Knee Buckling

Medically Reviewed By William C. Lloyd III, MD, FACS
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What is knee buckling?

Knee buckling is the sensation of the knee giving out or giving way. It can seem like the knee will collapse if you put all your weight on it. The knee can feel like it is bending the wrong way, twisting, or moving from side to side when it shouldn’t. The name for this symptom is knee instability or unstable knee.

The knee is the largest joint in the body. It’s also one of the most complex joints, which makes it easy to injure. It consists of four bones—the thigh bone (femur), kneecap (patella), shin bone (tibia), and lower leg bone (fibula). Cartilage, synovial fluid, and other tissues cushion and protect the bones.

Four very strong ligaments stabilize the four bones that make up the joint. Two collateral ligaments are on the sides of the knee—the medial one is on the inside and the lateral is on the outside. They control and limit sideways movements. There are also two cruciate ligaments that cross each other in an “X” inside the knee joint—the anterior one is in the front and the posterior one is in the back. They regulate back and forth movements.

Diseases or injuries to any of the bones, ligaments, or other joint components can result in knee instability. Knee buckling can also occur when the muscles that support the knee are weak or injured. However, many times there is no clear reason for the sensation of knee buckling.

Knee buckling is a fairly common symptom, affecting about 10% of U.S. adults. Most people who have it report recurrent episodes. Knee buckling when walking, climbing stairs, and twisting or turning is most common. Having knee instability increases the risk of falls and serious injuries, especially in older adults. So, it’s important to see your doctor if your knee feels weak or unstable. Seek immediate medical care for any injury involving the knee.

What other symptoms might occur with knee buckling?

If you have knee buckling with any other symptoms, see your doctor promptly. An unstable knee puts you at risk of falling and can be a sign of an injury or a potentially serious condition. Seek immediate medical care (call 911 for assistance if you can’t walk or drive) if you have any injury that involves the knee.

Most symptoms that occur with knee buckling affect the knee joint or supporting muscles. Depending on the underlying cause, other types of symptoms are possible.

Joint-related symptoms that may occur along with knee buckling

When knee buckling is the result of diseases and injuries of the knee, other knee and leg symptoms can occur. This can affect your ability to walk, climb stairs, and maintain balance easily. Symptoms can include:

  • Catching or locking sensation in the knee
  • Inability to bear weight on the leg
  • Knee pain, swelling, stiffness, or limited range of motion
  • Popping, crunching or creaking noises in the joint

Other symptoms that may occur along with knee buckling

Sometimes, knee instability results from diseases and conditions outside the knee. Symptoms can vary considerably depending on the underlying cause and may include:

  • Small lumps under the skin, especially around joints or bony areas
  • Widespread weakness

What causes buckling of the knee?

Knee instability can result from an injury, disease or condition that affects the knee. However, there are other possible causes of knee buckling. And many times, there is no clearly identifiable cause of feeling like the knee could give way.

Joint causes of knee buckling

Knee buckling may arise from problems in the knee joint including:

  • Knee dislocations and fractures
  • Ligament injuries, including torn ACL (anterior cruciate ligament), torn PCL (posterior cruciate ligament), and MCL (medial collateral ligament) tears and injuries
  • Loose bodies, which occur when bone or cartilage breaks off into the joint space
  • Meniscus and cartilage tears
  • Patellar instability, leading to kneecap dislocations

Other causes of knee buckling

Sometimes, knee instability can arise from problems outside the knee itself including:

  • Balance problems
  • Deconditioned state (“out of shape”), leading to muscle weakness
  • Nerve problems

In some cases, knee buckling may be a symptom of a serious injury. It also increases the risk of falls and more injury, such as a fracture. See your doctor promptly if you have knee instability. Seek immediate medical care if you have an injury involving the knee.

When should you see a doctor for knee buckling?

Knee buckling can be a sign of an underlying knee injury or disease. People with knee instability are also more likely to fall and sustain another injury. The safest option for dealing with knee buckling is to make an appointment with your doctor. Your doctor can determine the extent of any injury or disease and diagnose any potentially serious problems.

Call 911 or go to your nearest emergency room or urgent care facility for an injury affecting the knee.

How do doctors diagnose the cause of knee buckling?

To diagnose the cause of knee buckling, your doctor may ask you several questions related to your knee including:

  • How long has your knee felt unstable?
  • How often do you feel like your knee will give out?
  • Did you experience an injury to your knee?
  • Are you experiencing any other symptoms, such as pain or stiffness?
  • When do your symptoms occur?
  • What, if anything, makes your symptoms better or worse?
  • Have you fallen as a result of knee buckling?

Your doctor will also examine your knee to look for signs of injury. Part of the exam may involve moving your knee and testing how far the joint can go in different directions. In some cases, it may be necessary to have imaging exams, such as X-rays, ultrasounds, CT (computerized tomography) scans, or MRIs (magnetic resonance imaging).

It is not always possible to diagnose an underlying cause or condition. If the problem persists and your provider is unable to determine a cause, seeking a second opinion may give you more information and answers.

What are the treatments for knee buckling?

Treating knee buckling depends on the severity of the problem and the underlying cause. The goals are to restore stability, prevent falls, and relieve any accompanying symptoms. In general, doctors start with conservative treatments including:

  • Rest, ice and elevation to reduce pain or swelling from minor injuries
  • NSAIDs (nonsteroidal anti-inflammatory drugs), such as ibuprofen (Advil, Motrin) and naproxen (Aleve), to help relieve pain and swelling
  • Bracing to support the knee and keep it stable
  • Crutches to keep weight off the knee if necessary

In some cases, surgery may be necessary to correct the problem causing knee instability if conservative treatments fail.

If body weight is contributing to knee instability, doctors may recommend a comprehensive weight loss program.

What are some home remedies for knee buckling?

It’s a good idea to see a doctor for knee buckling. This is especially true if you are older, frail, or if the problem is recurrent. Self-care tips for managing a minor problem include:

  • Rest: If knee buckling happened with a specific activity, take a break from it. Give your knee time to heal before returning to the activity.
  • Ice: Applying an ice pack to your knee several times a day for 20 minutes at a time can relieve pain and inflammation.
  • Elevation: Prop your knee up while you are sitting to reduce swelling.
  • Heat: Some people find that heat helps relieve pain from minor injuries. You may alternate ice and heat.
  • Over-the-counter pain relievers: In general, NSAIDs are most useful for relieving pain and swelling from minor injuries. If you can’t take NSAIDs, acetaminophen (Tylenol) may be helpful.

What are the potential complications of knee buckling?

The main complication of knee instability is losing your balance and falling. Falling increases the risk of further injury, including fractures. People most at risk of falling include the elderly and those who have recurrent episodes of knee buckling.

Untreated knee injuries can accelerate the development of knee osteoarthritis and worsening mobility. Persistent knee instability can also limit your ability to climb stairs. Fear of falling or losing your balance may cause many people to avoid activities, including work and leisure interests.

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Medical Reviewer: William C. Lloyd III, MD, FACS
Last Review Date: 2021 Mar 18
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THIS TOOL DOES NOT PROVIDE MEDICAL ADVICE. It is intended for informational purposes only. It is not a substitute for professional medical advice, diagnosis or treatment. Never ignore professional medical advice in seeking treatment because of something you have read on the site. If you think you may have a medical emergency, immediately call your doctor or dial 911.
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