Study explores relationship between trochlear morphology, patellofemoral alignment and OA
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Extreme sulcus angle, greater patellofemoral index and patella displacement were associated with higher prevalent radiographic patellofemoral osteoarthritis, according to published results.
From September 2014 to September 2018, researchers from the department of orthopedics at Peking University in Beijing analyzed 451 patients (mean age 65.2 years, 66.8% were women) with unilateral radiographic patellofemoral osteoarthritis (PFOA). The cohort, which was comprised of residents from three rural towns in northern China, was assessed for radiographic PFOA, radiographic tibiofemoral OA, sulcus angle, patellofemoral index and patella displacement.
According to the study, researchers found a reverse J-shaped relationship between the sulcus angle and prevalent radiographic PFOA.
“Adjusted odds ratios of prevalent radiographic PFOA in the highest quarter of patellofemoral index and patella displacement were 4.69 and 3.60, respectively,” the researchers wrote in the study. “A similar relationship was observed between sulcus angle with either prevalent radiographic lateral or medial PFOA,” they wrote.
The researchers also concluded that greater values of patellofemoral index and patella displacement were associated with higher radiographic lateral (but not medial) PFOA. The results suggest “that anatomic structures indeed play a role in PFOA,” they wrote.
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Laurie Hiemstra, MD, PhD, FRCSC
These authors look at the prevalence and risk factors for patellofemoral osteoarthritis in a large Chinese population. They conducted a within person matched case-control study to study the relationship between trochlear morphology and patellofemoral alignment to radiographic evidence of patellofemoral osteoarthritis (PFOA).
These authors recognize that there is geographic and racial variation to PFOA and knee joint pathoanatomy. In rural China, in persons aged 50 years and older, there is a prevalence of unilateral PFOA of 11.3%. Women (66.8%) were affected more than men (33.2%), and lateral PFOA (90.5%) was more common than medial PFOA (9.5%).
Trochlear morphology, as measured by the sulcus angle, was statistically associated with lateral PFOA in that the subjects with the highest and lowest sulcus angles had the highest prevalence of PFOA. Given that the shape of the trochlea is unlikely to change once growth is completed, this is good evidence that trochlear shape does influence the development of OA changes in the patellofemoral joint.
Patellar alignment was associated statistically with lateral PFOA in that the more laterally shifted the patella, the higher the prevalence of lateral PFOA. Did the OA cause the lateral translation or did the lateral translation cause the OA? Is it the chicken or egg?
This study adds to our understanding of PFOA and the risk factors associated with it. Other anatomic factors such as patella alta, patellar tilt, femoral and tibial rotational abnormalities, and coronal plane malalignment need to be investigated in order to fully understand the etiology of PFOA.
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