What Happens To The Kneecap In a Total Knee Replacement? | A

If you’re getting a knee replacement, the kneecap part can feel like the mystery chapter. The thigh bone and shin bone get shiny new surfaces, but the patella (kneecap) sits in front, gliding in a groove. So what happens to it?

Most of the time, your surgeon either smooths the underside and leaves it alone, or resurfaces it by attaching a round plastic piece to the back of the kneecap. Both paths are common. The right pick depends on your cartilage, your kneecap’s tracking, your bone shape, and your surgeon’s plan for your implant.

This article is general education. Your own knee, X rays, and symptoms steer the plan, so use this to ask sharper questions at your visits.

What The Kneecap Does And Why It Matters

Your kneecap isn’t just a “cap.” It’s a small bone inside the quadriceps tendon, and it acts like a pulley. When your thigh muscle tightens, the kneecap changes the angle of pull so your leg can straighten with less strain.

The kneecap also forms a joint with the thigh bone called the patellofemoral joint. The underside of the kneecap and the groove on the femur are coated with cartilage. Arthritis can rough up that cartilage, leading to front of the knee pain, grinding, and trouble with stairs or getting up from a chair.

After a total knee replacement, your femur and tibia surfaces are replaced, and the groove on the new femoral part is shaped to guide the kneecap. If the kneecap surface is still rough, it can stay a sore spot. If it’s handled well, the front of the knee often feels calmer as healing and strength return.

What Happens To Your Kneecap During Total Knee Replacement Surgery

During surgery, the kneecap is moved to the side or gently flipped so the surgeon can reach the knee joint. The patellar tendon and quadriceps tendon stay attached. The kneecap itself is not removed from your body.

Once the joint is open and the worn surfaces are exposed, the kneecap gets a close inspection. The surgeon checks the cartilage, the shape of the bone, and how the kneecap tracks in the groove as the knee bends and straightens with trial parts in place.

1. Shift the kneecap aside—It’s retracted to open the joint while tissues stay attached.
2. Clear bony spurs—Extra bone around the kneecap edge may be trimmed to stop catching.
3. Smooth rough cartilage—If resurfacing isn’t planned, the underside can be cleaned and evened out.
4. Measure kneecap thickness—Bone thickness matters if a plastic button is being added.
5. Test tracking with trial parts—The team watches how the kneecap glides through motion.

If resurfacing is chosen, the underside of the kneecap is cut flat, then a polyethylene “button” is cemented on. If resurfacing is not chosen, the surgeon may still do a “patelloplasty,” which can include smoothing cartilage, trimming spurs, and shaping the edges so it glides without snagging.

Patellar Resurfacing Versus Leaving The Kneecap Alone

People often hear “my kneecap was replaced” and picture a metal part. That’s not how it works. With resurfacing, the back of the kneecap gets a plastic cap. Without resurfacing, your kneecap stays bone and cartilage, with any needed smoothing done during surgery.

Surgeons vary. Some resurface most kneecaps. Others do it only when the patellofemoral cartilage is worn or when front of the knee pain stood out before surgery. AAOS notes some surgeons resurface and others don’t. AAOS total knee replacement overview.

Option	Why A Surgeon May Choose It	Tradeoffs To Know
Resurface the kneecap	Damaged cartilage, prior front pain, or worn patellofemoral joint	Extra implant part; small risk of loosening or kneecap fracture
Leave it unresurfaced	Cartilage looks decent, good tracking, or bone is thin	Front pain can persist; some people later need a second surgery
Smooth without a button	Minor wear with spurs that might catch during bending	No new surface; relief depends on cartilage quality

If your kneecap is resurfaced, the surgeon aims to keep the overall thickness close to what you started with. Too thick can tighten the front of the knee and make bending harder. Too thin can raise fracture risk. That’s why surgeons measure, cut carefully, and pick a button size that matches your bone.

If your kneecap is left unresurfaced, you may still hear terms like “denervation” or “edge trimming.” That usually means the surgeon used a cautery tool around the rim to quiet pain fibers and removed small spurs that can rub. It’s still your kneecap, just tidied up.

None of these paths guarantees a perfect outcome. A knee replacement is still a major change to the mechanics of your leg. What matters most is a stable implant, good alignment, and a kneecap that tracks smoothly.

How Surgeons Decide On Kneecap Resurfacing

So what pushes the decision one way or the other? It’s rarely a single checkbox. The surgeon blends what they see during surgery with what you felt before surgery and what the implant design expects.

• Grade the cartilage wear—Bare bone, deep cracks, or soft cartilage may tilt toward resurfacing.
• Weigh your front of the knee pain history—Longstanding pain with stairs can point to the patellofemoral joint.
• Check kneecap thickness and bone quality—Thin bone can raise fracture risk if too much is cut.
• Watch tracking with trial components—A stable glide can make leaving it alone feel safer.
• Note inflammatory arthritis patterns—Some conditions wear the kneecap cartilage early and evenly.
• Match the implant’s groove shape—Trochlear design affects how forgiving the tracking is.

Ask whether your surgeon resurfaces most kneecaps or picks case by case. If they pick case by case, ask what they saw on your kneecap cartilage and how it tracked with the trial parts. You’ll get a clearer answer than “yes” or “no.”

