The feeling of a loose knee cap is most commonly caused by an injury that has sprained or tore ligaments. A meniscal or anterior cruciate ligament (ACL) injury can also cause knee instability and pain. Read below for more information about causes and how to seek medical treatment for an unstable knee.
What Causes Knee Instability? Knee instability can be caused by damage to the supporting ligaments of the knee, osteoarthritis, or a mechanical issue.
Weakness in the Knee and Mechanical Problems. Besides overuse, causes of knee pain include mechanical problems, like muscle imbalance or a loose piece of cartilage in the joint, and knee injuries—from torn ligaments to meniscal tears.
The medial cruciate ligament, or MCL, extends down the inside of the knee, connecting the femur to the tibia. This ligament prevents the knee joint from rotating too far from the inside. So when the MCL is injured, you may feel like your knee is about to collapse inward.
A chronic condition, in which the knee continues to be unstable, can often be corrected by surgery. For example, surgery can be used to realign and tighten tendons to keep the kneecap on track, or to release tissues that pull the kneecap off track.
Common causes of knee buckling
There are several culprits when it comes to knee buckling, including ligament and meniscus tears, arthritis, nerve damage, and plica syndrome.
Knee ligament tests involve a healthcare provider manually putting pressure on the four major ligaments of the knee to help determine if knee pain could be due to sprain or tear. Such tests include the anterior drawer test, the posterior drawer test, the valgus stress test, and the varus stress test.
Leg weakness can be caused by a variety of medical conditions, some of which are serious. Possible causes include stroke, systemic diseases, inflammatory conditions, nerve damage, muscle disorders, and medication side effects.
Redness or Swelling Around the Joint
Like deformity of your knee joint, changes in the shape and color of your knee can indicate serious problems. If you notice redness or swelling, touch the area to see if you feel any tenderness or warmth. These symptoms can be signs of infection.
Swelling and stiffness. Knee may catch, click, or lock. Knee may feel weak or unstable.
Nonsurgical treatments for knee instability can include physical therapy to strengthen the muscles around the knee joint and knee braces to better support the knee joint. Often, however, surgical treatment may be needed to restore the normal structure of the knee joint.
Problems with the joints, (such as arthritis), bones (such as deformities), circulation (such as peripheral vascular disease), or even pain can make it difficult to walk properly. Diseases or injuries to the nerves, muscles, brain, spinal cord, or inner ear can affect normal walking.
The weakness can make your legs feel heavy, as if they are being weighed down by something. They may also ache and hurt. Some people with MS describe it as like having bags of sand attached to their legs. This muscle weakness combined with MS fatigue can be upsetting.
It Could Be Articular Cartilage. If you feel something strange in your knee joint — like something's floating in there — it may be articular cartilage. Everyone has cartilage in their knees, but there could be an injury that requires medical attention.
Stand and then balance on one foot (the side you want to test). Perform a single-leg squat while trying to keep your body as straight as possible. If you're able to balance so that you're knee is straight about your hip for about one-half of the deep knee bend and the return up, then you pass the test on that side.
While there are more than 80 forms of arthritis, osteoarthritis and rheumatoid arthritis are both known to cause knee buckling in patients. Osteoarthritis is a degenerative condition that creates a breakdown in joint cartilage, leading to increased joint friction in the process.
A trick knee is a condition where your knee suddenly buckles beneath you. This means that your knee loses the ability to support your weight and gives out. In most cases, knee-buckling is associated with the existence of knee pain and can increase knee pain when it occurs.
A knee joint affected by arthritis may be painful and inflamed. Generally, the pain develops gradually over time, although sudden onset is also possible. There are other symptoms, as well: The joint may become stiff and swollen, making it difficult to bend and straighten the knee.
If left untreated, knee-buckling can cause serious harm to you and your loved ones, along with possible long-term damage in many areas of your body.
A knee brace can take pressure off the part of your joint most affected by osteoarthritis and help relieve pain. If your knee feels like it might buckle when you put weight on it, a knee brace can also help you stand and move around with more confidence.
Sudden weakness in the legs may be a sign of a medical emergency such as stroke or cauda equina syndrome and any sudden or unexplained leg weakness should warrant immediate medical attention.