Knee Implants — What Actually Differs Between Them
Patients are often handed a brand name and a price, and left to guess what separates one implant from another. This page explains the real variables — components, bearing materials, how the implant is anchored to bone, cruciate-retaining versus substituting designs, and what robotic-arm assistance does and does not do. It also explains why implants are charged separately from the hospital package, which is the single fact that makes two quotes hard to compare. See the package charges page for the underlying schedule.
What a knee replacement implant is actually made of
A total knee replacement is not one object. It is three or four components that together resurface the worn joint. Gujarati: ghutan nu implant — Hindi: ghutne ka implant.
- Femoral component — a curved metal shell that caps the end of the thigh bone and recreates the rolling surface the knee bends on.
- Tibial component — a metal tray fixed to the prepared top of the shin bone, usually with a short keel or stem into the bone.
- Polyethylene insert — the bearing that sits between the two metal parts. This is the surface that experiences wear, and it is the part most affected by material science.
- Patellar button — a polyethylene resurfacing of the back of the kneecap, used in some cases and not others.
A partial (unicompartmental) replacement resurfaces only one side of the knee using smaller versions of the same components — but it needs the remaining compartments and the cruciate ligaments to be sound, confirmed on imaging and at surgery.
Four things that genuinely differ between implants
Source: B. Shah Mahavir Super Speciality Hospital, Schedule of Charges (2024 revision), package rates. Rates are reviewed periodically — the figure applicable to you is confirmed at consultation. Implants are charged separately.
| Variable | The options | What decides it for you |
|---|---|---|
| Materials | Cobalt-chromium or titanium alloy for the metal components; oxidised zirconium on some femoral components; conventional, highly cross-linked or vitamin-E stabilised polyethylene for the bearing insert. | Metal sensitivity history, expected demand on the bearing, and the surgeon's assessment of your bone and soft tissue. |
| Fixation | Cemented — anchored with bone cement (PMMA) for immediate stability. Cementless — a porous or textured surface into which your own bone grows over subsequent weeks. Hybrid combinations exist. | Bone quality above all. Cemented remains the most widely used approach and is generally preferred where bone is osteoporotic; cementless needs good bone stock to achieve ingrowth. |
| Design philosophy | Cruciate-retaining (CR) keeps your posterior cruciate ligament. Posterior-stabilised (PS) removes it and substitutes mechanically with a post-and-cam. Others include medial-pivot and mobile-bearing designs. | Whether your posterior cruciate ligament is intact and competent, the degree of deformity, and the ligament balance achieved at surgery. Often finalised on the table. |
| Sizing range | Number of femoral and tibial sizes offered, and whether left and right or narrow variants exist to match different anatomies. | Your anatomy. A wider size range simply gives more chance of a close fit, which matters more in smaller-framed patients. |
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What none of these settles. No implant variable on its own predicts how your knee will feel. Alignment, ligament balance, surgical technique and — enormously — your rehabilitation all matter. Choosing a more expensive implant does not substitute for any of them.
The names you are most likely to hear
Several manufacturers produce well-established, regulator-approved knee systems used in large numbers worldwide — Stryker, Zimmer Biomet, DePuy Synthes and Smith+Nephew among them. Three are described here because they are the ones patients in Surat ask about most.
Stryker — including Mako robotic-arm assisted surgery
Stryker's knee portfolio includes the widely used Triathlon total knee system, available in cruciate-retaining and posterior-stabilised configurations and in cemented and cementless fixation. Stryker also makes Mako, the robotic-arm assisted platform used for total and partial knee replacement and for hip replacement.
A Mako robotic system is available at Mahavir Hospital, where Dr. Khanna operates. Whether it is used in your case is a surgical judgement, discussed at consultation.
Zimmer Biomet Persona
Persona is Zimmer Biomet's total knee platform, built around a wide range of femoral, tibial and articular-surface options so that components can be matched more closely to individual anatomy. It is offered in cruciate-retaining, posterior-stabilised and other bearing configurations, with cemented and cementless fixation options.
