A knee replacement looks like a set of smooth, metallic caps that fit over the reshaped ends of your bones, with a plastic cushion sandwiched between them. From the outside, a replaced knee looks much like a natural one, though it will carry a vertical scar down the front and go through weeks of swelling and bruising before settling into its final appearance. Here’s what to expect at every stage.
What the Implant Looks Like
A total knee replacement has four main parts. The femoral component is a curved, polished piece of cobalt-chromium that caps the bottom end of your thighbone, mimicking the rounded shape your natural bone once had. It’s the part that glides when you bend and straighten your leg.
Sitting on top of your shinbone is the tibial component, a flat metal tray made from titanium or cobalt-chromium. It sometimes has a short stem that anchors down into the center of the bone for extra stability. Snapped into this tray is a polyethylene liner, a dense medical-grade plastic that acts as a cushion between the two metal surfaces. This liner does the job your cartilage used to do, absorbing shock and allowing smooth movement. It’s considered the “weak link” of the system because it can gradually wear down over years of use, but modern versions last 15 to 20 years or more for most people.
On an X-ray, the implant is immediately visible: bright white metallic outlines on the end of the femur and the top of the tibia, with a dark gap between them where the plastic spacer sits (plastic doesn’t show up on X-rays). If you touch your knee after healing, you may feel the edges of the metal components just beneath the skin, especially along the inner side where there’s less soft tissue covering them.
Partial vs. Total Replacement
Not every knee replacement covers the entire joint. In a partial (unicompartmental) replacement, only the damaged compartment of the knee gets resurfaced, leaving the healthy bone, cartilage, and ligaments on the other side untouched. The implant is significantly smaller, covering roughly a third of the joint surface instead of the whole thing. On an X-ray, you’ll see metal on one side of the knee and natural bone on the other, which looks noticeably different from the full metallic outline of a total replacement.
The Surgical Incision
The standard approach uses a vertical incision running straight down the front of the knee. Most incisions fall somewhere between 6 and 10 inches long, depending on your body size and the complexity of the procedure. Surgeons typically close the skin with staples or non-absorbable sutures, which are removed at a follow-up visit about two weeks later. Minimally invasive techniques use shorter incisions, sometimes as small as 4 inches, though the implant inside looks the same regardless of incision length.
Once fully healed, the scar fades to a thin, pale line for most people. It remains slightly raised and firm to the touch for several months before softening. The scar is most visible when you straighten your leg completely, and it tends to blend in more as time passes.
What Your Knee Looks Like Right After Surgery
In the first few days, your knee will be wrapped in a bulky dressing and may have a drain to collect excess fluid. Once the bandages come off, expect significant swelling that makes the knee look puffy and tight, sometimes extending into your calf and thigh. Bruising appears as deep purple or blue discoloration that can spread well beyond the incision site, sometimes traveling down the shin or up toward the hip simply due to gravity pulling blood under the skin. This bruising typically fades within one to two weeks, shifting through shades of green and yellow before disappearing.
Moderate to severe swelling is normal for the first few days to weeks. It then tapers to mild or moderate swelling that can linger for three to six months. Many people are surprised by how long this stage lasts. Icing, elevation, and compression help, but some puffiness around the knee is simply part of the healing timeline. Your knee won’t reach its final shape and size for several months.
What a Healed Knee Replacement Looks Like
After full recovery, a replaced knee looks remarkably normal. The scar is the most obvious visual difference. Some people notice their knee sits slightly differently than before, particularly if they had a significant bow-legged or knock-kneed alignment that the surgery corrected. The overall contour of the knee may feel firmer or more angular than a natural joint because the metal components sit just beneath the surface, but to a casual observer, there’s little to distinguish it from the other knee.
Range of motion also affects appearance. Most people regain enough bend to walk, climb stairs, and sit comfortably, but a fully replaced knee rarely bends quite as deeply as a healthy natural knee. This means the knee may look slightly less flexed during activities like squatting compared to the other side.
Signs That Something Looks Wrong
In the first four to six weeks after surgery, certain visual changes around the incision can signal infection or other complications. Cloudy or discolored drainage from the wound, excessive redness that spreads outward from the incision (rather than gradually fading), wound edges that pull apart instead of closing, and drainage that continues longer than expected are all warning signs. Years after surgery, new swelling or redness in a previously healed knee can indicate a late infection, which requires prompt evaluation. A healthy healing knee should show steady improvement week over week: less swelling, less bruising, tighter wound edges. Any reversal of that pattern is worth having checked.