Osteophyte formation on medial wall of the intercondylar notch of femur is an early sign of osteoarthritic knee development using osteoarthritis initiative data

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Purpose: Reduction of incidence of osteoarthritic knee (KOA) is a big medical problem to be solved in this aged society. Development of disease-modifying OA drugs (DMOADs) has been pursued and knowledge about mechanisms leading to develop OA has been accumulating. But still there is no good solution for this. Thus, one practical alternative to achieve reducing incidence of OA would be earlier detection of pre-disease status, which will lead to find a new set of population that will respond early intervention. In our previous study using MRI data of osteoarthritis initiative (OAI), we identified osteophytes on the notch of femoral condyle was highly identified in population that were grade 0 or I on Kellgren and Lawrence scale (KL) at baseline and developed to more than grade II after 48 months. Characteristic of this osteophyte was that it could not be identified by conventional antero-posterior or lateral view of plain X-ray. In the study we did not refer to the laterality of the osteophyte formation; i.e., whether medial or lateral wall of the femoral notch the osteophytes were formed. To utilize the findings as early KOA biomarker, more detailed information should be sought. The purpose of this paper is to examine dominance of laterality in terms of osteophyte formation on notch of the femoral condyle as an early biomarker of KOA. Methods: MRI data: MRI data was earned from OAI version E.1. In all subjects, right knee was assessed. On version E.1., 2110 right knees were registered on baseline time (version 0.E.1.), and 1658 right knees were followed until 48 months after baseline time (version 5.E.1.). We extracted 66 knees meeting following criteria. 1) Kellgren and Lawrence grade 0 or 1 at base line, and 2) more than KL grade 2 at 48 months later. They were the same population used for our previous study. Assessment of osteophytes: MRI at baseline was assessed in terms of size and laterality (medial or lateral). For assessing osteophyte size, 8 point marginal osteophyte item of Whole-Organ Magnetic Resonance Imaging Score (WORMS) was employed. With this system, osteophytes were graded from 0 to 7 using the following scale: 0: none; 1: equivocal; 2: small; 3: small-moderate; 4: moderate; 5: moderate-large; 6: large; 7: very large. The laterality of location; i.e., medial or lateral wall of itercondylar notch was also recorded. Results: On the medial wall, 3, 6, 57 knees had grade 1, 2, and 3 osteophyte respectively. That meant 100 percent of the knee had medial side osteophyte. On the lateral wall, 5 and 6 knees had grade 1 and 2 respectively. There was no isolated lateral case so the all the lateral cases had osteophyte on medial wall as well. Conclusions: In this paper we elucidated that osteophyte formation on wall of the femoral condyle was much dominant on medial side than lateral side. Although we dealt with cross-sectional data, we speculated that osteophytes on the medial wall might precede lateral side. Biomarkers to detect early cartilage degeneration have been sought. Among them usefulness of MRI has been reported. But time and cost would be big problem to use it for screening purposes in actual clinical settings. Although additional work is necessary, we believe our finding might be a clue to develop screening system for early KOA. Because our data suggest that point of focus is detect single site osteophyte formation. This will be achieved by modifying x-ray technique or ultrasound.