Zimmer Biomet also produces its own robotic platform, ROSA Knee, used with the same implant family.
Arthrex — arthroscopy and sports implants
Arthrex sits in a different category. Its best-known products are not joint replacements but the fixation devices used in keyhole surgery: suture anchors for rotator cuff and labral repair, cortical suspensory buttons and interference screws for ACL graft fixation, all-inside meniscus repair devices, and suture-tape augmentation systems.
These are the implants that appear on an arthroscopy or ACL bill — and, like joint-replacement implants, they are charged separately from the package.
Manufacturers' own videos
Rather than describe these systems second-hand, here are the manufacturers' own official videos. Nothing loads from YouTube until you click. These are the companies' own materials, included so you can see the devices described — not as an endorsement of one brand over another.
What robotic-arm assistance does — and what it does not
"Robotic knee replacement" is the most misunderstood phrase in this field. No robot performs a knee replacement. These are surgeon-controlled tools, and the distinction matters.
What it does
- Planning. With Mako, a pre-operative CT scan builds a three-dimensional model of your knee, on which implant size and position are planned before the day of surgery.
- Intra-operative adjustment. In theatre the surgeon checks that plan against your actual ligament tension and adjusts it before any bone is cut.
- Bounded cutting. The robotic arm provides a defined boundary while the surgeon cuts, so the cuts follow the agreed plan.
What it does not do
- It does not operate by itself, and it does not make decisions. The surgeon plans, cuts, balances and closes.
- It does not remove the need for surgical judgement about ligament balance — arguably the hardest part of the operation.
- It does not replace rehabilitation. Physiotherapy after surgery does more for how the knee ends up feeling than any technology in theatre.
A Mako robotic system is available at Mahavir Hospital. Whether robotic assistance suits your case depends on your anatomy, deformity and the plan for your knee, and is discussed at consultation. Conventional instrumented technique remains entirely valid, and is how most knee replacements worldwide are still done.
Why implant choice changes what you pay
Implants are charged separately from the hospital's package charge — on every category, in every room type, without exception. The package covers theatre, the surgical and anaesthesia team, the room and routine care. The implant is billed on top of it.
No implant prices are published on this page, because they vary by system and by case. The hospital package figures on the package charges page are "starting from" figures rather than quotations, and the implant sits on top of them — your total is confirmed only after consultation. That single fact explains most of the confusion when comparing quotes. A figure that sounds low may be a package figure with the implant left out; one that sounds high may include it. Before comparing anything, ask each hospital: does this include the implant, and which implant? Prices differ by manufacturer, bearing material, fixation type, and whether the system is primary or revision — revision implants are consistently the more expensive. Where robotic assistance is used, the associated costs are discussed as part of the plan.
If you have insurance, check whether your policy has an implant sub-limit. Some policies cap the reimbursable implant amount separately from room and surgical charges. If the clinically appropriate implant exceeds that cap, the difference is payable by you — and that is far better discovered before surgery than at discharge.
If you may be eligible for PM-JAY, cover applies only if you are an eligible beneficiary and are treated at a hospital empanelled under the scheme — ask about empanelment rather than assuming it. Within the scheme the package rate is set by PM-JAY, and the implant options available may be limited to scheme-approved ones. Bring your Ayushman card to the consultation so eligibility can be checked.
Who chooses the implant, and on what basis
The surgeon selects the implant. Not the patient from a price list, and not a sales representative. The inputs are clinical:
- Your anatomy — bone dimensions, the shape of the femoral condyles, any deformity present, and how far it can be corrected.
- Your bone quality — which largely determines whether cemented or cementless fixation is appropriate.
- Your ligaments — in particular whether the posterior cruciate ligament is intact and competent, which drives the CR versus PS decision.
