Dog Cruciate Ligament (ACL) Injury: Limping, Knee Instability, and What Owners Should Ask Next
A rear-leg limp that worsens after play is a classic cruciate pattern—learn what rest can and cannot do while you seek diagnosis.
A torn or partially torn cranial cruciate ligament (often compared to the human ACL) is one of the most common causes of sudden or progressive hind-limb lameness in dogs. Owners notice a toe-touching limp, stiffness after rest, difficulty rising, or a sit that looks shifted off one hip. Some dogs improve briefly with rest, then limp again after a run in the park. Diagnosis belongs with a veterinarian; treatment ranges from structured medical management in select cases to surgical stabilisation such as TPLO or other techniques, depending on size, activity, and severity.
Key takeaways
- Sudden rear-leg limping after a twist or awkward landing is a classic presentation.
- Rest alone does not reliably heal a complete tear in active dogs.
- Weight control and controlled physiotherapy matter before and after any procedure.
How the injury shows up at home
In day-to-day practice notes, owners describe a dog that was fine at breakfast and three-legged lame after chasing a ball. Others report a subtle intermittent limp that becomes obvious on stairs. Swelling on the inside of the knee, reluctance to jump into the car, and muscle loss on the affected thigh over weeks are common observations. Both large and small breeds can be affected; some dogs eventually injure the other knee as well.
What not to do while waiting for an exam
- Do not force long walks “to keep them moving” through an unstable knee
- Avoid off-lead sprinting, rough play, and slippery floors
- Do not start human anti-inflammatories—toxicity risk is real
Short leash toilet breaks and confined rest are safer than weekend hikes. Pain scales and gait notes help the clinician; our limping guide covers broader severity checks.
Diagnostic and treatment conversations
Expect an orthopaedic exam, and often sedation radiographs to assess the knee and rule out other causes. Surgical options and timelines vary. Ask about expected recovery length, activity restriction weeks, physiotherapy, and realistic return to sport or off-lead running. Medical management may be discussed for partial tears or dogs that are poor anaesthetic candidates—this is individual, not a social-media protocol.
Home support themes
- Keep body weight lean—extra kilos load the knee
- Use rugs on tile and hardwood
- Follow the exact post-op confinement plan if surgery is chosen
- Plan mental enrichment that does not require running
Joint and mobility context also appears in hip dysplasia and senior mobility articles.
Preparing questions before an orthopaedic consult?
Our Diagnostics Support pathway helps you organise limp timelines, video clips of gait, and questions about imaging or surgery discussions.
Educational content only. This page does not diagnose disease or replace care from a licensed veterinarian. Seek in-person help for emergencies or worsening symptoms.