Bone Metabolic Activity in the Patellofemoral Joint in Patients With Unilateral PFP

Patellofemoral pain (PFP) is a highly prevalent musculoskeletal condition mainly affecting younger people, causing pain, physical disability, and reduced quality of life. The cause of PFP is still unknown. It is, i.e., unclear whether there is a link between PFP and changes in the cartilaginous (subchondral) bone in the joint between the patella and the femur. Our goals are to use 18F NaF PET/CT to evaluate whether subjects with unilateral patellofemoral pain exhibit elevated bone metabolic activity in the painful knee compared to the pain free knee and to determine whether bone metabolic activity correlates with pain intensity and location of pain. Furthermore, we aim to investigate the effects of acute loading on the bone metabolic activity. The primary objective of this cross-sectional study is to assess whether patients with unilateral PFP have increased bone metabolic activity in the painful knee compared to the pain free knee. We will assess quantitative parameters indicative of bone metabolic activity (Standardized Uptake Value (SUV) and kinetic data) and compare values between the painful knee and the pain free knee. The secondary objectives are to 1) determine whether a bout of single leg weight bearing knee bends standing on a wedge result in increased bone metabolic activity acutely in the painful knee compared to the pain free knee, and 2) identify "hot" regions of abnormal tracer uptake and compare area and SUV values between the painful knee and the pain free knee. An explorative objective is to determine the correlation between bone metabolic activity and pain intensity and location of pain.