Metallosis refers to the deposition of metallic wear particles in periprosthetic tissues, most commonly seen in metal-on-metal hip prostheses but less frequently in total knee replacement (TKR) ^[1,2]. It is associated with chronic inflammation, synovitis, and osteoclastic bone resorption, which may culminate in aseptic loosening of implants ^[3,4]. In TKR, metallosis may develop due to polyethylene liner wear or dissociation, failure of metal-backed components, or trauma leading to direct metal-on-metal articulation ^[5,6,7]. We present a case of severe metallosis-induced osteolysis and polyethylene liner dissociation causing failure of TKR, managed successfully with revision arthroplasty.

A 63-year-old female presented with pain, swelling, and reduced flexion in the right knee following a fall 2 months earlier. She also reported a 3-year history of recurrent instability, sudden locking, and restricted motion, which she occasionally relieved by self-manipulation. She had undergone bilateral TKR (left knee 15 years ago and right knee 12 years ago) using the Stryker Duracon system. At a local hospital, X-ray imaging, as shown in Figs. 1 and 2, revealed tibial component loosening, polyethylene liner dissociation, and marked osteolysis. Laboratory parameters (complete blood count, erythrocyte sedimentation rate, and C-reactive protein) were normal, excluding infection.

Figure 1: There is osteolysis, dislocation, and implant loosening in the right knee, whereas the left knee appears normal in anteroposterior X-ray.

Figure 2: Dislocation is well noted in the lateral right knee X-ray, whereas the left knee appears normal.

On admission to our center, she had persistent swelling and pain with restricted mobility. A one-stage revision TKR was performed, involving implant removal, extensive synovectomy, and reconstruction with a constrained modular revision system. Intraoperative images, as per Fig. 3, show metallic debris and a worn-out polyethylene liner, which gives us a diagnosis of metallosis. Post-operative radiographs confirmed stable implants without evidence of loosening, as shown in Fig. 4.

Figure 3: Metallic debris, a worn-out polyethylene liner, gives us a diagnosis of metallosis.

Figure 4: Post-operative X-ray following revision total knee replacement of the right knee.

At follow-up, the patient reported resolution of pain and improved mobility, with no recurrence of instability.

Metallosis results from the accumulation of metallic wear debris within periprosthetic tissues, triggering a chronic inflammatory cascade mediated by cytokines such as interleukin (IL-1), IL-6, IL-8, and tumor necrosis factor-α ^[3,8]. This immune reaction promotes synovitis, osteolysis, and progressive implant loosening. Although crepitus is a hallmark of hip prostheses, it is rarely described in knees ^[3]. In TKR, common etiologies include polyethylene liner wear, dissociation, or patellar component failure ^[6,7]. Rader et al. observed metallosis in 7 of 30 cases with metal-backed patellae, and more than half also showed liner dissociation ^[6]. In our case, tibial liner dissociation led to direct metal-on-metal contact, accelerating wear and osteolysis. Management requires revision arthroplasty combined with meticulous synovectomy, since conservative measures are ineffective ^[9]. Alternative prosthetic materials, such as oxinium, have been introduced to reduce metallic ion release and limit hypersensitivity reactions ^[10]. Our case reinforces the importance of vigilance even years after primary arthroplasty, as delayed metallosis-related osteolysis can compromise outcomes ^[4,11,12,13].

Severe metallosis following TKR is uncommon but can cause rapid osteolysis and catastrophic implant failure. Long-term surveillance of TKR patients is essential. Revision with thorough synovectomy and prosthetic replacement remains the definitive management.

Metallosis should be suspected in patients with late-onset pain, instability, and swelling after TKR. Revision surgery is the only effective treatment to prevent further destruction and restore function.