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.
Here are a few potential causes for leg weakness resulting in sudden buckling and possible falls.
When a nerve root (part of a spinal nerve as it exits the spine) between L1 to S3 in your lower back is compressed, you may experience radiculopathy symptoms in your leg. The most common type of radiculopathy involves the sciatic nerve (formed by the L4-S1 nerve roots) and is called sciatica.1 Sciatica is typically felt as shooting pain that starts in the back and radiates through the back of the leg into the foot.
Other radiculopathy symptoms can include leg weakness, heaviness, and/or loss of function. Radiculopathy typically affects one leg at a time. You may also feel pain, numbness, and/or tingling in the affected leg.2 Higher nerve root compression (L1-L3) can affect the front of the thigh and groin region.
Radiculopathy usually occurs as a result of nerve root compression from a herniated disc, spinal stenosis (narrowing of the bony openings for nerve roots), spondylolisthesis (a vertebral body slipping forward on another), or other degeneration in the lumbar spine. The sciatic nerve controls the movement of the muscles in the thigh, calf, leg, and foot and is the most common source of radiculopathy.2
Depending on the severity of radiculopathy, your leg weakness may range from:
- Difficulty in lifting the foot
- Difficulty in lifting the entire leg
- Loss of balance while walking or an unstable gait
Radiculopathy usually resolves with nonsurgical treatments, including physical therapy, regular exercise, heat and cold therapy, and/or medication. Rarely, surgery may be required if a nerve root is severely compressed and/or the leg weakness persists and/or progresses.2
Central canal stenosis
Narrowing of the spinal canal is called central canal stenosis. Your spinal canal houses the spinal cord. Central canal stenosis can cause compression of the spinal cord and reduction in its blood supply. Narrowing of this canal can occur in the neck, upper back, and/or lower back.3 The spinal cord ends at L1 in adults. Stenosis below this level is not from cord compression but compression of nerve roots.
Read more: What Is Spinal Stenosis?
Central canal stenosis may occur due to severe disc herniation, abnormally overgrown bone (bone spurs), or thickening of the spinal ligaments.3 Other causes include trauma (bleeds) and tumors which grow into the spine.
You may experience3:
- Weakness in both legs
- Difficulty in walking
- Loss of balance
- Pain after walking variable distances (neurogenic claudication)
Central canal stenosis may be treated nonsurgically or surgically depending on its severity. If the spinal cord compression is severe (more than 30%) with marked leg weakness, surgery may be indicated.3
Diabetes mellitus can cause damage to the nerves and muscles in your legs and feet. These nerves typically receive lesser blood supply in diabetes, damaging their structure. The strength and thickness of the muscles are also significantly reduced in diabetic neuropathy, leading to leg weakness.4
A few common symptoms include4:
- Weakness in the leg and ankle
- Loss of balance and unsteady gait
- Aching, burning, or sharp pain in the leg
- Numbness or complete loss of sensation in the leg and feet, typically affecting the areas covered by a stocking (in the hands, the areas covered by a glove may be affected)
Foot symptoms in diabetic neuropathy are usually managed with medications, special shoe inserts, and/or special type of footwear.
Cauda equina syndrome
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
- Numbness in the groin, buttocks, genitals and/or inner thighs (saddle numbness)5
- The inability to control your bowel and/or bladder movements5
- An inability to pass urine, reduced urinary sensation, loss of desire to pass urine, or a poor stream6
If you experience any of these symptoms, consult your doctor immediately. Doctors advise treating this condition within 24 to 48 hours of symptom occurrence in order to preserve lower limb function.5,6,7
If you experience leg weakness and are unsure about the cause, consult your doctor. A doctor can conduct specific clinical and diagnostic tests to identify the underlying cause for your leg weakness and formulate an effective treatment plan.