Pain during prolonged sitting in subjects with patellofemoral pain in Dutch physical therapy clinics: an online questionnaire-based analysis.

Objectives: This study aimed to describe (1) differences between subjects with patellofemoral pain (PFP) with and without pain during prolonged sitting (PDPS), (2) minimum knee flexion angle and time to onset/disappearance of PDPS and (3) differences between those with PDPS at smaller/greater flexion angles and with fast/slow onset and disappearance of PDPS.

Design: Patient-reported online questionnaire.

Setting: Private physical therapy clinics in the Netherlands between May 2021 and March 2023.

Participants: 87 participants (61 (70%) females, mean age 22.0 years (IQR 4.0), body mass index 23.1 (4.7)).

Outcome measures: Visual Analogue Scale for worst pain (VAS-W) and sitting pain (VAS-W sitting), the Anterior Knee Pain Scale (AKPS), knee flexion angle to provoke PDPS and time to onset/disappearance of PDPS.

Results: 63 of 87 (72%) participants reported PDPS. Participants with PDPS experienced bilateral symptoms of PFP more frequently (71% vs 46%, p=0.44) and scored 12 points lower on the AKPS (p<0.001). Most participants (85%) reported a minimum knee flexion angle of ≥90°, median time to PDPS onset of 16-20 min and 6-10 min for disappearance. Participants experiencing PDPS at smaller flexion angles exhibited higher VAS-W and VAS-W sitting scores (7.0 (1.0), 6.8 (1.1)) than those at greater flexion angles (5.0 (3.0), for both) (p=0.002, p=0.001). Participants with fast onset of PDPS reported higher VAS-W and VAS-W sitting scores (7.0 (2.0), 6.0 (2.0)) than those with slow onset (5.0 (3.0), 5.0 (4.0)) (p<0.001, p=0.025).

Conclusions: Participants with PDPS reported higher levels of disability than those without. PDPS was typically induced at knee flexion of ≥90°, with delayed onset/disappearance. Higher pain levels were reported by those experiencing PDPS at smaller knee flexion angles or with faster onset. Future research should explore the mechanisms of PDPS and develop targeted interventions to improve long-term outcomes.