Breaking the mould: A knee replacement that works around allergies

Knee replacement is today among the most routine surgeries in India. But not so for Dr Sunanda Gupta. Years of crippling arthritis had left the former Safdarjung Hospital professor struggling to walk. Yet, standard metal implants posed a serious risk as she was severely allergic to metals and multiple drugs, so much so that even jewellery and common painkillers triggered reactions. So, surgeons at AIIMS, Delhi opted for a fully ceramic, metal-free knee implant, underscoring how joint replacement is moving towards highly personalised solutions for select patients.Ceramic implants have been used safely in hip replacements for over two decades, but are still uncommon for knee surgery. Dr Gupta underwent the procedure in November 2025 and is now recovering well. She says the ceramic implant’s high biocompatibility and minimal tissue reaction made it the safest option for her, despite its high cost and limited availability. But her case is the exception, not the rule. Dr Vikrant Manhas, additional professor of orthopaedics at AIIMS, says completely metal-free ceramic knee implants are extremely rare and are reserved for patients who are unwilling or unable to opt even for hypoallergenic alternatives. “Most patients concerned about metal sensitivity can safely receive standard implants with special coatings that prevent direct tissue contact,” he explains, adding that only a small minority needs non-standard implants. Besides, ceramic knee implants can crack after a severe fall, though this risk has become uncommon with newer designs, while metal implants do not fracture.Cost is another major deterrent. Ceramic knee implants can be nearly twice as expensive as standard implants, making them impractical for routine use. “As coated metal implants work well for the vast majority of patients, ceramic knees are not commonly done in India,” Manhas says, describing the AIIMS procedure as necessity-driven rather than trend-setting.Scientific evidence, however, suggests ceramic knees can perform just as well — in the right patients. An eight-year prospective follow-up study published in 2024 in the Nature’s scientific report evaluated a completely metal-free ceramic knee implant used in total knee arthroplasty and found that outcomes were on a par with conventional metal knee implants in terms of function, patient satisfaction, activity levels and overall quality of life.No allergic reactions were reported in those who received ceramic implants, supporting their use in people with proven metal hypersensitivity. While gradual radiological changes were seen around the tibial component over time, these did not translate into clinical loosening or symptoms. Only one revision surgery occurred — due to trauma rather than implant failure. The study concluded that ceramic knee implants are a safe and effective long-term option for patients with metal allergy, provided proper surgical technique, especially full cementation of ceramic components, is followed.Amite Pankaj Aggarwal, principal director and head of orthopaedics and joint replacement at Fortis Hospital in Delhi’s Shalimar Bagh, says metal allergy to knee implants is rare but possible. Standard implants are typically cobalt-chromium alloys with trace nickel, the most common allergen. When allergy does occur, patients may develop persistent pain, stiffness, rashes or redness weeks to months after surgery and, in some cases, implant loosening that requires revision surgery.Patients with a history of skin reactions to jewellery or watches should inform their doctors, he advises. They are usually offered either alternative metals or cobalt-chromium implants coated with ceramic layers such as titanium nitride or zirconium oxide, which reduce metal ion release and wear and help extend implant life. Ceramic implants, he adds, are offered only to select patients. Experts also point out that the overall risk of metal allergy is negligible with modern implant materials. Aashish Chaudhry of Aakash Healthcare says advanced cobalt-chromium alloys and titanium nitride-coated implants — often referred to as gold-coated implants — are highly biocompatible and well tolerated, even in patients reporting metal sensitivity. He adds that ceramic remains standard for hips, not knees, where advanced metal alloys continue to be the proven choice.Doctors agree on one clear takeaway from the AIIMS case: ceramic knee implants are not meant for everyone, but can be life-changing for a tiny subset of patients. Dr Gupta’s experience highlights a shift from one-size-fits-all surgery towards implant choices tailored to a patient’s biology, risks and lifestyle, even when that path is rarer, costlier and more complex.