Patellar Instability

The kneecap, or patella, plays a vital role in how the knee functions. Although it might seem like a small, floating bone on the front of the joint, it performs several essential mechanical and protective functions that make normal walking, running, and bending possible.

The kneecap is essential for power, protection, and efficiency. It allows your legs to move effectively while safeguarding the knee’s delicate structures. When the patella becomes unstable, fractured, or misaligned, even simple activities can become painful and difficult—highlighting just how crucial this small bone is to everyday movement.

People with patellar instability often describe a feeling that their kneecap is shifting or sliding out of place, especially during activities such as running, jumping, or pivoting. In more severe cases, the patella may fully dislocate, visibly moving to the outside of the knee joint. Common symptoms include:

• A feeling that the knee is giving way or unstable during movement
• Pain in the front of the knee, particularly when climbing stairs or squatting
• Swelling or stiffness after activity or injury
• A popping sensation or visible movement of the kneecap during dislocation
• Difficulty straightening the knee after the kneecap shifts
• Ongoing discomfort or apprehension when bending or twisting the knee

Even if the kneecap slips back into place on its own, repeated instability can stretch or tear the surrounding ligaments, making future episodes more likely.

Patellar instability may result from trauma, repetitive stress, or anatomical differences in the knee. In athletes, it often follows a twisting injury or direct blow to the knee. In others, it may develop gradually due to natural variations in bone structure or muscle balance. Common causes include:

• Trauma or injury: A sudden blow to the knee or a twisting motion can push the kneecap out of its normal alignment, stretching or tearing stabilizing ligaments.
• Shallow femoral groove: Some individuals are born with a trochlear groove that is flatter than normal, giving the patella less stability during movement.
• Ligament laxity: Looser ligaments, whether naturally occurring or due to injury, allow more movement of the kneecap.
• Muscle imbalance: Weakness in the quadriceps, particularly the inner thigh muscle (vastus medialis obliquus), can cause the kneecap to pull more toward the outside of the knee.
• High-riding kneecap (patella alta): If the patella sits higher on the femur than usual, it may not engage properly in the groove, increasing the risk of instability.
• Repetitive stress: Overuse or repeated movements, especially in sports involving cutting or jumping, can wear down stabilizing tissues and lead to chronic instability.

While anyone can experience patellar instability, certain factors increase the likelihood of developing this condition. These include:

• Age: It most commonly affects adolescents and young adults, especially those who participate in sports.
• Gender: Females tend to have a higher risk, possibly due to anatomical differences in hip and knee alignment.
• Activity level: Athletes in sports requiring rapid changes in direction—such as soccer, basketball, or gymnastics—are more prone to knee instability.
• Previous dislocations: Once a patella has dislocated, the risk of recurrence increases significantly.
• Genetics or bone structure: Family history or congenital differences in bone shape can contribute to instability.

If not properly evaluated and treated, patellar instability can lead to long-term problems in the knee. Repeated dislocations stretch and weaken the ligaments that hold the kneecap in place, increasing the frequency and severity of future episodes. Over time, the cartilage underneath the patella can become damaged, leading to chronic pain and early arthritis. Some patients also experience loss of confidence in the knee, limiting their ability to participate in sports or even daily activities.