High prevalence of contralateral ankle abnormalities in association with knee osteoarthritis and malalignment

Abstract

Objective: To evaluate ankle joint abnormalities in a knee osteoarthritis (OA) cohort.

Methods: Participants (n = 159) with symptomatic and radiographic OA in at least one knee underwent technetium-99m methylene diphosphonate bone scan (scored 0-3) of the ankles and forefeet. Knee radiographs were graded for OA features of joint space narrowing (JSN) and osteophyte (OST). Ankle symptoms and history of ankle injury were assessed by self-report. Knee alignment was measured from a long-limb radiograph. Ankle radiographs were obtained on those who returned for follow-up (n = 138) and were graded for ankle tibiotalar JSN and OST.

Design: Ankle scintigraphic abnormalities were frequent (31% of individuals, one-third bilateral). Ankle symptoms were reported by 23% of individuals and history of ankle injury by 24%. Controlling for gender, age, body mass index (BMI), and contralateral predictor, ankle scintigraphic abnormalities were associated with: ipsilateral ankle symptoms (P = 0.005); contralateral knee JSN (P = 0.001), knee OST (P = 0.006) and knee malalignment (P = 0.08); and history of ankle injury or surgery of either ankle (P < 0.0001). At follow-up, scintigraphic abnormalities of the ankle were strongly associated with presence of tibiotalar radiographic OA (P < 0.0001).

Conclusions: Although considered rare, we observed a high prevalence of radiographic features of ankle OA in this knee OA cohort. History of overt ankle injury did not appear to account for the majority of ankle abnormalities. These results are consistent with a probable kinematic association of knee OA pathology and contralateral ankle abnormalities and suggest that interventions targeting mechanical factors may be needed to prevent ankle OA in the setting of knee OA.

Keywords: Alignment; Ankle; Knee; Osteoarthritis; Scintigraphy.

Figure 1. Ankle scintigraphic images

Representative late phase technetium-99m–disphosphonate bone scintigraphic images of ankle joints depicting the various and distinct patterns of uptake. Shown are anteroposterior views (top row) and mediolateral views (bottom row). These images illustrate examples of uptake in a) normal joint, b) medial ankle and forefoot, c) lateral ankle and forefoot, d) forefoot only, and e) generalized medial and lateral ankle and forefoot.

Figure 2. Frequency and localization of scintigraphic abnormalities in the ankle

A total of 318 ankle joints were scored for intensity of scintigraphic uptake based on a four-point scale (0=none, 1=mild, 2=moderate, 3=intense uptake) by compartment (medial or lateral) and bone site (talar and/or tibial). A total of 108 sites in 70 ankles had abnormal scintigraphic uptake (score >1). The frequency of bone scan uptake for each level of intensity (0–3) is depicted as a % for each site.