The patella, or kneecap, is a small bone embedded within the quadriceps tendon. It acts as a pulley to enhance muscle function in straightening the leg and protects underlying knee joint structures. Patella alta is a condition related to the position of this kneecap.
Understanding Patella Alta
Patella alta, also known as a “high-riding patella,” describes a condition where the kneecap sits abnormally high relative to the thigh bone (femur). Instead of resting snugly within the femoral trochlear groove, the patella is elevated, often residing in a shallower part or even above it. This means the patella does not engage fully with the groove.
Causes of patella alta vary. It is often a congenital or developmental condition, meaning individuals are born with it, frequently due to an abnormally long patellar tendon. Other factors include growth abnormalities, such as those affecting growth plates, knee trauma, and chronic conditions like patellar tendinitis. Muscle imbalances, such as quadriceps weakness, may also contribute.
Recognizing Symptoms and Diagnosis
Individuals with patella alta often experience anterior knee pain, especially during activities involving bending or loading the knee, such as squatting or climbing stairs. A sensation of instability or the feeling that the knee might “give way” is also common. Some may notice a grinding or popping sensation (crepitus) as the patella moves.
Diagnosing patella alta involves clinical assessment and imaging. A healthcare provider performs a physical examination to evaluate knee range of motion, stability, and patella movement. Imaging confirms the diagnosis and assesses severity.
X-rays, particularly lateral radiographs taken with the knee flexed at 30 degrees, are common. These images allow for measurement of specific ratios, such as the Insall-Salvati ratio, which indicate patella alta. MRI and CT scans provide detailed views of soft tissues and bone structures, helping identify associated damage.
Severity and Potential Complications
The seriousness of patella alta varies. The elevated patella disrupts normal knee joint mechanics, as it does not properly engage with the femoral trochlear groove. This improper tracking makes the patella less stable and prone to excessive movement.
If unaddressed, patella alta can lead to long-term complications. A significant concern is an increased risk of patellar dislocation or subluxation, where the kneecap partially or completely slips out of position. This occurs because the high-riding patella lacks the bony stability of the deeper groove, making it more prone to displacement.
Patellofemoral pain syndrome (PFPS), characterized by pain around or behind the kneecap, is also associated with patella alta. Abnormal tracking and increased pressure on patellar cartilage can lead to irritation and inflammation. Over time, this altered biomechanics can contribute to premature wear of articular cartilage, potentially leading to patellofemoral osteoarthritis. Patella alta is linked to an elevated prevalence of osteoarthritis in the knee joint and can predict worsening cartilage damage, particularly in the lateral patellofemoral joint.
Management and Treatment Approaches
Managing patella alta often begins with conservative, non-surgical approaches. Physical therapy is a primary treatment, focusing on strengthening muscles around the knee, particularly the quadriceps and glutes, to improve patellar alignment and stability. Stretching exercises for hamstrings and calves are also included.
Bracing or taping can help stabilize the kneecap and improve tracking, reducing pain. Pain management, including nonsteroidal anti-inflammatory drugs (NSAIDs), may reduce pain and inflammation. Activity modification, such as avoiding aggravating activities, is also beneficial.
When conservative treatments are ineffective or in severe cases, surgical options may be considered. A common procedure is a tibial tubercle osteotomy, which repositions the patellar tendon’s attachment point on the shinbone downwards. This improves patella engagement and reduces instability. Other interventions include medial patellofemoral ligament (MPFL) reconstruction, which reinforces the main stabilizing ligament, or patellar tendon imbrication, which shortens the patellar tendon. A medical evaluation determines the most appropriate treatment plan.