TL;DR: Patellar luxation is a common condition where a dog's kneecap slips out of position, often causing an intermittent "skipping" motion. While usually not an emergency, you should schedule a veterinary exam within 48 hours to manage discomfort and prevent long-term arthritis.
What is patellar luxation and why does my dog’s knee keep popping out of place?
- Patellar luxation occurs when the kneecap (patella), which normally sits in a groove at the end of the femur, slips out of its track.
- This can be caused by genetic factors, such as a shallow groove or malaligned limb, or can result from physical trauma.
- Dogs with this condition often "skip" or run on three legs for several steps until the kneecap snaps back into its proper position.
What is the urgency level for patellar luxation and when should I see a vet?
- A popping knee is generally considered a Medium urgency level; while rarely life-threatening, it is a progressive condition that leads to discomfort and osteoarthritis.
- You should schedule a veterinary exam within the next 24 to 48 hours to discuss long-term management.
- Seek immediate emergency care if your dog becomes suddenly non-weight-bearing, vocalizes in pain, or shows significant swelling in the limb.
How can a video of my dog's movement help with veterinary triage?
- A video is one of the most helpful tools because patellar luxation is often intermittent.
- Adrenaline or temporary realignment may cause your dog to walk normally once they arrive at the clinic, making diagnosis difficult.
- Capturing the "skipping" behavior on camera helps the veterinarian determine the frequency and severity of the episodes for accurate grading and treatment.
Clinical Context (Merck Veterinary Manual)
Patellar luxation in dogs involves displacement of the patella from the trochlear groove of the femur, detectable via stifle palpation. Clinical signs vary with severity. In Grade I, signs are mild and the patella readily returns after manual luxation. Grade II involves patellar luxation during joint flexion, resolving upon extension, causing a skipping lameness. Grade III presents with the patella more frequently dislocated and consistent lameness, often with evident bone deformities. Grade IV exhibits severe lameness and limb deformations. Radiography reveals limb changes correlating with the luxation grade. Medial patellar luxations are common in cats and small dog breeds, while lateral luxations are more frequent in large dogs. Surgical intervention depends on the severity and may include orthopedic and soft-tissue procedures, such as fascial releasing incisions, joint capsule and retinaculum imbrications. Patellar luxation can be associated with hindlimb deformities affecting the hip joint, femur, and tibia, including coxa vara, femoral bowing, tibial rotation, shallow trochlear groove, and femoral condyle hypoplasia.
Chapter: Orthopedics
Source: The Merck Veterinary Manual, 11th Edition (Page 1195)