SYMPTOM
Hind leg weakness
Reduced strength or stability in the back legs, visible as wobbling, knuckling, or difficulty supporting weight.
Neurological: Spinal
Conditions affecting the thoracolumbar or lumbosacral spinal cord can interrupt the nerve signals controlling hind limb movement and strength. Intervertebral disc disease, degenerative myelopathy, spinal stenosis, and fibrocartilaginous embolism can all produce varying degrees of hind leg weakness. The pattern of weakness (whether it affects one limb or both, whether it is symmetrical, and whether proprioceptive deficits accompany the motor weakness) can help localise the level and nature of the spinal involvement.
Musculoskeletal
Pain and mechanical dysfunction in the hips, stifles, hocks, or lumbosacral junction can produce apparent weakness in the hind limbs. Bilateral hip dysplasia, cruciate ligament disease, or lumbosacral disease may all limit the animal's ability to generate normal propulsive force with the hind legs. The weakness in these cases may be more accurately described as reluctance to load or use the limbs normally due to discomfort, and the animal may still have normal neurological function despite appearing weak.
Neuromuscular
Conditions affecting the peripheral nerves, neuromuscular junction, or muscles themselves can produce hind limb weakness through different mechanisms than spinal cord disease. Peripheral neuropathies may produce weakness with or without sensory changes. Myasthenia gravis can cause fatigable weakness that worsens with sustained activity. Inflammatory myopathies may affect the large muscle groups of the hind limbs, reducing their ability to generate force during locomotion.
Metabolic or Endocrine
Systemic metabolic derangements can affect muscle function and nerve conduction in ways that produce hind leg weakness. Severe electrolyte imbalances, particularly hypokalaemia, can cause generalised muscle weakness, which in cats can show as a plantigrade stance of the hind limbs, difficulty jumping and a drooping neck. Hypothyroidism may produce a combination of peripheral neuropathy and myopathy. Diabetic neuropathy in cats characteristically produces hind limb weakness with a plantigrade stance.
Degenerative
Progressive degenerative conditions of the spinal cord, particularly degenerative myelopathy, produce gradually worsening hind leg weakness over months. The condition typically begins with subtle incoordination and mild weakness that progresses to more obvious difficulty walking, eventual dragging of the hind feet, and ultimately loss of hind limb function. The progressive nature of the decline, which is often uneven between the two hind legs in the early stages, combined with an absence of pain, characterises this degenerative process.
Why timing matters
Early observation
Early hind leg weakness may manifest as subtle changes that are easily attributed to other causes. The animal may occasionally stumble on slippery surfaces, take slightly wider turns, or show a barely perceptible wobble in the hind end during walking. Nail scuffing on the tops of the hind paws may develop before obvious gait changes are apparent, leaving visible wear marks on the dorsal surface of the nails. At this stage, the changes may be intermittent (more noticeable when the animal is tired, after prolonged rest, or on certain surfaces) and may be dismissed as clumsiness or the effects of ageing.
Later presentation
As hind leg weakness progresses, the functional impact becomes more apparent. The animal may cross its hind legs when walking, swing the hind end excessively, struggle on stairs, slip on smooth floors, or have difficulty rising from a lying position. Muscle atrophy in the hind limbs may become visible, producing a contrast between well-muscled forequarters and thinner hindquarters. At more advanced stages, the animal may drag one or both hind feet, require support to walk, or collapse in the hind end during activity. The transition from subtle gait changes to functional impairment often occurs gradually but may feel sudden to the owner when a threshold of compensatory ability is crossed, which is distinct from weakness that truly appears over minutes to hours.
The rate of progression provides important context about the nature of the underlying condition. Degenerative myelopathy typically progresses slowly over many months, while disc-related compression may worsen acutely or fluctuate. Metabolic causes may show rapid improvement with correction of the underlying imbalance. Neoplastic causes may build slowly or appear acutely. Musculoskeletal causes may fluctuate with activity levels and environmental conditions. Whether the weakness is progressing rapidly, slowly, or in a stable pattern helps characterise the type of process at work.
Conditions commonly associated
Degenerative Myelopathy in Dogs
Degenerative myelopathy causes gradual loss of the nerve fibres that carry signals to the hind limb muscles, so muscle strength and control decline progressively over time.
Intervertebral Disc Disease in Dogs
Compression of the spinal cord or nerve roots by displaced disc material reduces the nerve signal reaching the hind limb muscles, resulting in weakness that ranges from mild to pronounced depending on the degree of compression.
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Intervertebral Disc Disease (IVDD)
Spinal cord compression affecting thoracolumbar discs causes weakness in the hind limbs.
Laryngeal Paralysis
Progressive hind limb weakness develops in many dogs as part of the broader polyneuropathy (GOLPP).
Haemangiosarcoma
Anaemia and cardiovascular strain from bleeding make affected dogs weak and exercise-intolerant.
