Patellofemoral pain is a common complaint especially in young adults. It can be caused by patellar maltracking. Part of this is a patella alta. When patellar maltracking is the cause of the problem and conservative therapy fails, surgery, a tibial tuberosity transposition, may be considered. Most research has been done in patients with recurrent patella luxation. However, in patients without luxation, research is scarce.

It is known that patients with patella alta have an increased risk of developing patellofemoral chondropathy due to increased pressure. With this study, we aim to investigate whether and how a tibial tuberosity transposition in patients with patella alta and no instability affects the degree of patellofemoral chondropathy and patient satisfaction after 10 years. This will allow us to educate patients regarding long-term outcomes better.

Anterior knee pain is a common complaint, especially in younger and active adults. An obvious source for anterior knee pain is patellar maltracking, which is often associated with patella alta (a high-riding patella). Due to maltracking, the cartilage of the patella can face a greater amount of pressure, which can cause cartilage damage. When conservative treatment fails, a surgical intervention can be considered. One of the surgical options is performing a tibial tubercle transfer (TTT), where the patella is being distalized and medialized. As a result, the improvement in patellar tracking will reduce the pressure on the retropatellar cartilage. The TTT has been proven effective in patients with patellar instability but less is known about patients without instability. Specifically, whether these patients face a higher risk of developing retropatellar cartilage damage ('retropatellar chondropathy') due to this intervention is currently unknown.

The primary aim of this study is to determine the incidence and the degree of retropatellar chondropathy 10 years after a TTT in patients with anterior knee pain without patellar instability. The secondary aim is to evaluate the long-term patient reported outcomes (PROMs) 10 years after a TTT in patients with anterior knee pain without patellar instability.

Inclusion Criteria:

• Age between 18 and 80 years
• Participated in an earlier cohort study
• Underwent a tibial tubercle transposition between 2012 and 2015
• Preoperative MRI available

Exclusion Criteria:

• No preoperative MRI is available
• Patellar-related surgery after the initial surgery
• Female patients that are (expecting to be) pregnant

Patients whom around 10 years ago presented with anterior knee pain and patella maltracking without instability, where conservative therapy failed and a TTT was performed, and who participated in the original cohort.