The patella, or kneecap, is a shield-shaped bone embedded within the quadriceps tendon at the front of the knee joint. It increases the leverage of the quadriceps muscle, which is necessary for straightening the leg. For the knee to function smoothly, the patella must glide vertically within a specific channel on the thigh bone called the trochlear groove. Patellar tracking disorder occurs when the kneecap deviates from this normal, central path as the knee bends or straightens, resulting in misalignment (maltracking) within its groove.
The Mechanism of Patellar Tracking Disorder
The biomechanical failure that defines patellar tracking disorder occurs when the kneecap is pulled or shifted out of its intended track. In the majority of cases, this displacement occurs laterally, meaning the patella moves toward the outside of the leg.
When the patella moves outside the smooth trochlear groove, the cartilage on its underside begins to rub against the femur bone. This friction irritates the joint surface, a condition medically known as chondromalacia patellae. Over time, this repetitive grinding leads to softening and eventual breakdown of the protective articular cartilage.
Recognizable Symptoms and Signs
The most common symptom of patellar tracking disorder is a dull, aching pain felt directly beneath or around the kneecap. This pain typically worsens during activities that increase the load on the knee joint, such as climbing or descending stairs, squatting, or kneeling. Patients often experience what is known as the “theater sign,” where the pain becomes noticeable after a long period of sitting with the knees bent.
Mechanical symptoms are also frequently reported. These include a sensation of clicking, popping, or grinding, medically termed crepitus, which can often be heard or felt during knee movement. Furthermore, the knee may feel unstable, sometimes giving way or buckling unexpectedly because the patella is not secured within its groove.
Primary Causes and Contributing Risk Factors
Patellar tracking disorder is rarely caused by a single issue but rather a combination of muscular and structural factors. A primary cause involves a muscular imbalance in the thigh, specifically weakness in the vastus medialis obliquus (VMO), the innermost part of the quadriceps muscle. When the VMO is weak, the stronger, naturally tighter lateral structures, such as the vastus lateralis and the iliotibial (IT) band, pull the kneecap outward.
Anatomical variations can also predispose an individual to this condition. These structural issues include having a trochlear groove that is naturally too shallow to cradle the patella securely. Another factor is an increased Q-angle, the angle formed by the hip and the patellar tendon; a larger angle increases the lateral pull on the kneecap. Repetitive microtrauma from high-impact activities like running or jumping can also contribute by overwhelming the joint’s stabilizing mechanisms.
Non-Surgical Management and Recovery
The initial approach to managing patellar tracking disorder is conservative, focusing on reducing pain and restoring proper biomechanics through physical therapy. The primary goal is to correct the muscular imbalances that allow for lateral maltracking. This involves a dedicated strengthening regimen for the VMO to help balance the forces pulling on the kneecap.
Strengthening the hip abductor and external rotator muscles is also a fundamental part of recovery, as weakness in the gluteal muscles can cause the thigh to rotate inward, subsequently increasing the strain on the patellofemoral joint. Simultaneously, tight structures that are pulling the patella laterally must be stretched, including the hamstring muscles, the hip flexors, and the iliotibial band. This combined approach aims to create a muscular environment where the patella can track centrally and smoothly.
In addition to exercise, conservative treatments often incorporate temporary measures to alleviate symptoms. Rest, ice, compression, and elevation (RICE) are used to manage pain and inflammation, particularly after activity. Non-steroidal anti-inflammatory drugs (NSAIDs) can also be used temporarily to help reduce discomfort and swelling within the joint.
Bracing and Taping
Bracing and taping techniques offer immediate mechanical support. For instance, McConnell taping applies a specific pull on the kneecap to prevent lateral deviation during movement. These external supports are particularly helpful during the early stages of rehabilitation as the stabilizing muscles are being strengthened.