Background When Kellgren and Lawrence proposed their radiologic scoring method to assess OA in 1957, they introduced a grade 1 for doubtful OA, besides the grade 0 for no OA. How to use and consider this grade has been widely discussed. Is a joint at a KL 1 grade a pre-radiographic OA? Is KL 1 the first step to OA? These questions remain an opened issue since no one has looked at what happens to a KL1 joint over time.
Objectives To assess what becomes a KL1 joint in hand OA patients over 2.6 years.
Methods Data came from an international 3-year, randomized, placebo-controlled phase III trial designed to assess the effect of strontium ranelate compared to placebo on the radiographic progression of knee OA which included symptomatic primary knee OA patients (ACR criteria) at a Kellgren-Lawrence (KL) grade II or III, with a minimal joint space width (JSW) between 2.5-5 mm. Baseline and final postero-anterior radiographs of each hand were performed. Hand symptoms were assessed using the functional index for Hand OA (FIHOA; range 0-30) and the AUSCAN-function (0-900 normalized at 100). Two independent readers scored half of the pairs of radiographs obtained each, blinded to treatment and time sequence, using the KL (range 0-128 for the 32 joints graded), Kallman (0-204) and Verbruggen anatomical phase (0-218) scoring methods with a good inter-rater reproducibility (ICCs >0.8) Hand OA was established if at least 2 joints were scored ≥ KL 2. All the joints scored grade 1 according to KL scoring method identified at baseline were re-assessed on the final hand radiograph. Their evolution over time is described.
Results Of 1669 patients included in the SEKOIA trial, 1360 had hand radiographs. 999 (73%) had radiologic hand OA at baseline. 297 patients out of 472 in the placebo group had baseline and post-baseline radiographs. 71% were female, mean age 64±7 years, body mass index 29.6±5 kg/m², and initial knee JSW 3.5±0.8 mm. Baseline hand OA radiologic severity was mild: KL score 21.3±13, Kallman score 24.6±22 and Verbruggen score 13.7±15. The level of symptoms was low: FIHOA score was 4±5, Auscan global score was 31.8±28. Mean time interval between baseline and final radiographs was 2.6 years. 1203 joints were scored KL 1 at baseline (mean: 4.1±2.4 per patient). On final radiographs, 42 (4%) were scored KL 0, 779 (65%) remained KL 1, 356 (30%) were scored KL 2, 15 (1%) KL 3 and 6 (0.5%) KL 4.
Conclusions In this sample of knee OA patients with mild radiographic hand OA, 32% of the joints at a KL 1 grade progressed to a grade 2 or more, therefore became OA joints, when only 4% evolved to a grade 0 (no OA) after 2.6 years. KL 1 grade appears indeed to be the first step of a radiographic OA in many cases.
Disclosure of Interest E. Maheu: None Declared, C. Cadet Grant/research support from: Servier, F. Carrat: None Declared, Y. Barthe: None Declared, F. Berenbaum Grant/research support from: Servier