Cobalt Syndrome Following Total Knee Arthroplasty: A Case-Based Review and Clinical Implications

Cobalt syndrome, also known as metallosis or adverse local tissue reaction (ALTR), is characterised by local inflammation and systemic toxicity due to cobalt ion release from orthopaedic implants [1]. While primarily associated with metal-on-metal hip arthroplasty, polyethylene liner degradation in TKA has emerged as a potential source of cobalt exposure [2]. The Exactech Optetrak Logic system was globally recalled in 2022 due to packaging faults that accelerated polyethylene oxidation [3]. This degradation can lead to micromotion, edge loading, and unintended metal-on-metal contact, triggering cobalt and chromium ion release [4].

This report synthesises findings from a detailed independent medical examination conducted in September 2025 of a 58-year-old male patient who underwent bilateral TKA in June 2021. Data were extracted from surgical records, imaging, pathology reports, and manufacturer documentation. A literature review was conducted using PubMed, MDPI, and JAMA Network Open to identify relevant studies on cobaltism in arthroplasty.

Clinical Presentation: The patient developed persistent left knee pain, swelling, and synovitis 18 months post-TKA. Imaging revealed synovial inflammation without loosening. Aspiration ruled out infection. Systemic symptoms included fatigue, anxiety, impaired mobility, and suspected thyroid dysfunction (Table 1).

Implant Composition: 

Table 1: Degradation of polyethylene may lead to metal-on-metal contact between femoral and tibial components. 

Pathophysiological Cascade

Investigations and Management:

Physical examination revealed a warm, swollen left knee with limited flexion and instability. Imaging confirmed synovitis without loosening. Cobalt assays and thyroid function tests were performed. Revision surgery was planned, and interim management included multidisciplinary rehabilitation and pain care.

This case underscores the diagnostic complexity of cobalt syndrome in TKA. Although knee implants are not typically associated with metal-on-metal articulation, polyethylene degradation can result in unintended metal contact and ion release [5]. Studies show that 57% of patients with cobalt-chrome implants test cobalt-positive, with systemic symptoms such as fatigue and thyroid dysfunction [6]. The European Union’s classification of cobalt as a carcinogen highlights the need for long-term surveillance [7]. 

Hypoallergenic revision strategies have been described for metal allergy in knee arthroplasty [8]. Vigilant surveillance following device recalls, including metal ion quantification and targeted imaging, is crucial for early intervention [9].

Cobalt syndrome is a clinically significant but underrecognized complication of TKA. This case demonstrates the importance of early diagnosis and intervention, particularly in the context of recalled implants. Multidisciplinary care and surgical revision are essential for symptom resolution and functional recovery.

I want to acknowledge the law firm Commins Hendriks, located at 23 Gurwood Street, Wagga Wagga, NSW, Australia 2650, and the client who attended for an assessment for a medical negligence claim, who made it possible to further research and investigate this clinical disorder.

This research received no external funding.

The author declares no conflict of interest related to this manuscript.

This case report was prepared in accordance with ethical standards. Patient consent was obtained for publication.

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