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Buckling Knee Symptoms, Causes & Common Questions

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Last updated May 4, 2022

Buckling knee quiz

Take a quiz to find out what's causing your buckling knee.

Understand your buckling knee symptoms, including 8 causes & common questions.

Buckling knee quiz

Take a quiz to find out what's causing your buckling knee.

Take buckling knee quiz

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Buckling knee symptoms

How embarrassing! You were just walking down the street, minding your own business, when your knee gave out on you. You slipped and fell in front of what felt like half the town. In all honesty, the only person who saw you was the mailman.

What you've just experienced is a buckling knee. It can occur to just about anyone and at just about any time. But if you become someone who experiences knee buckling on a regular basis, you'll find out that the event is annoying embarrassing, potentially dangerous, and becomes more concerning the more it happens.

Common characteristics of a buckling knee

If you think you have a buckling knee, you might be experiencing:

  • Loss of knee strength when weight is placed on it
  • Pain surrounding the knee
  • Difficulty standing or walking properly
  • Knee Swelling or inflammation
  • Cracking or popping sound from the knee when being stretched or flexed

Knee function and anatomy

Our knees bear quite a bit over the course of our lifetime. Some of the most important bones in our body meet at the knee. The kneecap, or patella, sits in front of the femur and tibia. The leg bones meet directly behind the patella where they are cushioned with articular cartilage and the bones are connected by the anterior cruciate ligament and patellar tendon.

These parts usually work in harmony as they should, allowing a fluid motion that results in the bending of the knee that's required for walking or running. But when something is damaged or just not working right, the result can be a knee that can't function properly that buckles instead of bends.

Let's determine the cause of your buckling knee so that you can treat any possible existing condition. Hopefully you can prevent this phenomenon from occurring again, especially at an important time like your wedding or graduation.

Buckling knee causes

If your buckling knee seems like an isolated incident, you might not need to or be able to determine a cause quite yet.

But if your knee seems to be giving you problems on a regular basis, consider the following cause categories.

Traumatic causes

Whether you're a seasoned athlete or hit the gym once a month, moving your knee in the wrong direction can cause trauma that leads to an unstable knee joint. In mild cases, a little rest should solve the problem. But in more serious traumas, such as when a ligament or tendon is damaged, healing can take more effort and time.

Serious medical causes

Serious medical causes are rare, but they are possible.

  • Calcium build-up: A treatable example would be chondrocalcinosis, which is a build-up of calcium in the knee.
  • Arthritis: This is another common medical cause behind a buckling knee. Arthritis isn't curable but there are ways to minimize its effects on the body.


There are other causes behind buckling knees that aren't related to trauma or disease. Aging can be a factor. It's incredibly rare for a child to experience a buckling knee, but for those much further along in life, a buckling knee can be just another aging symptom like wrinkles or hair loss.

This list does not constitute medical advice and may not accurately represent what you have.

Patellofemoral pain syndrome

Patellofemoral pain syndrome (PFPS) is also called runner's knee, jumper's knee, anterior knee pain, chondromalacia patella, and patellofemoral joint syndrome.

Overuse through training for sports is a common cause, especially if there is a misalignment in the knee joint or a previous knee injury. This wears away the cartilage beneath the kneecap and causes pain on exercising.

It is most common in females and in young adults who are active in sports, but can affect anyone.

Symptoms include dull pain at the front of the knee and around the kneecap (patella) while running, squatting, or climbing stairs, or after prolonged sitting with knees bent.

Diagnosis is made through physical examination and through x-rays, CT scan, and/or MRI.

Treatment most often involves rest; over-the-counter pain relievers; low-impact exercise such as swimming or bicycling; physical therapy to strengthen and stabilize the knee; and orthotics (shoe inserts) to help correct a misaligned stride.

Surgery is needed only for severe cases, and is done through arthroscopy to remove any fragments of damaged cartilage.

Rarity: Common

Top Symptoms: knee pain, pain in one knee, knee pain that gets worse when going up stairs, dull, achy knee pain, knee pain that gets worse when squatting

Symptoms that always occur with patellofemoral pain syndrome: knee pain

Urgency: Primary care doctor

Meniscal injury

The menisci are the two pieces of cartilage serving as shock absorbers in the knee, between the lower end of the thighbone and the top of the shinbone. A torn meniscus is commonly referred to as "torn cartilage" in the knee.

Damage to a meniscus often happens along with another injury to the knee, especially when there is any forceful, twisting movement or a direct hit such as a tackle.

Older people may tear a meniscus through normal activity if the cartilage has become thin and worn due to aging.

Symptoms include pain, stiffness, and swelling. The knee will simply not work correctly and may catch, lock up, or give way.

Diagnosis is made through patient history, physical examination, simple motion tests, and imaging such as x-ray or MRI.

