How Do You Know If Your Dog Tore Their Acl? Symptoms and Diagnosis

If your dog is suddenly limping after running or shows dog hind leg lameness, they might have torn their ACL (Anterior Cruciate Ligament). Diagnosing a canine ACL tear requires looking closely at signs and getting a proper veterinary orthopedic assessment dog.

Spotting the Signs of a Canine ACL Tear

A torn ACL, also known as a canine cranial cruciate ligament rupture in dogs, is one of the most common knee injuries in dogs. This ligament keeps the shin bone (tibia) stable under the thigh bone (femur). When it tears, the knee becomes unstable.

Early Warning Signs of Knee Injury

Recognizing dog knee injury signs early can lead to faster relief for your pet. Often, the injury happens during play or exercise, but sometimes it seems to come out of nowhere.

Here are key canine ACL tear symptoms to watch for:

Sudden Lameness: Your dog might suddenly start holding up a rear leg. This is a very common sign.
Mild Limping That Worsens: Sometimes, the limping starts small. Your dog might seem fine after a short rest, only to get worse later. This is often seen when dogs have a partial tear first.
“Toe-Touching”: Your dog may only put the very tip of their foot on the ground. They bear very little weight on the leg.
Stiffness: Especially after resting, your dog might seem stiff when getting up or starting to move.

Advanced or Chronic Symptoms

If the tear is complete or if it has been present for a while, you might notice more obvious signs. These are often clear signs dog needs TPLO surgery down the road.

Obvious Favoring: The dog shows definite dog favoring back leg movement. They might shift their weight to their other three legs.
Swelling: You might feel or see swelling around the knee joint. This often indicates inflammation and fluid buildup.
Pain When Touched: Your dog may pull the leg away or whine if you gently touch or try to move the knee joint.
Decreased Activity: They stop jumping, playing fetch, or going up and down stairs as much.

Severity of Tear	Common Observation	Duration of Symptoms
Partial Tear	Intermittent limping, slight stiffness	Days to weeks
Complete Tear	Sudden, severe lameness, holding leg up	Immediate and constant
Chronic Tear	Muscle wasting, difficulty standing fully	Months to years

The Physical Examination: What the Vet Looks For

When you suspect dog hind leg lameness, a trip to the vet is necessary. The vet will perform a thorough physical check, focusing heavily on the knee joint. This part of the exam is crucial for diagnosing dog ACL tear.

Assessing Muscle Wasting

The vet will often look at both rear legs side-by-side. If one leg has a torn ACL, the dog uses that leg less. Over time, the muscles in that leg shrink. This is called muscle atrophy or wasting. It’s a strong indicator that the leg has been weak for some time.

Palpation and Range of Motion

The veterinarian gently feels (palpates) the dog’s leg. They check for heat or pain around the knee area. They also check how far the knee joint can bend and straighten. Reduced range of motion often points to pain or internal damage.

The Key Test: The Drawer Sign

The most important part of the veterinary orthopedic assessment dog for an ACL tear is checking for instability. The vet performs a test called the “Cranial Tibial Thrust” or the “Drawer Sign.”

What is the Drawer Sign? The vet holds the dog’s thigh steady with one hand. They place the other hand on the lower leg (shin). They gently push the tibia forward and pull the femur back.
What Happens with a Tear? If the ACL is torn, the shin bone slides forward too easily compared to the thigh bone. This sliding motion is the “positive drawer sign.” It proves the ligament is no longer holding the joint stable.
Why it matters: If the tear is old and has caused arthritis, the knee might be too stiff for the vet to feel the drawer sign. In these cases, other tests or imaging are needed.

Advanced Diagnostic Tools for Confirmation

While the physical exam is very helpful, vets often use other tools to confirm the diagnosis and plan the best treatment, especially before deciding on signs dog needs TPLO surgery.

X-Rays (Radiographs)

X-rays are vital. They do not show the soft tissue (like the ligament itself) clearly. However, they show the bones.

Arthritis Signs: X-rays reveal bone changes caused by chronic instability, such as bone spurs (osteophytes). This confirms arthritis related to the tear.
Tibial Plateau Slope: X-rays allow the vet to measure the angle of the top surface of the shin bone. This angle is called the tibial plateau slope. A steeper slope makes the knee naturally unstable. This measurement is key if signs dog needs TPLO surgery are being considered.
Ruling Out Other Issues: X-rays help ensure the lameness isn’t caused by a broken bone or severe joint infection.

Sedation and Advanced Imaging

Sometimes, a dog is too tense or painful for the vet to perform a complete drawer test while awake. In these cases, a light sedation or general anesthesia allows for a very precise veterinary orthopedic assessment dog.

Under sedation, the vet can:

Confirm a positive drawer sign.
Thoroughly check for a torn meniscus (the shock absorber cartilage in the knee). A torn meniscus often happens along with an ACL tear.

