What Are Common Causes of Left Leg Weakness?

Injuries may cause left leg weakness.
Intense exercising may cause left leg weakness.
Sciatica and other back problems may cause leg weakness on one side.
Article Details
  • Written By: N. Swensson
  • Edited By: Jenn Walker
  • Last Modified Date: 17 July 2014
  • Copyright Protected:
    Conjecture Corporation
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Weakness in the left leg can be caused by a number of underlying problems. The specific cause can very depending on a person's other symptoms and if he or she has any existing health conditions. Some causes of left leg weakness may indicate very serious medical conditions, such as a blood clot, stroke or a neurological problem. Some back and spine conditions, such as sciatica, can also result in weakness in the left leg. The condition also is commonly caused by injury, as can occur in many types of sports or even during intense exercise.

One condition that occurs more frequently in the left leg is deep vein thrombosis. This problem occurs when a blood clot forms in one of the veins of the leg. The condition is dangerous because the blood clot can travel through the vein to the lungs, causing a pulmonary embolism. This is a very serious problem which can be fatal, so prompt medical attention is very important.

Sciatica and other back problems that cause spinal compression are also a common cause of leg weakness on one side. The sciatic nerve runs from the lower back into each leg. When the nerve becomes irritated due to a spinal problem, it can result in pain and weakness. Other symptoms of sciatica include pain and difficulty standing, sitting, or walking. Depending on the cause of sciatica, it may go away on its own. In other cases, physical therapy, medication, or surgery may be needed.


Another health problem that may cause left leg weakness is stroke. As with sciatica, the weakness can occur on the right or left, but is usually only on just one side of the body. If the stroke affects the right side of the brain, the weakness will occur in the left side. Weakness from a stroke can be felt in any part of the body, including the legs. A stroke happens when blood flow to the brain is interrupted. This can result in permanent physical damage. Prompt medical care is important if a stroke is suspected, as it can help minimize permanent disability.

Left leg weakness can also be caused by an injury to the area. Muscle injuries due to playing sports or exercising can make walking and standing difficult. This type of weakness, however, will generally improve over time, unlike the weakness associated with a stroke or other neurological problem. Left leg weakness caused by these conditions usually stays the same for a long period of time or gradually worsens over time.


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Post 3

My child presented with this problem yesterday. He is 3 and a half years and continued falling. He even could not climb the stairs. He claimed he has no pain but we noticed the lack of strength. He does not have any other symptoms, injuries or health background. I'm taking him to the doctor but I want to know if it can be serious.

Post 2

My left leg remained weak for months after my wreck. I had been sitting in the back seat without a seatbelt when someone pulled out in front of us. My dad swerved, but he could not miss the van that just kept coming.

When he first hit the van with the front of the car, I thought we were dead. Once I realized we were okay, I tried to get out of the car. I took one step and fell down in pain. I could not stand up!

My left knee had rammed super hard into the back of the driver’s seat. The doctor originally thought I might need surgery, but it started to heal on its own after a few weeks. I could not fully step down and stand on that foot for months, though.

Post 1

My sister’s left leg became very weak after she developed sciatica. The pain would shoot down her spine and through her leg. She said that it felt tingly, almost like it was going to go numb, but it would be in pain also.

She had some difficulty walking during flare-ups of sciatica. She had to hobble about and limp. It was weird to her that just one leg was affected.

Her doctor told her some exercises she could do that might prevent the symptoms. However, while she is in the middle of an episode, she can’t do these exercises, because her left leg is too weak.

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