If you want a plain language reference for what knee replacement surgery includes, MedlinePlus explains the basic steps and the prosthesis parts. MedlinePlus knee joint replacement.

Kneecap Tracking And Soft Tissue Balancing

“Tracking” is how the kneecap slides in the groove as you bend and straighten your knee. When tracking is off, the kneecap can pull to the outside, rub, or catch. That can feel like grinding, sharp front pain, or a sense that the knee doesn’t want to bend smoothly.

During surgery, tracking is checked with trial parts in real time. If the kneecap pulls sideways, the surgeon may adjust the soft tissues, the implant position, or both. The goal is a centered glide with the knee moving through a normal arc.

• Balance ligaments—Tight or loose ligaments can twist the knee as it moves.
• Refine component rotation—Small changes in femur or tibia rotation can shift the groove line.
• Trim lateral tight tissue—A controlled “lateral release” may be used when the outer side is pulling.
• Remove catching spurs—Spurs near the kneecap edge can snag during deep bending.

Good tracking also depends on your recovery work. Swelling can shut down the quadriceps, and a weak quad lets the kneecap drift. Getting strength back is a big part of making the front of the knee feel steady.

Recovery And Daily Moves That Keep The Front Of The Knee Calm

Right after surgery, the kneecap area can feel tender even if it wasn’t resurfaced. The incision passes through tissues near the kneecap, and the joint is swollen. Early soreness does not tell you whether the kneecap was resurfaced.

Rehab is where most people notice the kneecap settling down. The aim is steady swelling control, safe range of motion, and a gradual return of quadriceps strength.

1. Ice and raise the leg—Use short sessions through the day to keep swelling down.
2. Work on straightening—Full extension helps the kneecap sit in its groove during walking.
3. Build quadriceps activation—Start with sets, then progress to leg raises as cleared.
4. Practice step mechanics—Lead up with the stronger leg, down with the surgical leg early on.
5. Ease into kneeling—Wait for clearance, then try soft surfaces and short holds.

If the front of your knee feels cranky in rehab, shorten your step and keep toes forward. Use a rail. If a move brings sharp kneecap pain, stop and tell therapy.

Clicking and clunking can happen as swelling fades and tendons glide over the new parts. If it’s not painful and your knee feels stable, it’s often a normal “new joint” sound. Pain, locking, or giving way is a different story.

Signs That Need A Call To Your Surgeon

Most kneecap sensations after knee replacement are part of healing. Still, some symptoms need a prompt check, since they can signal a kneecap issue or another problem in the new joint.

• Sudden loss of straightening—Inability to lift a straight leg can point to tendon trouble.
• A loud pop with sharp pain—This can go with a kneecap fracture or tendon injury.
• New, fast swelling and heat—Rapid change, redness, or drainage needs urgent review.
• Repeated giving way—Instability can tie to tracking, ligament balance, or component issues.
• Calf swelling or short breath—These can be signs of a clot and need urgent care.

Call your surgeon’s office if you’re unsure. They know your operation details, like whether the kneecap was resurfaced, and they can guide the next step.

Key Takeaways: What Happens To The Kneecap In a Total Knee Replacement?

➤ Most kneecaps are resurfaced or left alone based on cartilage.

➤ The kneecap stays attached; it’s moved aside during surgery.

➤ A plastic button may be cemented to the kneecap underside.

➤ Smooth tracking matters as much as the resurfacing choice.

➤ Painful locking, heat, or sudden weakness needs a call.

Frequently Asked Questions

Can I find out if my kneecap was resurfaced after surgery?

Yes. Your operative note usually lists “patella resurfaced” or a similar line. If you don’t have the note, ask the office for the implant sticker sheet or the brief op summary, which often names the patellar button size if one was used.

Does a resurfaced kneecap mean I’ll never have front of the knee pain?

No. Resurfacing can help when the underside cartilage was a pain driver, but front pain can also come from swelling, tendon irritation, weak quadriceps, or tracking issues. If pain lingers past early rehab, a therapist can check gait, strength, and range patterns.

Is it safe to kneel after a total knee replacement?

Many people can kneel later on, but it often feels strange. Start only after your surgeon clears it. Use a thick pad, keep the knee under your hip, and try short holds. Numb skin near the incision can make pressure feel odd even when the joint is fine.

What does “secondary patellar resurfacing” mean?

It’s a later surgery that adds a patellar button when the kneecap was not resurfaced during the first operation. It’s usually done for stubborn front of the knee pain after other causes are ruled out, like infection, loosening, or poor component position.

Why do I feel clicking near the kneecap when I stand up?

As swelling drops, tendons and soft tissues start sliding more freely over the new groove and edges. Mild clicking that isn’t painful is common. If clicking comes with a “catch” that blocks motion, or sharp pain each time, it’s worth a check with your surgeon.

Wrapping It Up – What Happens To The Kneecap In a Total Knee Replacement?

If you landed here asking what happens to the kneecap in a total knee replacement?, the core answer is simple. It’s assessed, cleaned up, and either resurfaced with a plastic button or left unresurfaced. Both are normal choices.

Your best move is to ask what was done in your own case, then put your energy into swelling control and quadriceps strength. A smooth track and a strong quad make the front of the knee feel steady as you get back to daily life.