Insufficiency fractures of the knee, ankle, and foot in rheumatoid arthritis: A case series and case-control study

OBJECTIVE: To evaluate cases of insufficiency fractures verified by magnetic resonance imaging (MRI) of the knee, ankle, and foot in patients with rheumatoid arthritis (RA) cared for in our clinic over an 8-year period, to identify possible risk factors, and to test these in a case-control study.

METHODS: All patients in the rheumatology clinic with RA were registered prospectively in the database, DANBIO. All MRIs ordered from the clinic were registered and coded according to the anatomical region. We were thus able to retrieve all patients with RA and performed an MRI of the knee or ankle/foot. The patients with fractures constituted the case series, and the patients without fractures constituted the control group.

RESULTS: The RA clinic population comprised 1,624 patients who underwent a total of 70 MRIs.

CASE SERIES: 39 insufficiency fractures were identified in 32 patients; 93% were women, and the median age was 68 years (range 33-89 years). Half of the patients had a T score >-2.5. The case control group without fractures comprised 38 patients; 74% were women, and the median age was 62 years (range 32-84 years). In the case series, 20 patients experienced later additional episodes of insufficiency fractures in the knee, ankle, or foot.

CONCLUSION: Insufficiency fractures of the knee, ankle, and foot are a significant cause of pain and long-lasting disability in RA. Recurrent fractures are common. Diagnosis is often delayed and confused with arthritic activity. Conventional radiography and DEXA scan are often normal. Older age, female gender, radiological erosions in hand/wrist, and treatment with methotrexate were all significantly associated with fractures.