Impact of ultrasonography detected quadriceps calcific tendinopathy on pain and function in patients with primary knee osteoarthritis

Calcific tendinopathy is most commonly seen around the shoulder joint. Only a few cases of quadriceps calcific tendinopathy (QCT) were reported. This study compares pain, function, clinical examination results, and ultrasonographic findings among primary knee osteoarthritis (KOA) patients with or without ultrasonography-detected QCT. A cross-sectional study was conducted on 214 patients with knee OA. Ultrasonography (US) of knee joints was performed according to the EULAR guidelines. Kellgren-Lawrence radiographic grading was used to score OA. Pain and functional status were assessed using the visual analog scale (VAS), the Health Assessment Questionnaire-II (HAQ-II), and the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC). QCT was detected in 50 out of 428 knees (11.6%), i.e. in 46 out of 214 patients (21.49%). Most cases of QCT were detected in the following sites: 36 in the vastus lateralis (72%), 10 in the vastus intermedius (20%), and only 4 in the vastus medialis (8%). QCT was found mainly in advanced KOA stages: 44 cases of QCT were found in patients with grade 4 KOA and 6 cases in grade 3 KOA. The presence of QCT showed a statistically significant association (p