Instability of knee is usually referred to a sense of looseness, giving away of the knee or abnormal opening during certain activities.
Stability of the knee joint is maintained by the shape of the menisci, knee cap, condyles, muscles and ligaments that support the structure of knee joint. Injury to any one or more of these supporting structures can cause instability in the knee. Osteoarthritis of knee is also associated with instability. Osteoarthritis causes loosening of cartilage bodies inside the knee, degeneration of meniscus and muscular weakness. Small loose bodies of calcified cartilage due to osteoarthritis can be caught between the bones of knee, I the joint space, causing sudden pain and sensation of knee giving way. These loose bodies can also cause locking of the knee ad may interfere with straightening of the leg.
Most common cause of knee instability is injury of ligaments. Other causes may include tears of meniscus, patellar injury/instability or swelling in the knee. Swelling also referred as “water on the knee” can also make the joint feel unstable by increasing the space between shin bone, thigh bone and patella (knee cap). Ligament tears, meniscus tears, paella dislocations and fractures are common causes of swelling of the knee which in turn can instability of this hinge joint.
While ligament injuries, common amongst athletes, are often caused by sudden stopping, twisting, hyperextending or hyper flexing, meniscus tears can occur due to an injury, minor traumas or even squatting deeply.
Instability of patella or unstable knee cap can occur due to abnormally shaped or abnormally aligned knee. Knee cap dislocations are also common amongst young athletes and can lead to recurrent episodes of knee instability.
Generally, treatment of knee instability depends on the extent or grade of the instability and whether or not the injury is chronic or acute. Mild to moderate injuries that cause instability may be treated with anti-inflammatory medications, ice, bracing, and physical therapy. Severe or most grade 3 injuries causing instability typically require surgical reconstruction or repair.