- Your age and activity demands — what the knee will be asked to do, over how many years.
- Prior surgery — earlier operations, existing hardware, or a previous replacement being revised.
You are entitled to know which implant is planned, why, and what it costs. Ask for it to be named and quoted as its own line on your estimate — a surgeon who chose it on clinical grounds will have no difficulty explaining the reasoning.
Frequently asked questions — knee implants
Which knee implant is the best one?
There is no single best implant, and any page that names one is selling something. Stryker, Zimmer Biomet, DePuy Synthes, Smith+Nephew and others all produce well-established, regulator-approved systems used in large numbers worldwide. What varies is design philosophy, sizing range, bearing material and fixation options. The right implant is the one that fits your anatomy, matches your bone quality and ligament state, and suits your age and activity demands — a decision made by the surgeon at planning, after examining you and reviewing your imaging.
What is the difference between cruciate-retaining and posterior-stabilised implants?
A cruciate-retaining (CR) design keeps your own posterior cruciate ligament and relies on it to control how the knee rolls back as it bends. A posterior-stabilised (PS) design removes that ligament and substitutes for it mechanically, using a post on the insert engaging a cam on the femoral component. The choice depends on whether your posterior cruciate ligament is intact and competent, the degree of deformity, and the ligament balance achieved during surgery — which is why it is often finalised on the operating table.
Is a cemented or cementless knee implant better?
Neither is universally better — they are two ways of anchoring the same kind of implant. Cemented fixation uses bone cement (PMMA) to grout the component to prepared bone, giving immediate stability, and remains the most widely used approach in knee replacement. Cementless fixation uses a porous surface into which your own bone grows over subsequent weeks, and depends on good bone stock. Cemented is generally preferred where bone is osteoporotic. The choice follows your bone quality and age.
Does robotic-arm assisted surgery mean a robot performs my knee replacement?
No. Systems such as Mako are surgeon-controlled tools, not autonomous machines. A CT scan is used to build a three-dimensional plan before surgery; in theatre the surgeon checks and adjusts that plan against your actual ligament tension, then makes the cuts with the robotic arm providing a defined boundary that helps them follow the plan. The surgeon plans, performs and remains responsible for every decision. A Mako system is available at Mahavir Hospital; whether it is used in your case is a surgical judgement discussed at consultation.
Why does the implant change the cost of my knee replacement?
Because implants are charged separately from the hospital package charge, on every category and in every room type. The package covers theatre, team, room and routine care; the implant is billed on top. Prices differ by manufacturer, bearing material, fixation type, and whether the system is primary or revision. This is why two hospitals can quote very different totals for the same named operation — and why the first question about any quote is whether the implant is inside the figure. See the package charges page for the underlying schedule.
Ghutan na implant ma su farak hoy che? (Gujarati)
Mukhya farak: material (cobalt-chrome, titanium, oxidised zirconium, ane polyethylene insert no prakar), fixation (cement sathe ke cement vagar), design (cruciate-retaining ke posterior-stabilised), ane size range. Aa badha karano thi kharch pan badlay che — ane implant no kharch hospital na package ma samavesh nathi, alag thi lagse. Tamara mate kayo implant yogya che te tamari hadka ni sthiti, ligament, umar ane rojindi pravrutti par avelu che, ane surgeon consultation ma nakki kare che.
Related pages
Knee & hip replacement package charges
Starting figures by room category — primary, revision and bilateral, with the assistant-surgeon line and the PM-JAY position.
Package charges CostWhat determines knee replacement cost
The six factors that move the figure, and how insurance sub-limits and room-rent caps interact with them.
Cost determinants ProcedureKnee replacement in Surat — full guide
When replacement is needed, total versus partial, the operation itself, and the recovery timeline that follows it.
Knee replacement guide CostArthroscopy & ACL surgery charges
The keyhole-surgery schedule tier by tier — and where the sports fixation devices sit on the bill.
Arthroscopy charges