Background Patella alta is the malalignment of the patella in the vertical plane. There are a number of studies that confirmed the relation of patella alta and patellofemoral knee osteoarthritis (OA). Nevertheless, to our knowledge, none has studied the possible relationship between patella alta and tibiofemoral knee OA.
Objectives The objectives of the current study were i) to determine the prevalence of patella alta among patients with radiographic tibiofemoral knee OA and ii) to evaluate whether the frequency of patella alta differs by the severity of knee OA.
Methods Patients who had undergone X-ray examination of the knee with a diagnosis of knee OA between January 2013-February 2016 were included in the study. Following the application of the exclusion criteria, remaining patients' radiographs were graded according to the Kellgren Lawrence grading system. Knees were divided into mild OA (KL grade 1–2) and severe OA (KL grade 3–4) groups. Computerized measurement of the craniocaudal patellar distance (CPD) and the patellar tendon length (PTL) was performed on lateral knee radiographs. According to the Insall-Salvati method, the PTL/CPD ratio >1.2 was regarded as “patella alta”. The overall prevalence of patella alta was determined. The rate of patella alta was compared between mild and severe OA groups.
Results A total of 712 radiographs were assessed for eligibility. Measurements were performed on 416 lateral knee radiographs belonging to 253 patients with a mean age of 62.7±11.3 years. The prevalence of patella alta in the whole group was 9.1%. The frequency of patella alta was significantly higher in the severe OA group when compared with the mild OA group (p<0.001).
Conclusions According to the results of the present study, patella alta appears to be associated with increased severity of radiographic tibiofemoral knee OA. “High riding” patella should be kept in mind as a determinant of disease severity in patients with knee OA.
Disclosure of Interest None declared