Physical exam findings of patellofemoral grind may help predict which patients with knee osteoarthritis (OA) are likely to experience significant worsening of their disease, according to analysis of data from the Osteoarthritis Initiative and published in Arthritis Care & Research.
Individuals with persistent patellofemoral grind had a greater annual loss of cartilage volume compared with those without this clinical finding (1.30% vs 0.90%, PP=0.002), the researchers note, in a media release from MedPage Today.

Two tests that are routinely performed to evaluate knee abnormalities are the joint line tenderness test and the patellofemoral grind test. Joint line tenderness is typically assessed by palpation of the medial and lateral tibiofemoral joint line to diagnose meniscal pathology, which can be present before the onset of OA.

The patellofemoral grind test combines external compression on the patella while the patient actively contracts the quadriceps muscle, and a positive result indicates the presence of patellofemoral pathology.

To explore the possibility that these tests could be useful predictors of OA progression, Wang’s group analyzed outcomes of patients enrolled in the National Institutes of Health’s OA Initiative, which is the largest observational cohort of knee OA patients.

Knee cartilage volume was evaluated with MRI, and worsening of radiographic OA was defined as an increase in the Kellgren-Lawrence grade by year 4.

The analyses were adjusted for sex, age, body mass index, and pain scores on the Western Ontario and McMaster Universities (WOMAC) scale.

A total of 4,353 patients were included. At baseline, 51.4% had radiographic OA, 35% had joint line tenderness, and 15.8% had patellofemoral grind. Mean age was 61, and 58% were women, the release explains.

Unlike patellofemoral grind, three was no association between the presence of joint line tenderness at baseline or at 1 year and cartilage volume loss.

In contrast, a positive test for patellofemoral grind at baseline was associated with a significant elevation in risk for total knee replacement (OR 1.55, 95% CI 1.11-2.17, P=0.01). This association also was significant for both fluctuating and persistent symptoms.

However, there was no association between baseline patellofemoral grind and worsening of radiographic OA (OR 1.06, 95% CI 0.80-1.41), or between persistent or fluctuating patellofemoral grind and worsening of radiographic OA. The finding that patellofemoral grind was associated with loss of articular cartilage and risk of total knee replacement but not with progression of radiographic OA suggests that increases in Kellgren-Lawrence grades result from different processes such as the development of osteophytosis, the researchers explained.

Similar findings were seen on a subgroup analysis of patients who had radiographic OA at baseline. In this group, the presence of baseline patellofemoral grind was associated with an elevated risk for total knee replacement (OR 1.60, 95% CI 1.14-2.24, P=0.006). The association was significant for both fluctuating (OR 1.59, 95% CI 1.09-2.31, P=0.02) and persistent (OR 2.15, 95% CI 1.33-3.48, P=0.002) symptoms, the release continues.

“These data suggest that patellofemoral grind may represent a clinical marker associated with adverse long-term joint outcomes and thus may be used to help identify individuals at risk of disease progression, regardless of the severity of radiographic OA or the levels of self-reported knee pain,” Wang and colleagues write.

Because the management of knee OA initially relies on conservative measures such as weight loss and exercise that require patient motivation and participation, identifying these patients could help with adherence to treatment guidelines, they conclude, per the release.

A limitation of the study was its lack of adjustment for the use of medications by patients.

[Source: MedPage Today]