Marcri and colleagues evaluated the effect of trochlear morphology and patellofemoral (PF) alignment on anterior knee pain in their study, “Relation of patellofemoral joint alignment, morphology, and radiographic osteoarthritis to frequent anterior knee pain: The MOST Study.” They obtained imaging from the multicenter osteoarthritis study (MOST) cohort and used two data analysis approaches: a within-person knee-matched evaluation of 110 patients aged 50 to 79 years with unilateral anterior knee pain (AKP) (conditional logistic regression); and a cohort approach comparing 58 patients with AKP to those 824 (again ages 50 to 79 years) without frequent AKP (binomial regression).
They did not find a relationship between AKP and trochlear morphology, patellar alignment or tibiofemoral (TF) osteoarthritis (OA). This did show a positive relationship between patellofemoral OA and AKP. From a clinical perspective, I agree that nonarthritic trochlear dysplasia and TF OA are not associated with AKP and PF OA is associated with AKP. Trochlear dysplasia is associated with patellar instability in the younger patient and is associated with future PF OA risk.
On the other hand, the finding that patellofemoral “malalignment” is not associated with AKP is counterintuitive to what many PF specialists would offer. Many factors could contribute to this discrepancy.
1) AKP outside of PF OA is most often encountered in those younger than 50 years and study patients were 50 to 79 years.
2) Seventy-nine-year-old patients often have general health conditions that lead to more sedentary activities than the younger population. That is, they may not use stairs or steps as frequently and may not load the PF compartment sufficiently to tease out the differences between normal and malalignment. Even advanced PF OA patients do acceptably well on level ground.
3) We do not know the genetics of the patients. Some patients with “poor cartilage genetics” and patellar malalignment often present with PF OA in the age group of 40 to 60 years. Thus, those patients would have crossed over to PF OA cohort before inclusion in the study.
I agree with the authors that a larger study is warranted and would add patients of all ages.
Jack Farr, MD
Knee preservation and cartilage restoration,
Disclosures: Farr reports no relevant financial disclosures.