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Knee buckling is when one or both knees feel weak and give out. It can be accompanied by pain, but not always. If it happens a lot, it could be a sign of an underlying medical problem.

Knee buckling is also referred to as knee instability or weak knees.

Frequent knee buckling also raises your risk of falling and seriously injuring yourself, so it’s important to figure out the underlying cause. Keep reading to learn more about the causes of knee buckling and how to treat them.

Many cases of knee instability are caused by injuries, either from high-impact activities, such as running, or an accident. Common knee injuries include:

  • ACL tears
  • meniscus tears
  • loose bodies (pieces of bone or cartilage floating within the knee)

In addition to instability, knee injuries often cause pain and swelling in the affected knee.

Injury-related knee buckling usually goes away after you treat the underlying injury. Depending on the type of injury, you may need to do physical therapy or have surgery. While you recover, try to avoid putting pressure on your knee whenever possible.

The femoral nerve is one of two major nerves in your lower leg. Femoral neuropathy, which refers to dysfunction of your femoral neve, can cause weakness in your knees, making them more prone to buckling. Other symptoms of femoral nerve neuropathy include:

  • pain
  • tingling
  • burning
  • numbness in parts of your thigh or lower leg

Many things can cause femoral neuropathy, including:

Treating femoral neuropathy depends on the cause, but it usually involves surgery, pain medication, or lifestyle changes. In many cases, neuropathy isn’t curable, but treatment can help to reduce your symptoms or prevent them from getting worse.

Plica syndrome is caused by inflammation of the medial plica, which is a fold in the middle of the membrane that covers your knee joint. In addition to knee buckling, plica syndrome can also cause:

  • clicking sounds in your knee
  • pain on the inside of your knee
  • pain and tenderness in your kneecap

Most cases of plica syndrome are caused by a knee injury or overusing your knee. Treatment usually involves physical therapy to strengthen the muscles surrounding your knee. You may also need a corticosteroid injection to reduce inflammation. In rare cases, your doctor might suggest surgery to remove or adjust your plica.

Arthritis refers to inflammation in your joints, and it often affects your knees. There are many types of arthritis, but knee buckling is a common symptom of both osteoarthritis and rheumatoid arthritis, which is an autoimmune disease. While rheumatoid arthritis usually affects both knees, you may only have osteoarthritis in one knee.

Both osteoarthritis and rheumatoid arthritis can also cause:

  • pain
  • stiffness
  • a locking or sticking sensation
  • a grinding or clicking noise

While there’s no cure for arthritis, several things can help you manage your symptoms, including:

Some people with multiple sclerosis (MS) report having knee buckling as a symptom. MS is a condition that causes your immune system to attack the protective covering of your nerves. While there hasn’t been much research into the relationship between knee buckling and multiple sclerosis, weakness and numbness in your legs are common symptoms of MS. This may make it feel like your knee is buckling.

MS can cause a variety of symptoms that differ from person to person, but other common symptoms include:

  • vision loss
  • fatigue
  • dizziness
  • tremors

There’s no cure for MS, but corticosteroid injections can help to reduce nerve inflammation in your legs. Taking muscle relaxants can also help if you have stiffness or frequent spasms in your legs.

Frequent knee buckling may be a sign of an underlying injury or condition, so it’s a good idea to follow up with your doctor. In the meantime, try to rest your knee and apply either a hot or cold compress. You can also wear a knee brace or use a cane to reduce your risk of falling when your knees buckle.

You can also try these leg exercises for weak knees.

Knee buckling can range from a mild annoyance to a serious health hazard. Depending on what’s causing it, you may need physical therapy or surgery. Work with your doctor to figure out what’s causing your knees to buckle and use extra caution when walking up or down stairs.