persistent limp.

A click can make us more suspicious of a meniscal tear, but many dogs with meniscal injury do not have an obvious click. If TPLO surgery is performed, the meniscus is checked during surgery and treated if needed.

During the consult, I assess the whole picture: how your dog uses the leg, where the knee is painful, how the joint moves, and whether the knee shows instability.

• How your dog stands, walks, sits, turns, and uses the sore leg.
• Pain, swelling, thickening, range of motion, and comfort through the knee.
• Meniscal clues, such as clicking, catching, joint discomfort, or a limp that does not fit the rest of the exam.
• Standard cruciate instability checks, such as the ones shown here.
• Rotational or pivot instability, assessed with the tibial pivot compression test.
• The kneecap, hips, opposite knee, alignment, and body condition, because these can affect diagnosis, treatment planning, and recovery.
• Sedated examination may help when the physical exam is limited or unclear.

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Radiographs help look for other causes of pain and show bone and joint changes around the knee.

Diagnostic radiograph TPLO planning radiograph

The diagnosis of knee instability is primarily made on the orthopedic exam. Radiographs are still important, but they answer different questions: they help look for other causes of pain and provide the measurements needed for surgical planning.

• Radiographs can show arthritis, joint swelling, bone shape, and other changes around the knee, and help rule out other bone or joint problems, including bone disease or neoplasia, that could change the plan.
• For TPLO planning, the X-rays need a calibration marker, often a calibration ball, so measurements are accurate.
• Calibrated planning radiographs help choose plate size, screw lengths, saw blade size, cut placement, and how much the bone segment should be rotated.
• Radiographs do not directly show the cruciate ligament or every meniscal injury.
• Some details, such as meniscal injury or cartilage changes, may only be assessed more directly during surgery or joint inspection when available.

The cruciate ligament normally helps control abnormal sliding or shearing motion in the knee. When it is damaged, the knee becomes painful and unstable, especially when your dog bears weight.

TPLO stands for tibial plateau leveling osteotomy. Instead of replacing the torn cruciate ligament, TPLO changes the slope of the top of the tibia with a controlled curved bone cut. In owner terms, I often describe it as a controlled, carefully planned bone cut, almost like a controlled fracture. The bone segment is rotated into a new planned position and held with a plate and screws while it heals. This changes how the knee bears weight so it can be functionally more stable.

Every TPLO is performed with a muscle-sparing, or pes-sparing, approach. The pes anserinus is where several hamstring and adductor muscle-tendon attachments meet on the inside of the upper shin bone, close to where TPLO is performed. Rather than routinely releasing these muscle attachments for exposure, they are preserved while the planned bone cut, rotation, plate placement, and screw fixation are performed.

Surgical photo comparisonIntra-operative views before closure; tap to compare exposure.

These before-closure images compare a traditional exposure with the muscle-sparing approach, showing the difference in how much of the muscle attachment is released to access the upper tibia.

This approach is extrapolated from human high tibial osteotomy literature, where preserving the pes anserinus has been associated with maintained alignment correction, earlier bone healing, and better early function. The same principle guides the technique here: accurate TPLO surgery with deliberate protection of the muscle attachments around the bone.

TPLO does not replace the torn ligament, and it does not remove all arthritis. It is a bone surgery: a controlled cut is made in the top of the shin bone, then the bone is stabilized while it heals.

The important point is that TPLO can change how pressure is carried through the meniscus. In studies that measure pressure inside the knee, the pattern after TPLO can look more like a knee before the cruciate ligament was torn than a knee with a torn ligament.

Pressure-map exampleHow knee loading changes before and after TPLO.

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Torn ligament

Before injury pressure map Torn ligament pressure map After TPLO pressure map

TPLO changes the way weight passes through the knee. This can help reduce the abnormal pinching forces on the meniscus. That matters because meniscus that remains stable can still help cushion and protect the joint.

If there is a displaced or unstable tear, especially a bucket-handle tear that can catch in the joint, the damaged portion is treated. A stable meniscus is always spared.

Early recovery focuses on incision protection, cone or recovery-collar use, toileting-only leash walks, pain control, medication monitoring, and preventing jumping, slipping, running, rough play, or off-leash activity. Some soreness, swelling, bruising, tiredness, or mild lameness can occur early, but the overall trend should be toward comfort and controlled limb use.

The rehab plan adds walking targets and simple exercises by stage. Stairs are treated as controlled household access, not exercise. Running, jumping, trotting, rough play, sport, and off-leash activity wait until healing has been assessed and the next stage has been cleared.

Recheck X-rays are planned at 10–12 weeks to assess bone healing and implant position before activity is advanced. The exact date within that window can change depending on the dog, comfort, progress, and surgeon review.

The TPLO rehab package includes the detailed Week 8 recheck plan and after-clearance activity progression.

After radiographic and clinical healing, activity is gradually increased. Running, jumping, stair exercise, rough play, and sport should wait until cleared.