Have you ever felt your knee just give out, leaving you struggling to stand? Knee buckling refers to the sensation of instability or sudden loss of stability in the knee joint, often causing the leg to give way momentarily while you are walking or doing other routine activities. This can happen for a variety of reasons, usually an injury or other damage to one of the knee’s supportive structures, such as a ligament or meniscus…or because the knee is weak from the effects of arthritis or a lack of muscle tone.
Bottom Line Personal asked orthopedic surgeon Jorge Chahla, MD, PhD, how this happens…what to do about it…and, better yet, how to prevent it.
The knee relies on key structures to function properly, and damage to any one of those structures from an accident or sports injury, for instance, can cause knee buckling.
Each knee has four main ligaments—the medial and lateral collateral ligaments that provide stability against side-to-side forces…and the anterior and posterior cruciate ligaments—commonly known as the ACL and PCL, respectively—that maintain front-to-back stability. Damage to any of these structures can compromise a knee’s stability and lead to sudden knee buckling and other symptoms.
The collateral ligaments are more likely to heal when the injury occurs on the inside of the knee than when the injury is to the anterior and posterior cruciate ligaments because they have better healing capacity in the surrounding tissues. Treatment strategies depend on the injury’s severity and location and can range from immobilization using a hinged knee brace…to surgical repair or reconstruction, particularly when there is significant damage or instability.
ACL tears are commonly treated with ACL reconstruction, the best approach for restoring knee stability and function.
Partial, or incomplete, PCL injuries may be managed with conservative methods, such as bracing and physical therapy. The PCL’s proximity to good blood supply, supported by the surrounding synovium (the soft lining of the joint), gives it a good chance of healing without surgery. In the case of a full-thickness PCL tears, surgical reconstruction is more likely, especially when there’s also damage to other ligaments or a meniscus (see below).
Important: The trauma of an ACL or PCL injury increases risk for arthritis. While reconstruction cannot entirely prevent arthritis, it can significantly delay its onset by restoring stability and reducing the mechanical stress on the joint.
Although knee instability is frequently associated with ligament damage, it also can result from an injury to a meniscus. Each knee has two of these fibrocartilaginous structures, which serve as shock absorbers and contribute to overall knee stability. A meniscus injury, from a sprain to a tear, can predispose the knee to buckling episodes, and the greater the injury, the greater the instability. Example: Named for its floppy appearance, a bucket handle tear in the meniscus can lead not only to buckling but also catching or locking (when the flap of the meniscus gets caught in the knee joint and locks it into one position). Tears require urgent repair, not only when you can’t move the knee but even in less severe cases—delaying treatment diminishes the natural healing potential and can lead to poorer long-term outcomes.
Osteoarthritis is a degenerative condition that causes loss of joint cartilage and ensuing pain as joint bones rub against each other. That pain can cause you to change the way you move and lead to muscle imbalances. This disruption in muscle coordination weakens the dynamic stabilizing forces of the knee, increasing the feeling of instability. Separately (though often simultaneously), uneven cartilage degeneration may alter joint mechanics, increasing instability and the perception of your knee buckling. Addressing all aspects of arthritis is needed to restore knee stability and function.
If you’re experiencing episodes of knee buckling, consult an orthopedist to determine and address the cause. Repeated instability events can exacerbate cartilage damage, accelerating the development—or worsening—of arthritis. The orthopedist will do a thorough evaluation, including specific physical examination maneuvers, to make a precise diagnosis and create a tailored treatment plan that addresses your specific situation.
There are steps you can take to avoid knee buckling and instability. If you’ve already experienced knee buckling, exercises will likely be part of your treatment plan. Maintaining an active lifestyle and strengthening the muscles around the knee play key roles in preventing injuries that could lead to knee buckling.
Strong leg muscles provide vital support to the knee joint, reducing ligament strain and cartilage damage. It is important to not only strengthen the quadriceps (the front thigh muscles) but also the hamstrings (the back thigh muscles). These muscles work together to stabilize the knee, especially during activities such as running or jumping. If one muscle group is much stronger than the other, it can lead to imbalances that increase injury risk.
If you’re overweight, weight loss can have a significant positive impact, especially if you have arthritis. By reducing the load on the knee joint, you help decrease pain and inflammation, which can improve overall knee function and reduce the feeling of instability. This improvement in symptoms can lead to better gait mechanics, making movement smoother and less painful. Moreover, weight loss can enhance the activation of surrounding muscles, particularly the quadriceps and hamstrings. This increased muscular support can further aid in providing stability to the joint, reducing the risk for instability and promoting overall knee health.
