Patellofemoral maltracking occurs when the kneecap (patella) does not move smoothly within the trochlear groove of the thigh bone during knee movement. Instead of gliding centrally, the patella often shifts to the side, typically outwards. This improper movement causes friction and increased pressure on the joint surfaces, leading to discomfort and potential damage. This condition is also known as patellar tracking disorder or patellofemoral pain syndrome.
Symptoms and Mechanical Issues
Individuals experiencing patellofemoral maltracking often report pain at the front of the knee, which worsens with activities involving bending the knee. This includes climbing stairs, squatting, or sitting for extended periods. A grinding, popping, or catching sensation may be felt or heard when the knee moves. Some people also describe instability, as if the knee could give way, or observe visible swelling around the kneecap.
The mechanical problem involves the interaction between the patella and the trochlear groove of the femur. When maltracking occurs, the kneecap commonly shifts laterally. This lateral deviation causes increased load and uneven forces on the articular cartilage surfaces of the patellofemoral joint. The resulting friction and pressure can lead to irritation, inflammation, and eventual wear and tear on the cartilage.
Underlying Causes of Maltracking
Several factors can contribute to patellofemoral maltracking, often in combination. Muscular imbalances around the thigh and hip are a common cause. Weakness in the vastus medialis obliquus (VMO), the inner quadriceps muscle, reduces its ability to pull the patella medially. This weakness, combined with tightness in outer thigh structures like the vastus lateralis or the iliotibial band (IT band), can pull the patella off-center.
Anatomical variations also predispose individuals to maltracking. A high-riding patella (patella alta) sits higher than normal, affecting its engagement with the trochlear groove. A shallow trochlear groove or a misshapen patella can also reduce stability. Alignment issues, such as an increased Q-angle, can increase the lateral pull on the patella.
Trauma to the knee can also initiate or worsen patellar maltracking. A direct blow or previous patellar dislocation can damage ligaments and soft tissues that stabilize the patella. Injury to the medial patellofemoral ligament (MPFL), a primary restraint against lateral patellar movement, is often associated with lateral patellar dislocations. Such injuries can disrupt normal mechanics, leading to chronic instability.
Evaluation and Management
Diagnosis of patellofemoral maltracking begins with a physical examination. The doctor observes knee movement, assesses muscle strength and flexibility, and may check for signs like a “J-sign,” where the patella veers laterally as the knee extends. Imaging studies, such as X-rays, show bony alignment, patellar height, and trochlear groove shape. An MRI evaluates soft tissues like ligaments and cartilage, and helps rule out other conditions.
Management of patellofemoral maltracking focuses on non-surgical approaches to restore knee function and reduce pain. Physical therapy is a common and effective treatment, aiming to strengthen specific muscles and improve overall lower limb mechanics. Exercises often target the vastus medialis obliquus (VMO) to enhance its ability to stabilize the patella medially, alongside strengthening hip abductor muscles to improve hip alignment. Stretching tight structures like the IT band and hamstrings is also incorporated to reduce external pulling forces on the patella.
In addition to exercises, patellar taping or bracing can guide the kneecap into an optimal position during movement, providing temporary support and reducing pain. These external supports are helpful during activities that aggravate symptoms. While conservative treatments are successful for many, surgery may be considered for severe or persistent cases that do not respond to non-surgical care. Surgical options aim to realign the patella or repair damaged stabilizing structures, such as reconstructing the medial patellofemoral ligament.