Detection of Pain Severity with the Full Cup Test in Knee Osteoarthritis and Its Relationship with Knee Function and Quality of Life

Objective: The aim of this study was to evaluate pain severity using the Full Cup Test (FCT) in patients with knee osteoarthritis (OA) and its relationship with knee function and quality of life. Methods: This multicenter, prospective, cross-sectional study was conducted between July 2024 and October 2024. Ethical approval was obtained from the University Non-Invasive Clinical Research Ethics Committee prior to the commencement of the study (2024-GOKAEK-248_105). All patients’ demographic characteristics, general health data, and Kellgren-Lawrence staging were recorded. The following assessments were administered to all patients: the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) for evaluating knee pain and functionality; the Visual Analog Scale (VAS) and FCT for pain intensity at rest, and during movement; and the Short Form-36 (SF-36) for quality of life. Results: A total of 108 participants (90% female; mean age: 57 years) were included. The majority were housewives, and approximately 25% were illiterate. FCT-rest scores demonstrated a strong correlation with VAS-rest and a weak negative correlation with the SF-36 bodily pain, vitality, and social functioning (SF) subscales (P < 0.01). FCT-motion scores were strongly correlated with VAS-motion, moderately positively correlated with WOMAC pain, stiffness, and total scores, and negatively correlated with SF-36 bodily pain, general health, mental health, and SF. Conclusion: To our knowledge, this is the first study in the literature evaluating the utility of FCT in knee OA. FCT was found to be a valid, simple, and comprehensible tool for assessing pain in patients with knee OA. The results also demonstrated a meaningful association between FCT and both functional status and quality of life, indicating its broader clinical utility. Given its ease of use, FCT may be particularly beneficial in routine clinical practice, especially among elderly individuals and those with low educational attainment or cognitive decline.