Depending on the exact form of the injury, the tear may be allowed to heal on its own with supportive care such as rest, ice, and nonsteroidal anti-inflammatory pain medication. In other cases, arthroscopic surgery followed by rehabilitation may be needed.

Rarity: Common

Top Symptoms: pain in one knee, knee stiffness, knee instability, pain in the inside of the knee, swollen knee

Urgency: Primary care doctor

Knee sprain (LCL)

The LCL is the ligament on the outside of the knee, keeping it from bending away from the body. It is most commonly injured while playing sports (ouch!) when a force is placed on the knee from the inner half of the knee.

Depending on the severity of your knee pain, you should go see your doctor or go to an urgent care clinic as soon as possible. Your doctor may prescribe you crutches, a brace, pain medication, or physical therapy. You may be asked to refrain from physical activity.

Rarity: Rare

Top Symptoms: pain in one knee, knee pain from an injury, knee injury, pain in the outside of the knee, sports injury

Symptoms that always occur with knee sprain (lcl): pain in one knee, knee pain from an injury

Symptoms that never occur with knee sprain (lcl): mild knee pain

Urgency: Hospital emergency room

Knee arthritis

Knee arthritis means that there is inflammation and abnormal wear of one or both of the two joints in the knee.

Arthritis in any joint is most often be caused by long-term wear and tear, called osteoarthritis; by an autoimmune condition that attacks the joints, called rheumatoid arthritis; or by an injury, called post-traumatic arthritis.

Symptoms include pain, which becomes worse with use of the joint; limited range of motion, meaning the shoulder joint cannot move as far as it once did; and pain when resting or trying to sleep.

Knee arthritis cannot be cured, but symptoms can be managed to improve quality of life and ease pain and discomfort.

Diagnosis is made through patient history, physical examination, and x-rays. To confirm, an injection of anesthetic may be placed into the joint. If the pain is eased, arthritis is almost certainly the cause.

Treatment involves physical therapy; nonsteroidal anti-inflammatory drugs to ease discomfort and inflammation; and corticosteroid injections into the knee to relieve pain. Surgery and knee joint replacement can be done in some cases.

Rarity: Common

Top Symptoms: pain in both knees, knee stiffness, knee instability, swollen knee, morning joint stiffness

Symptoms that always occur with knee arthritis: pain in both knees

Urgency: Primary care doctor

Dislocated kneecap

The kneecap connects the muscles in the front of the thigh to the shinbone (tibia). When the slips out of the groove, problems and pain often result.

You should visit your primary care physician within the next 24 hours. The first step is to return the kneecap to its proper place, a process called reduction.

Acl injury

The ACL (anterior cruciate ligament) is an important tendon that connects the femur (thigh bone) to the tibia (shin), stabilizing the knee. ACL injuries are commonly caused by sports-related injuries.

Your primary care provider or an urgent care provider can do an exam, and imaging can determine the extent of the injury. Treatment depends on the severity of the injury, ranging from rehabilitation to full surgery.

Rarity: Rare

Top Symptoms: knee pain, pain in one knee, knee instability, swollen knee, knee pain from an injury

Symptoms that always occur with acl injury: knee pain

Symptoms that never occur with acl injury: mild knee pain

Urgency: Hospital emergency room

Knee (mcl) sprain

The medical collateral ligament (MCL) links the thigh bone and the shin bone on the inner side of the knee joint. An MCL sprain is any damage done to this ligament (usually through twisting/force during sports).

Rarity: Uncommon

Top Symptoms: pain in one knee, knee pain from an injury, knee injury, pain in the inside of the knee, sports injury

Symptoms that always occur with knee (mcl) sprain: pain in one knee, knee pain from an injury

Symptoms that never occur with knee (mcl) sprain: mild knee pain

Urgency: Primary care doctor

Repeated kneecap dislocation (patellar subluxation)

Recurrent patellar subluxation is the continued instability of the kneecap, which causes anterior knee pain and usually occurs laterally. It occurs unpredictably with varying durations.

Rarity: Uncommon

Top Symptoms: pain in one knee, dull, achy knee pain, pain in the front of the knee, pain in the inside of the knee, swollen knee

Symptoms that always occur with repeated kneecap dislocation (patellar subluxation): kneecap dislocation

Urgency: Primary care doctor

Buckling knee treatments and relief

You should never ignore a buckling knee. In most cases, home treatment is all you need. But there are signs that point to a necessary doctor's visit.

When to see a doctor for knee buckling

Seek care as soon as possible for any of the following:

  • Extreme pain
  • Unusual swelling
  • An increase in buckling incidents
  • An unnatural appearance of the knee: Such as bulges or large bumps
  • Unable to walk without assistance

Treatments for a buckling knee

The following treatments could have your knee functioning properly again. If your knee buckling worsens or persists, you should see your doctor for professional treatments as soon as possible.

