Heberden’s nodes (HN) and Bouchard’s nodes (BN) are firm swellings over the superolateral and dorsal aspects of distal and proximal interphalangeal joints respectively.^1,2 Despite their prevalence the pathogenesis of nodes remains unclear, although bony outgrowth³ and endochondral ossification of marginal hypertrophic fibrocartilage^4,5 are implicated in their aetiology. Nevertheless, it is widely held that nodes are associated with hand osteoarthritis (OA),^5–,⁷ that they are a marker for systemic predisposition to generalised OA,^6,7 and that they reflect the presence of underlying osteophyte (OST).^4,5 However, the link between HN and underlying interphalangeal OA has been questioned in one study of middle-aged female twins,⁸ in which a poor correlation was found between HN and underlying radiographic OST, assessed on a 0–3 scale using a radiographic atlas.⁹ In contrast, a more recent study¹⁰ of 71 subjects with hand OA showed a reasonable correlation between HN and radiographic OA in the corresponding joint, assessed using the global Kellgren and Lawrence scale.¹¹ Thus the postulated association between nodes and underlying OA is in doubt.

We therefore undertook a cross sectional study of women and men with HN to determine whether nodes are associated with radiographic OA of the corresponding joint. Unlike previous studies^8,10 we assessed individual radiographic features of OST and joint space narrowing (JSN) and investigated the influence of sex, age, and body mass index (BMI) on the relationship.

METHODS

RESULTS

DISCUSSION

This study shows that in a mixed population of men and women with a broad age range, digital nodes are associated with underlying radiographic changes of interphalangeal OA, as suggested previously.⁴ This association is stronger for OST and is not significantly influenced by sex, age, or BMI.

The higher OR observed between HN or BN and OST suggests that the main association is with OST. Interestingly, more marked HN (grade = 2) with dorsolateral swelling on both radial and ulnar aspects were a better predictor of JSN than unilateral swellings, but this was not so for OST (table 2⇑). Because nodes evolve slowly to reach their maximum size, this suggests that radiographic JSN manifests later in the course of node development and that established nodes affecting both aspects of the joint are a good clinical marker for this change. However, a prospective study is required to confirm this. The stronger relationships between nodes and radiographic changes seen at DIP joints might be explained anatomically. The presence of lateral bands over proximal interphalangeal joints may influence osteophyte growth making it less distinct than at DIP joints.

The different conclusions from our study and those of Cicuttini et al⁸ may be accounted for in part by the populations studied. Cicuttini et al studied middle-aged female twins with a mean age of 56 years, whereas we studied both women and men with a mean age of 66 years. Such a demographic difference might result in our population having more patients with fully established nodes. If nodes do form by endochondral ossification then a temporal difference might be expected, in that new (radiolucent) fibrocartilage might form a palpable swelling some time before calcification and ossification make it apparent on radiographs.

There are several caveats to this study. Firstly, index patients were recruited through hospital referral with symptomatic OA and their relatives were recruited subsequently. It was not a random population sample and thus is subject to selection bias. Secondly, it was cross sectional; only a prospective study can document the temporal relationship between nodes and OA changes. Thirdly, nodes were scored clinically and OA changes examined by radiographs using a single view. Although reproducibility for nodes was good the reproducibility for radiographic scores varied according to joint site and might have influenced the results. Furthermore, a single dorsal-palmar radiograph might be expected to be sensitive for lateral but not dorsal OST. In future studies, it would be preferable to employ more sensitive imaging such as magnetic resonance imaging or high resolution ultrasound to assess both joint and periarticular tissues in more than one plane. Indeed, the results of a recent magnetic resonance imaging study of patients with HN¹⁵ show consistent and prominent abnormalities of collateral ligaments in affected DIP joints, with more variable abnormalities of all other joint structures, thus emphasising the importance of non-cartilage tissues in pathogenesis.

In conclusion we have demonstrated a positive relationship between HN, BN, and underlying radiographic change. This association is stronger for OST, suggesting that nodes do appear to be linked pathologically to changes in underlying joints. These findings may have implications for genetic studies of hand OA in suggesting that the presence of HN and BN may be taken as clinical markers of predisposition to underlying interphalangeal OA.