One day, you and your pup might be in the backyard or at the park, running and playing, when your pup’s legs buckle beneath them. This situation can be extremely scary for both you and your pet, who might find themselves unable to walk! But regardless of whether your pup gets up and resumes playing or struggles to move, leg weakness is something you should take seriously.

A number of potential problems could be to blame for your dog’s hind legs giving out at random. Here are six possibilities.

1. Arthritis: Osteoarthritis, which causes inflamed and painful joints due to cartilage breakdown, can cause dogs young and old significant pain in their hips and legs. Due to ongoing pain, dogs might experience weakness in the front or back legs. This weakness can be worsened by muscular atrophy if your dog avoids movement. Over time, this could cause abnormal movement in the legs or even the legs giving out. Should they fall or collapse, your pup should still be able to move their legs and feet, although they may experience pain.
2. Hip dysplasia: Hip dysplasia is a skeletal condition that commonly affects large dog breeds. The condition leads to the deterioration of the hip joint, which can cause total hip dysfunction and hind leg weakness or collapse. Genetics are often to blame for hip dysplasia, as are malnutrition and excessive growth in large dogs. Dogs with this condition may experience stiffness in the hips and hind legs, an altered gait, reduced activity and pain.
3. Vertebral problems: Along your dog’s back, the spinal vertebrae protect the spinal cord and the nerves that branch out from it to other parts of the body. Degeneration of the vertebrae or the discs between them could compress the nerves leading to the legs, causing weakness or dysfunction. For example, herniated discs caused by degenerative disc disease are common causes of numbness, prickliness and weakness in a dog’s hind legs.
4. Nervous system problems: More severe damage to the nervous system might also interrupt the control your dog has over their front or hind legs. Trauma or certain diseases can result in nerve damage. One disease called canine degenerative myelopathy attacks the sheath that protects the spinal cord’s nerve cells slowly. Over time, dogs with this condition often experience hind leg tremors and weakness and trouble walking or standing. This disease is unlikely to cause pain.
5. Spinal cord injury: If your dog has suffered a traumatic injury, such as being hit by a car, they may have sustained damage to their spinal cord. This type of damage could fully or partially paralyze your pup, rendering them unable to stand or walk.
6. Slips and trips: It’s possible that your dog’s legs have given out temporarily because they simply slipped or had momentary weakness after turning in a strange way. If your pup lost their footing but was able to get back up and walk around normally, there’s probably nothing major to worry about. Monitor them for a while after to make sure they don’t appear to be in pain or develop a limp or strange gait.

If you notice hind leg weakness or collapse in your pup, take note of what was happening just before the collapse, whether or not your dog experienced any mobility changes before or after and how quickly your dog returned to normal, if they were able to get back up. These bits of information may help your vet narrow down the problem at hand and treat your dog as soon as possible.

A trip to the emergency vet is warranted if your pup cannot walk or stand at all after collapsing, or if they are moving strangely and appear to be in pain. Your vet will likely need to run a number of tests—ranging from physical examinations and mobility tests to X-rays and blood tests—to identify the source of the problem. Diagnostic imaging is typically necessary to discern whether the problem is related to the nervous system, skeletal system, muscular system or something else entirely. With an accurate diagnosis at hand, your vet can advise you on the best way to treat your pup’s condition.

Unfortunately, every underlying problem will have a different treatment and prognosis. Things like arthritis can usually be managed well with joint supplements and physical therapy, but more serious diseases might not have an effective long-term treatment or cure.

Paying attention to your dog’s mobility problems and other symptoms will ensure you get them the help they need right away so their pain and mobility don’t worsen. Help your furry friend stay active and safe by keeping a close eye on their legs.