Hidden osteophyte formation on plain X-ray is the predictive factor for development of knee osteoarthritis after 48 months--data from the Osteoarthritis Initiative.

OBJECTIVE

To examine whether the detection of osteophytes anywhere in the knee could serve as a pre-radiographic biomarker for osteoarthritis (OA) development.

METHODS

Baseline magnetic resonance imaging (MRIs) of 132 participants in the Osteoarthritis Initiative (OAI) were studied. Based on radiographs, 66 knees were assessed as osteoarthritis-free (no-osteoarthritis [NOA], or Kellgren/Lawrence [K/L] severity grade 0/1 both at baseline and 48 months), and another 66 knees were assessed as having radiographic OA changes (pre-radiographic osteoarthritis [PROA], or with K/L grade 0/1 at baseline and grade ≥ 2 at 48 months). Using baseline MRI data, we examined eight sites of osteophyte formation: the medial and lateral femoral condyle (MFC and LFC, respectively); medial and lateral tibial plateau (MTP and LTP, respectively); medial and lateral facets of the patellofemoral joint (PM and PL, respectively); tibial spine (TS); and femoral intercondylar notch (IC). Knee joint osteophyte size was assessed via the 8-point marginal osteophytes item of the whole-organ magnetic resonance imaging score (WORMS). The frequencies and distributions of osteophytes were compared between groups.

RESULTS

Mild-size osteophytes (defined as score ≥ 2) were observed more frequently at the MFC (P = 0.00278), MTP (P = 0.0046), TS (P = 0.0146), PM (P < 0.0001), PL (P = 0.0012), and IC (P < 0.0001) in PROA knees than in NOA knees. Moderate-size osteophytes (defined as score ≥ 4) were more frequently observed in PROA knees than in NOA knees only at the IC (P < 0.0001).

CONCLUSION

Knees with osteophyte formation at the IC, even those of K/L severity grade 0/1, are at risk for the development of radiographic OA by 48 months.