A torn ACL (anterior cruciate ligament) in dogs is a common injury, especially in active or older pets. The ACL, also known as the CCL (cranial cruciate ligament) in dogs, plays a critical role in stabilizing the knee joint. When this ligament tears or ruptures, it can cause pain, mobility issues, and long-term complications if left untreated. Early recognition of the symptoms is key to ensuring your dog gets the proper treatment and recovery time.
In this guide, we will cover the common signs and symptoms of a torn ACL in dogs, so you can act quickly and get your pet the care they need.
1. Limping or Lameness in the Hind Leg
One of the most noticeable symptoms of a torn ACL is limping or lameness in the dog’s hind leg. The injury usually affects one leg at a time, though it’s possible for a dog to tear both ACLs over time. The limp may initially appear intermittent, worsening after exercise or activity. Your dog may be able to walk or run, but the injured leg will be used less and appear weak.
Over time, the limp may become more consistent as the condition progresses. If your dog shows signs of limping after jumping, playing, or walking, a torn ACL may be the cause. If the injury is severe, the dog may be unable to put weight on the affected leg at all.
2. Stiffness or Difficulty Moving
A torn ACL can cause stiffness and discomfort in your dog’s hind leg, especially after periods of rest or inactivity. Your dog may show signs of difficulty getting up from a resting position or walking for long distances. In some cases, the joint may become swollen, further hindering movement and making the dog reluctant to engage in normal activities.
Stiffness is often most apparent in the morning or after a nap when your dog has been inactive for an extended period. If your dog seems to have a hard time moving around, it’s important to evaluate their legs for any signs of injury, particularly in the knee joint.
3. Swelling in the Knee Area
Swelling around the knee is a common sign of a torn ACL in dogs. When the ligament is damaged, fluid can accumulate in the joint, leading to inflammation and visible swelling. This swelling may be more noticeable in the first few hours or days following the injury.
In some cases, the swelling may subside slightly, but it can return with further activity or strain on the injured leg. If the swelling persists or worsens, it’s essential to seek veterinary attention, as this could be a sign of joint instability or further ligament damage.
4. Pain or Sensitivity in the Leg
Dogs with a torn ACL often experience significant pain, especially when pressure is applied to the knee joint. If your dog shows signs of discomfort when you touch their leg, especially around the knee area, it’s a clear indication that something is wrong. You may notice your dog flinching, whining, or pulling away when you try to examine the injured leg.
Pain may also cause your dog to avoid putting weight on the affected leg, leading them to favor the other leg. This can result in a noticeable limp or a reluctance to engage in normal activities like walking or climbing stairs.

5. Behavioral Changes
Dogs with torn ACLs often experience discomfort and pain that can lead to changes in behavior. A previously active dog may become more sedentary, spending a lot of time lying down or avoiding physical activities. Your dog may also become more irritable or withdrawn due to the pain.
In addition to behavioral changes, some dogs may lick or chew the affected leg in an attempt to soothe the discomfort. If you notice your dog excessively licking or biting at their hind leg, it could be a sign that they are trying to relieve the pain from the torn ACL.
6. Instability or “Wobbling” When Walking
A torn ACL can cause instability in the knee joint, making it difficult for your dog to walk properly. The instability may cause your dog to appear “wobbly” or unsteady when walking, especially on uneven surfaces. In some cases, the leg may give out completely, causing the dog to stumble or fall.
This wobbling is a direct result of the ligament not providing the proper support to the knee joint, leading to abnormal movement. If your dog’s gait appears off or they seem to struggle to keep their balance, this could indicate a torn ACL.
7. Difficulty With Stairs or Jumping
Another symptom of a torn ACL in dogs is difficulty with stairs or jumping. Since the ACL provides stability to the knee joint, a torn ligament can make climbing stairs, jumping, or even walking uphill challenging for your dog. They may avoid jumping on furniture or hesitate when faced with stairs or elevated areas.
If your dog suddenly avoids jumping or seems hesitant to go up or down stairs, this could be a sign that they are experiencing knee pain and instability due to an ACL injury. Dogs that are reluctant to jump or climb stairs may also show signs of discomfort or stiffness when attempting these activities.

8. Decreased Activity Levels
A torn ACL often leads to decreased activity levels due to pain and discomfort. Your dog may seem less eager to go for walks, play fetch, or engage in their usual exercise routine. As a result, they may spend more time resting and may even seem lethargic.
While some reduction in activity is normal if your dog is in pain, a noticeable drop in enthusiasm for activities they once enjoyed is a sign that something is wrong. If your dog’s energy level drops significantly, it’s important to have them evaluated by a veterinarian.
9. Shifting Weight to the Unaffected Leg
Dogs with torn ACLs often compensate for the pain and instability by shifting their weight to the unaffected leg. This change in posture can lead to limping or favoring the good leg, which can eventually result in muscle atrophy or stress on the healthy leg over time.
If you notice your dog putting more weight on one leg and barely using the other, this is a clear sign of a torn ACL. Continued imbalance can lead to additional complications, so it’s important to address the issue as soon as possible.
Conclusion
A torn ACL is a painful and often debilitating injury for dogs, but with early recognition of the symptoms, treatment can begin promptly. If your dog shows signs of limping, pain, swelling, or difficulty moving, it’s essential to consult a veterinarian for a diagnosis. The sooner you address the problem, the better the chances of a successful recovery and the reduction of long-term complications. Whether through rest, physical therapy, or surgery, proper treatment can help your dog regain mobility and lead a comfortable, active life once again.