Weak in the Knees: Causes and Solutions for Knee Buckling

Eric Jackson

Jun 30

Breaking Down the Knee Joint

To better understand what is causing your sudden knee buckling, it helps to learn the basics of the knee joint.

At the knee joint, three bones intersect to form a complex structure that supports your weight and enables movement in the legs. These bones include the femur, also known as the thigh bone; the tibia, or shin bone; and the patella, commonly referred to as the kneecap. The patella is positioned at the front of the knee, acting as a protective shield for the delicate structures within the joint. The patella acts as a fulcrum to assist knee movement and as such can see very high forces.

The bones of the knee joint are held together and supported by a network of ligaments. These ligaments help maintain the knee's stability. In total, there are four main ligaments in the knee:

Anterior cruciate ligament (ACL)
Lateral collateral ligament (LCL)
Medial collateral ligament (MCL)
Posterior cruciate ligament (PCL)

The collateral ligaments (the LCL and MCL) are found on the sides of the knee. The LCL is located on the outer side, and the MCL is located on the inner side. The cruciate ligaments (ACL and PCL) form an X on the inside of the knee joint. The ACL is in the front, and the PCL is in the back.

Together, all of these ligaments work to provide stability, strength and mobility to the knee joint.

The Hidden Culprits Behind Knee Buckling

Knee buckling is often attributed to osteoarthritis, a common type of arthritis, but it can also be a symptom of a knee injury. Buckling of the knee often represents a natural response to dysfunction in the knee, acting like a circuit breaker.

Here are some reasons why your knee may be suddenly giving way:

Ligament injury. A ligament injury, such as an ACL tear, can cause knee instability and sudden knee buckling. An ACL tear is one of the most common knee injuries, according to the American Academy of Orthopaedic Surgeons.
Meniscus tear. The meniscus is cartilage that sits between the thigh and shin bone and absorbs shock whenever you walk, jump, run, etc. Meniscus tears often happen while playing sports when turning suddenly, but they can also happen from an awkward twist of the knee when bending or standing up. Common symptoms include pain, stiffness and a feeling like your knee is giving way. Your knee may also feel like it is locking up.
Osteoarthritis. Over 32.5 million adults in the United States have this common wear and tear type of arthritis, according to the Centers for Disease Control and Prevention. Osteoarthritis is characterized by pain, stiffness and inflammation. Knee buckling is common in people who have osteoarthritis. Wear of the cartilage of the kneecap, known as chondromalacia patella, is the most frequent cause of buckling.
Plica syndrome. This a syndrome that represents thickening of the knee's lining, creating irritation to the cartilage. Common symptoms of plica syndrome are pain, swelling and knee instability, which can lead to knee buckling.

Other causes for knee buckling can include instability, or poor tracking, of the kneecap, and issues with the nerve control of the thigh muscles. Examples of nerve issues include pinching in the spine and progressive neurologic conditions.

Steps to Restore Stability After Knee Buckling

The treatment you need to fix your knee giving out varies based on your knee injury or condition. In general, home exercises and physical therapy seek to strengthen the muscles of the thigh to aid in knee control. Supportive devices, such as knee braces and crutches, may also help when walking.

If you have sustained a knee injury, such as an ACL or meniscus tear, you can try RICE:

Rest. Take a pause on activity and prevent putting any weight on your leg.
Ice. Apply cold packs in 20-minute intervals multiple times throughout the day. Avoid putting ice directly on the skin.
Compression. To minimize swelling, put compression on the knee with an elastic compression bandage. But make sure it is not too tight.
Elevation. In order to decrease swelling, elevate your leg higher than your heart and recline while resting.

Stay Steady on Your Feet

To help prevent knee injury or disease that can lead to knee buckling, it may help to strengthen the quadriceps muscles (muscles on the front of the thigh), the hamstrings (muscles on the back of the thigh), the calves (muscles on the back of the lower legs), and the gluteal muscles (muscles in the buttocks). A great exercise that targets these muscles is a squat. If you're new to exercise, try just squatting with your body weight and add weights as you improve muscle strength.

To further help your knees, reach or maintain a healthy weight. Every pound of weight adds four pounds of stress to your knees. To reach a healthy weight, you may need to make some changes to live a healthy lifestyle. Try improving your diet to eat plenty of vegetables, fruit, lean proteins (such as chicken, turkey and fish), whole grains, and low and non-fat dairy. Also, try to get at least 30 minutes of physical activity five days a week.

If you're doing what you can to prevent knee injury and disease, but you're still having issues with knee buckling, it may be time to see an orthopedic specialist.