Introduction
Anterior cruciate ligament (ACL) injuries are a common cause of hind limb lameness in dogs. The ACL is one of the major ligaments that stabilizes the knee joint. ACL tears or ruptures in dogs can occur due to trauma, genetics, obesity, and other factors, with some breeds being predisposed. Studies show the prevalence of ACL injuries in dogs ranges from 0.2% to 3.5%, with around 2610 ACL injuries per 100,000 dogs annually [1,2]. ACL tears are painful and debilitating for dogs, severely impacting their mobility and quality of life. Most ACL tears in dogs require surgical repair followed by substantial at-home care and rehabilitation for the dog to regain normal function of their hind limbs.
Causes and Risk Factors
The most common cause of ACL injuries in dogs is excessive twisting or turning of the knee joint. Certain activities like jumping, running, cutting, and pivoting can put high stress on the ACL and cause it to tear over time. Dogs that are very active and energetic are at higher risk.
Anatomy also plays a role. Dogs with long legs and narrow hocks, like Labradors and Greyhounds, are predisposed to ACL tears. The steep angle of their legs and minimal muscle mass causes their knee joints to be less stable. Small dogs like Yorkshire Terriers are also at higher risk due to the shallow trochlear groove in their knee caps. Breeds with hyperextensible hocks like German Shepherds are also more prone to ACL tears (source).
Obesity is another major risk factor, as excess body weight puts more strain on the ACL. Older, less active dogs are also at greater risk due to weakened tendons and ligaments from aging.
Symptoms
The most common symptom of an ACL injury in dogs is limping or lameness in the affected hind leg. Dogs will often avoid bearing weight on the injured leg by holding it up when standing or sitting. You may notice your dog suddenly yelp or cry out after a hard landing or quick change in direction, indicating the ACL tear occurred at that moment.
Dogs with a partial or complete ACL tear will have difficulty standing up on their hind legs. The knee joint feels unstable, causing the dog’s hind leg to buckle or give out when they try to put weight on it. Your dog may appear hesitant to run, jump up, or climb stairs, which puts strain on the injured knee.
Swelling and stiffness around the knee joint is also common after an ACL injury. Your dog may show signs of pain like whimpering, licking the knee area excessively, or snapping if you touch their leg. The symptoms usually start suddenly after a specific incident of playing or exercise. Left untreated, the lameness will persist and likely worsen over time as arthritis sets in. For more information, see this article on signs of ACL injury in dogs from Cortaro Farms Pet Hospital: https://www.cortarofarmspethospital.com/site/blog/2023/07/17/dog-acl
Diagnosis
To diagnose an ACL tear in dogs, veterinarians will perform a thorough physical exam and may order imaging tests like x-rays or MRI. Some of the key aspects of diagnosing ACL tears include:
Veterinary Exam – The vet will manipulate the knee joint and look for signs of instability, pain, or swelling. They may perform a “drawer sign” test where they try to slide the tibia forward while feeling for laxity in the joint.
X-Rays – These can help rule out bone fractures and identify any arthritis present. However, x-rays may not directly visualize a partial or complete ACL tear.
MRI – This imaging modality provides a detailed view of the soft tissues in the knee. An MRI can directly visualize a torn or ruptured ACL and help determine the extent of injury.
There are other specialized tests like tibial thrust tests that vets can use to diagnosis ACL tears as well. But the combination of a thorough physical exam and imaging like x-rays or MRI are often needed for an accurate diagnosis.
Surgical Treatment
The most common surgical treatments for ACL tears in dogs are TPLO (tibial plateau leveling osteotomy), TTA (tibial tuberosity advancement), and tightrope procedures. The type of surgery recommended often depends on the size of the dog, degree of injury, and surgeon preference. According to ACL SURGERY FOR DOGS:
TPLO involves cutting and rotating the top of the tibia to change the angle of the tibial plateau, stabilizing the stifle joint. This procedure is ideal for large, active dogs. Recovery time is around 8 weeks with strict exercise restriction.
TTA moves the tibial tuberosity forward to reduce stress on the ACL. It has a high success rate and is often recommended for small dogs. The typical recovery time is 6-8 weeks.
Tightrope procedures use a flexible wire anchored between the femur and tibia to stabilize the joint instead of replacing the torn ACL. This minimally invasive technique has a shorter recovery time of 6-8 weeks but may have a higher failure rate. According to ACL Surgery for Dogs – Cruciate Surgery | Leighton Vets, tightrope surgery has become a popular choice for ACL repairs in dogs.
