A loose knee is a condition characterized by knee pain and instability, snapping and popping sounds, and a feeling of weakness in the knee. The condition is frequently caused by a traumatic injury, such as a sudden twist, which results in the dislocation of the knee cap or damage to the ligaments which hold the knee in place. Atraumatic, or non-injury conditions such as a loose joint or a misaligned kneecap, can also cause a loose knee.
The knee is the largest and most easily injured joint in the body. It is formed by four bones: the femur, or thigh bone; the tibia, or large shin bone; the fibula, or small shin bone; and the patella, or kneecap. A gelatinous piece of cartilage called the meniscus acts as a cushion between the bones. The joint is held firmly in place by the four ligaments, the medial collateral ligament (MCL), the anterior cruciate ligament (ACL), the lateral collateral ligament (LCL), and the posterior cruciate ligament (PCL).
The ACL and PCL stabilize the rotation of the knee, preventing it from sliding back and forth. The LCL and MCL, located on the sides of the knee, prevent the knee from sliding sideways. Injury to any of these can result in a loose knee which can buckle or give way. Most ligament injuries are caused by twisting, which can cause stretching or tears, called sprains. Minor stretches or partial tears are often treated by rest and stabilization with a brace or similar device, while complete tears may require surgery, and can make the knee more susceptible to future injury.
Another condition which can cause a loose knee is patellar tracking disorder, or a misaligned kneecap. This occurs when the kneecap shifts too far to the side of the leg when the leg is bending or straightening. The shifting can happen if the groove in the thigh bone in which the kneecap slides is too shallow, or if there is damage to the cartilage, tendons, ligaments or muscles that hold the kneecap in place. Some people may have a genetic tendency for developing patellar tracking disorder, though a severe blow to the side of the knee can also result in a misplaced knee cap.
In some cases, the displacement of the kneecap is obvious because the knee looks misshapen. Other symptoms include pain, an inability to straighten the knee, popping and clicking, and a feeling that the knee cannot support any weight. This condition can sometimes be treated with therapy. Ice and rest are used to reduce the swelling, then an exercise program designed to strengthen the muscles is recommended.
Surgery is usually not the first option chosen to repair a loose knee unless there is a complete tear of one of the ligaments. If surgery is required, it is always followed by an extensive period of physical therapy. There are a number of things that can be done to prevent a loose knee, however, such as moving the body when bending and lifting, rather than just twisting at the knee. Stretching before activities, maintaining a proper weight and regularly exercising to keep the muscles and tendons strong are also effective preventative measures.