SYMPTOM
Knuckling
Owners may observe knuckling in their pet, which can present in various ways depending on the underlying cause.
Neurological
Conditions affecting the spinal cord, peripheral nerves, or brain can disrupt the signals that coordinate paw placement. This may involve compression, inflammation, or degenerative changes in nervous tissue that alter proprioception—the animal's sense of where its limbs are in space.
Musculoskeletal
Pain or structural changes in joints, tendons, or muscles can lead to altered weight distribution and paw placement. When bearing weight becomes uncomfortable, an animal may shift posture in ways that present as knuckling.
Orthopaedic
Developmental or acquired bone and joint abnormalities, particularly in the carpus or digits, can affect the mechanics of how the paw contacts the ground. Laxity in supporting structures may also allow the paw to fold under during movement.
Metabolic or Systemic
Certain metabolic disturbances or systemic illnesses can influence nerve function or muscle strength over time. These processes may contribute to coordination changes that become visible as knuckling.
Vascular
Disruption to blood flow, whether sudden or gradual, can compromise nerve or muscle function in the affected limb. This may result from clot formation or other circulatory changes that alter tissue oxygen delivery.
Toxic or Nutritional
Exposure to certain substances or prolonged nutritional imbalances can affect peripheral nerve health. The pattern often involves gradual onset and may affect multiple limbs as the underlying process progresses.
Why timing matters
Early observation
When knuckling first appears, the pattern of onset offers clues about what might be happening. A sudden appearance in a previously normal animal suggests a discrete event—perhaps trauma, a vascular incident, or acute nerve compression. Gradual onset over days to weeks may point toward progressive processes such as inflammation, degenerative change, or metabolic influence. The initial context—whether during rest, activity, or particular movements—can also help characterise the nature of the change.
Later presentation
If knuckling persists or recurs, the evolution of the picture becomes informative. Worsening over time may suggest progression of an underlying process, while stable knuckling that does not change may reflect a static injury or adaptation. Intermittent knuckling that comes and goes can indicate fluctuating factors such as fatigue, pain levels, or inflammation. The response to rest, activity, or environmental temperature may also become clearer with observation over weeks.
Patterns of progression vary widely depending on the underlying cause. Some conditions remain stable once established, while others worsen steadily or in stepwise fashion. In younger animals, developmental changes may alter the picture as growth continues. In older animals, degenerative processes may advance slowly, and the threshold at which knuckling becomes visible can shift with muscle condition, weight, or activity level. Individual variation means that timelines and trajectories differ, and isolated observation at a single point offers limited insight.
Conditions commonly associated
Degenerative Myelopathy
Loss of proprioception causes dogs to stand on the tops of their paws rather than the pads.
Degenerative Myelopathy in Dogs
Degenerative myelopathy can cause knuckling as the progressive degeneration of spinal cord white matter disrupts the nerve signals that coordinate paw placement, often beginning with subtle dragging or folding of the toes in one or both hind limbs. This typically appears in older dogs and worsens gradually over months.
Intervertebral Disc Disease in Dogs
Knuckling may occur when intervertebral disc material compresses the spinal cord or nerves, interrupting the sensory feedback that tells the brain where the paw is in space. The degree of knuckling often reflects the severity and location of the compression.
Fibrocartilaginous Embolism (FCE)
A fibrocartilaginous embolism can produce sudden knuckling when the blocked blood vessel supplies a section of spinal cord responsible for hindlimb coordination, resulting in an abrupt loss of proprioception on the affected side. This typically presents without obvious pain, distinguishing it from some other spinal causes.
Osteosarcoma
Osteosarcoma affecting a limb bone can lead to knuckling when pain or structural instability alters weight-bearing mechanics, causing the dog to place the paw abnormally or avoid fully extending the affected leg. This may be seen alongside progressive lameness and swelling near the tumour site.
When to explore further
If knuckling persists beyond a few days without improvement, particularly if it appeared suddenly in a previously normal limb.
If the pattern progresses to involve additional limbs, or if the degree of knuckling worsens over time despite no obvious change in activity or environment.
If knuckling is accompanied by other changes such as altered gait, reluctance to bear weight, changes in muscle bulk, or visible discomfort during movement.
If the animal shows difficulty rising, navigating stairs, or performing movements that were previously routine, suggesting that the underlying process is affecting function more broadly.
If there is a known history of trauma, recent illness, or exposure to unfamiliar substances that might offer context for the timing of onset.
Knuckling gains meaning when considered alongside the animal's history, the pattern of onset, and any accompanying changes in movement or behaviour. Observing how the picture evolves over days to weeks can help clarify whether the process is static, progressive, or intermittent. These observations, when shared with someone familiar with the individual animal's medical context, can inform decisions about whether further evaluation might be useful and what form that might take.
Last reviewed: 24 April 2026 · Dr Alastair Greenway MRCVS