Recovery Overview
The recovery process after ACL surgery in dogs is long and requires weeks of restricted activity. According to “Dog Torn ACL Surgery Recovery: An At-Home Aftercare Guide” (https://chasingtails.store/blogs/tips/dog-acl-surgery-recovery), the recovery timeline after ACL surgery typically lasts 6-8 weeks but can take up to 12 weeks depending on the size and age of the dog. The first 2 weeks after surgery focus on strict rest and confinement to allow initial healing. Weeks 3-6 involve gradually increasing activity and physical therapy exercises. Week 7 often marks the return to normal activity levels, but dogs should avoid running, jumping, or rough play until at least 8 weeks post-op. Complete recovery takes about 3 months, as the new ACL ligament continues maturing and strengthening over this time.
At-Home Care
After surgery, your dog will need attentive at-home care as they recover from ACL surgery. This involves managing their medication, using ice/heat therapy, restricting exercise, and beginning physical therapy exercises.
Medications
Your vet will prescribe pain medications and anti-inflammatories to manage your dog’s pain after surgery. It’s important to give these medications as directed to keep your dog comfortable. You may need to use a cone collar to prevent them from licking surgery site and interfering with the incision.
Ice/Heat Therapy
Applying ice packs wrapped in a towel to the surgery site can help reduce pain and swelling in the initial days after surgery. After the first week, your vet may recommend switching to gentle heat therapy instead. Always monitor your dog’s tolerance when using ice/heat.
Exercise Restriction
Your dog will need to avoid strenuous activity and exercise while recovering from ACL surgery. This usually means keeping them leash walked for potty breaks only for the first 2 weeks. Jumping, running, and playing should be avoided during the recovery period.
Physical Therapy
Early physical therapy is an important part of ACL recovery. Your vet will demonstrate exercises like passive range of motion to help maintain flexibility in the affected leg. Restricted activity should gradually increase over 8-12 weeks under your vet’s supervision.
Physical Therapy
Physical therapy is a critical component of recovery after ACL surgery in dogs. It helps restore range of motion, rebuild muscle strength, and get the leg functioning properly again. Physical therapy often begins 2-4 weeks after surgery and continues for 4-6 months.
Some of the key physical therapy techniques for dogs after ACL surgery include:
- Range of motion exercises – Gentle movements like passive flexion/extension of the knee joint and circular motions of the ankle. Studies show that consistent and gradual joint motion helps prevent post-operative cartilage damage and scar tissue build up [1].
- Strengthening exercises – Targeted exercises to rebuild muscle strength in the affected leg, such as standing on an unstable surface, cavalettis, or using resistance bands. Low-impact weightbearing exercise should begin about 6 weeks after surgery [2].
- Hydrotherapy – Water therapy using an underwater treadmill or swimming allows for building muscular strength with minimal weight bearing on the joints.
A rehabilitation program customized for the individual dog and their activity level is key for ensuring the best functional outcome after surgery. Consulting with a canine physical therapist can be extremely beneficial.
Potential Complications
Like any major surgery, ACL repair surgery in dogs carries some risks of complications. Some of the most common potential complications include infection, re-injury or re-tear of the ACL, and progression of arthritis, according to sources.
Infection is one of the top concerns after ACL surgery. The incision site provides an entry point for bacteria, and dogs have a tendency to lick the wound, further increasing infection risk. Signs of infection include redness, swelling, discharge, and fever. Infection requires rapid veterinary treatment with antibiotics and wound care. Preventive measures include the use of antimicrobial surgical scrub, antibiotics, and an Elizabethan collar to deter licking.
Re-tear of the repaired ACL is another complication, which occurs in around 10-15% of cases. Factors that can lead to re-injury include returning to activity too soon, failure of the graft or implants, or progression of arthritis. Re-tear usually requires a second surgery. Following post-op guidelines closely helps reduce re-injury risk.
Arthritis is a frequent consequence of ACL injury, as unstable knee joints lead to cartilage damage over time. While surgery helps stabilize the joint, arthritis may still worsen. Managing weight, controlled exercise, joint supplements, anti-inflammatories, and physical therapy can help control arthritis pain and progression.
Long-Term Outlook
Most dogs recover well after ACL surgery and physical therapy, with studies showing good long-term outcomes. In one study of 58 dogs after ACL repair, over 80% had minimal or no lameness at an average of 50 months after surgery (https://pubmed.ncbi.nlm.nih.gov/11058021/). Another study found that 32 out of 39 dogs had a satisfactory functional outcome 2-5 years after surgery (https://bmcvetres.biomedcentral.com/articles/10.1186/s12917-014-0266-8).
However, ACL surgery is not a cure. Ongoing management is required to maintain joint health and prevent re-injury. Weight management, activity modification, supplements, and medications may be part of a dog’s treatment plan. With proper care, dogs can return to normal activities and lead full lives after ACL repair. But the operated knee remains vulnerable and dogs may develop arthritis over time. Close communication with your veterinarian can help optimize your dog’s long-term outlook.