Syringomyelia
Neurological dysfunction from spinal cord damage can cause progressive limb weakness.
Cauda Equina Syndrome
Reduced nerve signal to the hind limbs from cauda equina compression can leave the back legs weak, particularly after exercise.
Lumbosacral Stenosis
Pressure on the nerves supplying the hind legs can leave them feeling weaker or less steady than usual.
Wobbler Syndrome (Cervical Spondylomyelopathy)
Compression of the spinal cord in the neck disrupts nerve signals travelling to the hind legs, leaving them weaker than normal.
Sarcopenia in Senior Dogs
Loss of muscle mass with age particularly affects the large hindlimb muscles, leaving them noticeably weaker.
Border Collie Collapse
After 5 to 15 minutes of strenuous exercise, affected dogs can develop a stiff, short-striding gait in the hind legs or in all four legs, scuff their feet and become wobbly, and some stagger and collapse. The abnormal gait lasts 5 to 30 minutes before full recovery.
Exercise-Induced Collapse
The hind limbs are typically affected first, becoming weak within minutes of intense exercise as this condition takes hold.
Hyperaldosteronism in Cats
Weakness through the back legs reflects the low blood potassium this condition produces, which impairs normal muscle function.
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Aortic Thromboembolism in Cats
A blood clot lodging in the artery that supplies the hind legs produces sudden weakness or paralysis of one or both hind legs in cats, with marked pain and cold limbs.
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Fibrocartilaginous Embolism (FCE)
Blockage of a spinal cord blood vessel by disc material causes hind leg weakness that begins abruptly, is often worse on one side, and rarely progresses past 12 hours.
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Acute Polyradiculoneuritis in Dogs
Inflammation of the nerve roots typically begins as a short-strided hind leg gait and progresses within 1 to 2 days to weakness of all four legs.
When to explore further
Hind leg weakness that is accompanied by knuckling of the paws (where the animal places the top of the foot on the ground rather than the paw pad) suggests impaired proprioception, the ability to sense limb position, which typically indicates neurological involvement rather than a purely musculoskeletal cause.
When weakness is clearly progressive over weeks, with a discernible trend of worsening function rather than a stable or fluctuating pattern, the trajectory itself becomes informative and may suggest an underlying process that is actively advancing.
Hind leg weakness that is notably asymmetric, affecting one side more than the other, may suggest a focal lesion affecting one side of the spinal cord or a unilateral peripheral nerve or musculoskeletal problem, rather than a symmetrical systemic process.
When hind leg weakness develops alongside changes in bladder or bowel control, the involvement of autonomic nerve function alongside motor function may indicate that a broader area of the nervous system is affected than motor pathways alone.
In cats, hind leg weakness accompanied by a plantigrade stance (walking on the hocks with the heel touching the ground) may suggest a specific pattern of peripheral nerve involvement that is associated with metabolic conditions, particularly those affecting glucose regulation.
Hind leg weakness that appears over minutes to hours, or that moves within a day or two from wobbliness to being unable to stand or walk, is a separate pattern from weakness that builds over weeks. In dogs, disc extrusion in short-legged (chondrodystrophic) breeds is often acute and severe, fibrocartilaginous embolism begins abruptly, often during running or jumping and usually without spinal pain, and acute polyradiculoneuritis moves from a short-strided hind leg gait to weakness of all four legs within 1 to 2 days. With disc extrusion, the outlook depends on whether deep pain sensation is still present. This is assessed in a neurological examination from the dog's behavioural response, such as a bark or a turn of the head, to a firm pinch of a toe, and cannot be judged from how the legs look or move at home. For small-breed dogs treated surgically for thoracolumbar disc extrusion, the MSD Veterinary Manual gives recovery rates of 85 to 95% when the dog cannot walk but deep pain sensation is intact, 50% when deep pain sensation has been lost for less than 24 hours, and under 50% when it has been lost for more than 24 hours.
In cats, weakness or paralysis of one or both hind legs that appears suddenly, together with marked pain, cold hind legs and paw pads that look pale or purple, is the pattern of aortic thromboembolism, in which a blood clot lodges in the artery supplying the hind legs. The MSD Veterinary Manual describes the pain as extreme at first, notes that the clot most commonly forms when the left atrium of the heart is enlarged by cardiomyopathy, and states that euthanasia is common.
Where hind leg weakness has come on gradually and is not changing from day to day, careful observation of its specific nature can provide useful characterisation. Noting whether the weakness appears worse after rest or after activity, whether it is symmetrical or favours one side, whether the animal seems aware of where its hind feet are positioned, and whether the weakness is steady or fluctuates throughout the day can build a detailed picture of the pattern. Watching the animal walk on different surfaces (carpet versus tile, level ground versus inclines) may reveal aspects of the weakness that are not apparent in one environment alone. Weakness that appears over minutes to hours is a different pattern, and is described among the considerations for exploring further.
Last reviewed: 9 October 2026 · Dr Alastair Greenway MRCVS