  • RICE Technique: The RICE method can be applied if an injury is suspected. Rest the knee, ice it for 20 minutes at a time, use compression when possible, and keep the leg elevated.
  • Medication: If the pain is intense, NSAIDs, such as ibuprofen (Advil, Motrin), can be taken for relief.
  • Supportive device: If further support is needed, knee braces can be used to facilitate movement while the tissues are healing.
  • Surgery: Severe cases may require surgery. If there are bone or tissue fragments present in the joint, surgical removal is needed to prevent further injury and restore the fluid motion of the knee.

Knee buckling is a simple health issue, but learning its cause and determining a treatment can save you from annoying and embarrassing moments. If your knee isn't improving on its own, it may get worse with time, so start the search for a cause and cure sooner than later.

FAQs about buckling knee

What does it mean when your knees lock up?

Knee locking is most commonly caused by meniscal tears, often from a traumatic incident or constant wear and tear. Knee buckling can be a sign of osteoarthritis of the knee, tears of a portion of cartilage called the "meniscus," or a tear if a ligament or muscle. These tears can often be contoured or repaired by orthopedic surgeons, and if knee locking is severely limiting your mobility, you may want to consider surgery.

Can arthritis lead to knee buckling?

Osteoarthritis or arthritis from old age can lead to knee buckling. Osteoarthritis is caused from inflammation and a wearing away of the cartilage of the "articular" contact surfaces of the joints. It happens frequently in the hips and knees. This loss of cartilage and break down of bones on the surfaces where they contact each other can "roughen" the surfaces, and cause them to catch on each other causing knee buckling.

Can buckling knees mean a torn ligament?

Yes. A torn ligament can cause knee buckling as it can destabilize connections between bones. More commonly, a torn tendon will cause knee buckling, because tendons attach muscle to bone, and detaching muscle from bone will keep a muscle from being able to exert force on a knee. If you tear a tendon, you may also have a bulge of the associated muscle as it is no longer connected to bone. It may bunch in an area of the leg or arm causing a grossly enlarged muscle, often called the "Popeye" effect after the cartoon character whose muscles buldged out after eating spinach.

What does it mean if your knees give out?

Knees can give out for a variety of reasons. The body monitors the amount of force placed on a muscle, and in certain situations, if you exceed that force, the muscle will "give out" to protect itself from being torn. However, a knee will also give out if a muscle is torn, or can give out from wear and tear on bones from osteoarthritis.

When should you seek medical attention for buckling knees?

Knee buckling in the absence of strenuous activity is abnormal and you should seek medical attention if this happens. If your knees buckle during strenuous activity, and you experience residual pain, "grinding," inability to bear weight, or knee locking, you should seek medical attention. The doctor may test the "range of motion" of the knee or move it through a series of positions to evaluate it and then help you develop a treatment plan or refer you to a specialist.

Questions your doctor may ask about buckling knee

  • Do you feel like your knee is unstable, weak, or giving out?
  • What is your body mass?
  • While you are standing, take a look at your knees. Do they appear to bend towards each other, rather than follow a straight line along your legs? (Knock-kneed)
  • Did you feel your knee cap pop out of place?

Self-diagnose with our free Buoy Assistant if you answer yes on any of these questions.

Hear what 1 other is saying
Once your story receives approval from our editors, it will exist on Buoy as a helpful resource for others who may experience something similar.
The stories shared below are not written by Buoy employees. Buoy does not endorse any of the information in these stories. Whenever you have questions or concerns about a medical condition, you should always contact your doctor or a healthcare provider.
Knee buckles without any warningPosted March 31, 2020 by R.
Male age 53. About 3 months ago, my right knee started buckling. At first I though it was just an isolated instance. Because after a quick sharp pain and nearly falling to the ground within 5 or 10 seconds, the pain would go away as fast as it came. Now fast forward 3 months. My knee buckles 5 or more times a day. It comes without any warning and almost takes me to the ground. I have full range of motion and no swelling or redness. My job has me going up and down ladders frequently, but it has not given way while assenting or descending a ladder. However, that is a growing fear. My back story, though I don’t know if there is any relevance, is that I suffer from chronic lower and middle back pain, lower lumbar degeneration, as well as my spine between my shoulder blades that is fusing together. I have mild scoliosis and stenosis. I also experience neuropathy in both feet. I work 40 plus hours a week, so I am not sedentary. I am on opiates, muscle relaxers and cymbalta to carry on as close to normal as I can. What can cause your knee to buckle without warning or any lasting pain or swelling? My fear is that I will eventually fall and cause serious injury. I really like my job, but I am becoming fearful of using ladders. What can I do to prevent my knee from giving way?
Dr. Rothschild has been a faculty member at Brigham and Women’s Hospital where he is an Associate Professor of Medicine at Harvard Medical School. He currently practices as a hospitalist at Newton Wellesley Hospital. In 1978, Dr. Rothschild received his MD at the Medical College of Wisconsin and trained in internal medicine followed by a fellowship in critical care medicine. He also received an MP...
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