MRI and CT Scans

In rare or complex cases, Magnetic Resonance Imaging (MRI) or Computed Tomography (CT) scans might be used. These scans provide detailed images of the soft tissues, showing the ligament tear and meniscus damage directly. These are usually only done at specialized surgical centers.

What Causes a Dog to Tear Their ACL?

It is helpful to know why this injury happens when looking at dog knee injury signs. The causes usually fall into two main categories: acute injury or chronic degeneration.

Acute Injury (Sudden Trauma)

This happens suddenly, often during vigorous activity.

Twisting or Pivoting: A dog running fast and then suddenly changing direction puts extreme stress on the knee.
Slipping: Misstepping on a slippery floor or during rough play can cause a sudden tear.
Jumping Down: Landing awkwardly after jumping off furniture or a deck can cause the tear.

Chronic Degeneration (Wear and Tear)

This is far more common, especially in middle-aged or older, larger dogs. The ligament weakens over time due to small stresses until it finally snaps.

Genetics and Anatomy: Some breeds are predisposed (like Labrador Retrievers, Rottweilers, and Bulldogs). The shape of the shin bone (a steep tibial plateau) puts more stress on the ligament, leading to a faster breakdown.
Obesity: Extra weight puts constant, high pressure on the knee joints, speeding up ligament weakening.
Osteoarthritis: Pre-existing mild arthritis weakens the ligament structure.

A crucial note: If your dog tears one ACL, they have a high risk (up to 60%) of tearing the other one within two years. This is due to shared risk factors like genetics and weight distribution.

Treatment Options for a Canine CCL Rupture

Once a canine cranial cruciate ligament rupture is confirmed, treatment depends on the dog’s size, age, activity level, and the severity of the arthritis present. Treatment aims to stabilize the knee joint.

Non-Surgical Management

For very small, less active dogs, or those who cannot undergo anesthesia, non-surgical routes are sometimes tried. This is generally not recommended for dogs over 30 pounds.

Non-surgical care focuses on managing pain and inflammation while letting scar tissue stabilize the joint over time.

Strict Rest: Very limited leash walks only. No running, jumping, or stairs for several weeks or months.
Weight Management: Losing excess weight is essential for any treatment plan.
Medication: Anti-inflammatory drugs (NSAIDs) help manage pain and reduce dog knee swelling treatment.
Physical Therapy: Controlled exercise later in recovery helps rebuild muscle strength around the joint.

Surgical Stabilization

For most dogs, surgery provides the best long-term outcome by restoring knee stability immediately. This is often the answer when you see clear signs dog needs TPLO surgery.

There are two main types of surgery:

1. Lateral Suture Technique (Extracapsular Repair)

This method mimics the function of the ACL by placing a strong suture material outside the joint capsule to act as a temporary band, preventing the tibia from sliding forward.

Use Case: Best for small dogs (under 25 pounds) or as a temporary fix.
Drawback: The suture material can stretch over time, especially in larger, active dogs, and it does not change the biomechanics of the knee joint itself.

2. Tibial Plateau Leveling Osteotomy (TPLO)

TPLO is one of the most common and successful procedures for larger, active dogs experiencing dog limping after running or severe instability. TPLO changes the actual mechanics of the knee.

The Goal: TPLO cuts the top part of the shin bone (the tibial plateau) and rotates it to a flatter angle. This rotation removes the forward slope. Once the slope is flatter, the dog’s own muscles and tendons stabilize the knee without needing the ACL.
When is TPLO necessary? When the veterinary orthopedic assessment dog shows a significant drawer sign and X-rays show a steep tibial plateau slope, TPLO is often the preferred choice. It aims to restore near-normal function.
Recovery: Recovery is intensive, usually involving 8-12 weeks of restricted activity.

3. Tibial Tuberosity Advancement (TTA)

TTA is another surgical technique that changes the forces within the knee joint. It moves the attachment point of the patellar tendon forward. This also neutralizes the forward thrust that causes instability. TTA is often chosen for certain breeds or specific knee angles.

Post-Diagnosis Care and Recovery

Successful recovery from a canine ACL tear hinges on strict post-operative care, whether surgery was performed or not. Improper recovery can lead to chronic pain or a secondary tear.

Managing Inflammation and Pain

Immediately after injury or surgery, controlling swelling is vital for dog knee swelling treatment.

Cold Therapy: Applying ice packs to the joint for short intervals (10-15 minutes) several times a day helps reduce initial swelling and pain.
Medication: Your vet will prescribe pain relievers and anti-inflammatories. It is critical to give these exactly as directed. Never give human pain medication to dogs.

Activity Restriction: The Long Road Back

This is the hardest part for many owners. Healing the joint takes time, and pushing too hard too soon can ruin the surgery or delay natural healing.

