• Some anatomical patterns accelerate patellofemoral cartilage degeneration in patients with OA.
• These metrics could flag patients who might benefit from early non-surgical intervention/prevention.

Elevated tibial tubercle-trochlear groove, external tibiofemoral rotation and entry point-transition point angle may be associated with cartilage damage progression in lateral patellofemoral osteoarthritis, according to results.

“All three metrics essentially tell a similar story. If the patella or the extensor apparatus is lateralized, you might have higher forces — more localized forces, higher peak stresses — which could lead to the accelerated cartilage damage progression trend we observe,” Johannes M. Sieberer, MS, a graduate student in Yale School of Medicine’s patellofemoral research program, told Healio. “This is still a correlational study, but we are fairly confident that lateral overload leads to that progression. These metrics give us indication if lateral overload is there or not.”

Using non-weight-bearing CT scans from a subset of 389 knees in the Multicenter Osteoarthritis Study, Sieberer and colleagues used the MRI Osteoarthritis Knee Score (MOAKS) to analyze MRI scans of the knee for progressive patellofemoral cartilage damage at baseline and 2 years. Researchers also measured tibial tubercle-trochlear groove (TT-TG) distance, patellar tilt, external tibiofemoral rotation, patellar height, entry point-trochlear groove angle and entry point-transition point angle in each knee.

The dataset included an equal number of patients showing progressive patellofemoral cartilage damage and patients showing no increased damage during a 2-year period, with damage defined as an escalation of at least a half grade according to MOAKS.

Sieberer and colleagues found 58 trochleae and 16 patellae had worsening lateral patellofemoral cartilage damage, and four participants showed progressive degeneration in both the patella and femur.

Logistics regression models showed patients with relative external tibiofemoral rotation were 27.1% more likely to experience progressive patellofemoral cartilage damage per 4.89°, while patients with higher TT-TG were 25.9% more likely to experience progressive patellofemoral cartilage damage per 3.7 mm. Researchers found a significant association between lateral patellar tracking and rotational malalignments with patellofemoral cartilage damage.

Sieberer told Healio early identification of these anatomic patterns could serve as a preventive tool for patients with early-stage OA and patellar instability who may benefit from nonsurgical treatments, including lifestyle changes.

“[Patients with increased TT-TG distance or entry point-transition point angle] are likely candidates who will have problems down the line,” Sieberer said. “They might need a knee replacement, but we might be able to delay it a couple of decades.”

Johannes M. Sieberer, MS, can be contacted at johannes.sieberer@yale.edu.