A buckled leg is often caused by temporary muscle fatigue, poor neuromuscular control (brain-to-muscle signal delay), or underlying joint issues like arthritis, meniscus tears, ligament damage (ACL/MCL), nerve problems (pinched nerve), weak hip/quad muscles, patellar instability, or hypermobility syndromes, making the knee unstable and suddenly unable to support weight, leading to a fall.
Simple, gentle exercises like knee extensions, heel and toe raises, straight leg lifts, and supine hamstring curls can make a real difference. These movements target the muscles that support your knees, your quadriceps, hamstrings, calves, and hips.
Weakness in the leg can arise from three principal causes: nerve problems, muscle weakness, and SI joint dysfunction. Treatment is best directed at the underlying problem. Lumbar disc disorders such as protrusion and herniations can compress the spinal nerve thereby compromising the nerve signal to the muscle.
Causes of nerve damage include direct injury, tumor growth on the spine, prolonged pressure on the spine, and diabetes. A spinal cord injury. Spinal cord injuries are among the most common reasons that legs give out. These injuries vary in severity but should always be evaluated immediately by a spine specialist.
The sciatic nerve gives nerve impulses to the leg and foot muscles. Compression of this nerve can cause weakness in the leg muscles, particularly at the knee or ankle. This muscle weakness may cause difficulty moving the leg or foot and a tendency for the knee or ankle to buckle.
A feeling of sudden leg weakness, causing your legs to give out or buckle can be alarming. Weakness in your leg(s) may occur from problems in the nerves and/or muscles in your lower body and is usually treatable. Rarely, the underlying cause may be a serious medical condition requiring immediate medical attention.
Lifestyle and home remedies
Cauda equina syndrome is a rare, but serious medical condition. This syndrome occurs when the lower part of the spinal cord (cauda equina) is compressed due to tumors, collection of fluid (abscess), or severe disc herniation. Cauda equina syndrome may cause: Sudden, severe weakness in both legs5.
Sciatica red flags signaling a medical emergency include loss of bladder/bowel control (urinary retention, incontinence, inability to pass stool), saddle anesthesia (numbness in the groin/genitals/inner thighs), progressive weakness, severe pain at rest/night, or symptoms after significant trauma, potentially indicating conditions like cauda equina syndrome, fracture, or infection. These symptoms require immediate medical evaluation.
As the lumbar spinal canal shrinks, the nerves that go through it are squeezed. This squeezing may cause back pain, leg pain and leg weakness. Many adults have this kind of stenosis.
MS Symptoms in Legs
The top symptoms in the legs include: Weakness: Legs may feel heavy, fatigued, or harder to move, especially after walking or standing for long periods. Numbness or Tingling: A “pins and needles” sensation, or complete numbness, often starting in the feet and moving upward.
If you have nerve damage in your knees, such as that caused by diabetic neuropathy or multiple sclerosis, it can lead to knee buckling.
Leg pain can signal various diseases, often related to poor blood flow (like Peripheral Artery Disease (PAD) or Deep Vein Thrombosis (DVT)), nerve issues (like Sciatica, Diabetic Neuropathy, or Restless Legs Syndrome), joint/bone problems (like Arthritis or infections), or muscle conditions, with symptoms varying from exercise-induced cramping to persistent aching, swelling, or numbness.
The #1 mistake making bad knees worse is excessive rest or inactivity, which weakens supporting muscles, leading to stiffness and instability, creating a vicious cycle of pain and dysfunction, even though it feels counterintuitive; the solution involves controlled movement and strengthening exercises (like walking, swimming) to support the joint. Other major mistakes include wearing unsupportive shoes, carrying excess weight, and performing movements that involve twisting.
Your knees may be most painful when you walk, particularly when walking up or down hills or stairs. Sometimes, your knees may "give way" beneath you or make it difficult to straighten your legs. You may also hear a soft, grating sound when you move the affected joint.
However, vitamin deficiencies in B12, D, and magnesium play a key role in sciatic pain and relief. If you've tried stretches, painkillers, or even therapy and found little to no relief, this could be your answer. A B12 vitamin deficiency, for example, leads to increased nerve pain and sciatica symptoms.
Below are some examples of conditions often mistaken for sciatica:
Best sleep positions for sciatica
Legs can “give way” due to muscle issues, especially while exercising. These instances are not cause for alarm typically. But if your legs give way and you lose complete control or feeling, the spinal nerves are likely the culprit. The nerves in our spine help deliver signals from our brain to the legs.
Symptoms of a blocked artery in the leg, often Peripheral Artery Disease (PAD), typically start as muscle pain, cramping, or fatigue in the calves, thighs, or hips during activity (like walking) that goes away with rest, known as claudication. More severe blockage causes resting leg pain, cool skin, slow-healing sores, hair loss, shiny skin, or even gangrene, indicating significantly reduced blood flow.
Symptoms of Guillain-Barré syndrome
You might feel tingling, numbness or pins and needles in your feet and hands first. This is usually followed by muscle weakness and difficulty moving your joints. Other symptoms can include: sharp, shooting pain (nerve pain), often in your legs or back.
Nerve Damage and Loss of Sensation
Patients with severe sciatica often experience numbness and tingling in their legs and feet. In extreme cases, this nerve damage is lasting and can even lead to paralysis. You may also be experiencing nerve damage if you notice reduced reflexes or weakness in your legs.
If your sciatica doesn't resolve itself without treatment, here are seven ways to permanently cure sciatica.
11 Things to Avoid if You Have Sciatica