Initial Weeks (0-4): Strict crate rest or very small, controlled leash walks only for bathroom breaks. No running, jumping, stairs, or rough play.
Mid-Recovery (4-8 Weeks): Gradual introduction of short, slow leash walks. Focus on controlled movement, not distance.
Late Recovery (8+ Weeks): Depending on X-rays (for TPLO), more activity can begin. This often includes hydrotherapy (swimming or underwater treadmill) to build muscle without joint impact.

Physical Rehabilitation (Rehab)

Rehab is crucial for maximizing the success of any treatment for dog hind leg lameness. A certified canine rehabilitation practitioner (CCRP) can guide this process.

Rehab helps:

Reduce scar tissue formation.
Restore full range of motion.
Build strong, supporting muscles to protect the knee.
Help the dog overcome the habit of dog favoring back leg.

Breed Predisposition and Risk Factors

While any dog can tear a ligament, certain factors increase the risk of developing dog knee injury signs. Recognizing these factors can prompt owners to take preventative steps.

Breed Group	Common Issues	Example Breeds
Large/Giant Breeds	Steep tibial plateau slope (biomechanical risk)	Rottweilers, Mastiffs, Newfoundlands
Medium/Active Breeds	High impact during sports/work	Labrador Retrievers, Boxers, Siberian Huskies
Small Breeds	Ligament weakness, sometimes genetic	Yorkshire Terriers, Cocker Spaniels

The Role of Weight Management

Obesity is perhaps the single most controllable factor in canine orthopedic health. Excess body weight increases the load on the joints with every step, dramatically speeding up the wear and tear that leads to a canine cranial cruciate ligament rupture. Maintaining a lean body condition score is the best way to reduce the risk of a tear or a secondary tear.

Differentiating ACL Tear Pain from Other Causes

When a dog shows dog limping after running, owners often jump to the conclusion of an ACL tear. However, several other issues can cause similar dog hind leg lameness. This is why professional diagnosing dog ACL tear is so important.

Other possibilities include:

Muscle Strain: Simple pulling of a hamstring or quadriceps muscle. This usually resolves quickly with rest.
Hip Dysplasia: Pain originating higher up in the hip joint can cause the dog to move the rear leg strangely, mimicking knee pain.
Meniscal Tear Only: Sometimes the meniscus is torn, but the ACL is intact. This can cause clicking or intermittent lameness.
Luxating Patella (Trick Knee): More common in small breeds, the kneecap slips out of place. This causes a skipping gait rather than the consistent lameness of a full ACL tear.

A proper veterinary orthopedic assessment dog will systematically rule out these other conditions before finalizing the diagnosing dog ACL tear.

Living After ACL Repair: Long-Term Outlook

The long-term outlook after successful surgery, particularly TPLO, is generally very positive. Most dogs return to a good quality of life and can resume normal activities, though perhaps with less high-impact agility than before the injury.

If surgery is not performed, the dog will likely develop severe, chronic osteoarthritis in that knee within a year or two. This leads to persistent discomfort, stiffness, and the dog continuing to show dog favoring back leg habits, which places extra stress on the other joints.

Owners must monitor for signs of arthritis developing in the non-injured leg, as this often means the owner should start thinking proactively about preventative care or earlier intervention for that knee as well. Early intervention for dog knee injury signs often yields the best results.

Frequently Asked Questions (FAQ)

How quickly does a dog need surgery after tearing their ACL?

While immediate surgery is ideal for severe pain, many dogs do well waiting a few days to a week, especially if strict rest is enforced. However, the longer the joint remains unstable, the more damage occurs to the meniscus and the faster arthritis develops. If severe instability (positive drawer sign) is present, surgery is generally recommended sooner rather than later.

Can my dog live happily without ACL surgery?

For small dogs (under 20 pounds) or very elderly dogs with low activity levels, they can sometimes manage without surgery through strict weight control and long-term pain management. However, for medium to large breeds, instability leads quickly to secondary arthritis and chronic pain, making surgery the preferred long-term solution for maintaining mobility and reducing the need for constant medication.

How much does TPLO surgery cost?

The cost for TPLO surgery varies widely based on location, the specific clinic, and whether additional procedures (like a simultaneous meniscus trim) are needed. Generally, TPLO is expensive, often ranging from \$3,000 to \$6,000 or more per knee, not including pre-surgical bloodwork, X-rays, and post-operative medication and rehab.

How long until my dog stops favoring their back leg?

If surgery is performed, most dogs start putting weight on the leg within 1 to 3 weeks, though they will still be dog favoring back leg somewhat due to muscle soreness and precaution. It usually takes 8 to 12 weeks of strict rehab before the limp is almost completely gone and the dog trusts the leg again. Full recovery and muscle mass rebuilding can take six months to a year.

Are X-rays sufficient for diagnosing dog ACL tear?

X-rays are essential for planning surgery (measuring the tibial slope) and checking for arthritis, but they cannot visualize the ACL itself. The primary tool for diagnosing dog ACL tear remains the physical examination, specifically the drawer test, sometimes performed under sedation.