A limp that came on suddenly, get this examined

What this tends to look like

• Fine one minute, limping the next, often after a run, a jump, or an awkward landing
• Clearly one leg rather than general stiffness
• May hold the leg up, touch the toe down lightly, or shift weight off it when standing
• Sometimes a yelp at the moment it happened, sometimes nothing at all
• Can look better after rest and worse again after activity, which is misleading
• In larger dogs, often a hind leg, and often a knee

What is usually going on

Sudden lameness and gradual stiffness are two different problems that get treated as one because they both look like a dog moving badly. Gradual stiffness across several joints is usually arthritis. Sudden lameness in a single leg is usually a structural injury: a cruciate ligament tear, a torn muscle, a cracked toenail, a foreign body in a pad, a dislocating kneecap, or in an older large-breed dog occasionally a bone tumor. None of those are managed with a joint supplement, and one of them is a genuine emergency.

There is a specific trap here worth naming. A partial cruciate tear often improves with a week of rest, which reads as recovery, and then fails completely a month later because the joint was never stable. Roughly half of dogs that tear one cruciate go on to tear the other. Catching it early changes the options available and it changes the long-term outcome for that knee, and no amount of glucosamine substitutes for knowing whether the ligament is intact.

We are not offering remedies on this page. Arnica has a place after a known knock, and you will find it on our bruises page, but reaching for it before anyone has established what is damaged is the wrong order. An examination takes fifteen minutes. Get that first.

What you can do at home

• Strict rest starting now. Short leads for toileting only, no stairs, no jumping, no off-lead running
• Check the foot and the nails carefully before you assume it is a joint. Split nails and pad injuries are common and easy to miss
• Compare the leg with the other side for swelling, heat, or a joint that sits differently
• Do not give human painkillers. Ibuprofen and acetaminophen are toxic to dogs, and cats are far more sensitive again
• Note exactly what they were doing when it happened. That single detail often points at the diagnosis
• Film them walking away from you and back on a hard flat surface. It is genuinely useful in the consulting room

What progress should look like

How long to give this before you conclude it is not working.

• Today or tomorrowGet examined. Sudden single-leg lameness is the case for seeing someone rather than waiting.
• First 48 hoursStrict rest regardless. If it is soft tissue, rest is the treatment. If it is structural, rest prevents it worsening.
• One to two weeksA simple strain should be steadily improving. Improvement that stalls or reverses points at something structural.
• If it seems better in a weekStill get it checked before returning to normal exercise. Apparent recovery is the classic partial cruciate pattern.

When to stop and call your vet

• No weight on the leg at all, or a limb at an unnatural angle
• A joint that is hot, swollen, or larger than its pair
• Pain that is getting worse rather than better on rest
• Any limp in an older large-breed dog that persists beyond a couple of weeks, which needs an X-ray