Hip replacement surgery involves removing the damaged ball-and-socket of your hip joint and replacing them with artificial components made of metal, ceramic, and plastic. The procedure typically takes one to two hours, and most people are standing or walking with assistance the same day. From the outside, you’ll see a single incision on the hip that heals into a scar. From the inside, the surgery is a precise mechanical swap: your worn-out joint surfaces come out, and engineered replacements go in.
What the Implant Looks Like
A hip replacement implant has four main parts that mirror the anatomy of your natural hip. Two are fixed into bone, and two move against each other to recreate the ball-and-socket motion.
- Femoral stem: A tapered metal post, usually made from a titanium alloy, that fits down into the hollow center of your thighbone. It anchors the entire lower half of the new joint.
- Femoral head: A smooth ball that attaches to the top of the stem. It’s typically made from a cobalt-chromium alloy or ceramic. This replaces the natural ball at the top of your thighbone.
- Acetabular shell: A metal cup, also usually titanium, that your surgeon presses into the hip socket in your pelvis. It replaces the bony socket.
- Liner: A smooth insert that sits inside the metal cup. It’s made from highly durable plastic (polyethylene) or ceramic. The ball glides against this liner every time you move your hip.
The combination of materials matters because the ball and liner create a friction pair that needs to last decades. Ceramic-on-ceramic and ceramic-on-plastic are common pairings, each chosen based on your age, activity level, and anatomy. The assembled implant looks roughly like a chrome-and-white replica of the top of your femur seated into a shallow cup.
How the Implant Stays in Place
There are two ways to anchor the implant to your bone. In a cementless (or “press-fit”) approach, the surgeon shapes the bone precisely so the implant wedges in tightly. The surfaces of these implants have a porous coating that your bone gradually grows into over the following weeks, locking everything in place permanently. This method tends to perform better in younger, more active patients with strong bone.
In a cemented approach, the surgeon applies a fast-setting bone cement to bond the implant to the surrounding bone. This provides immediate stability and works well for older patients or those with weaker bone density. Both methods produce excellent long-term results when matched appropriately to the patient. Many surgeons use a hybrid strategy, cementing the stem but press-fitting the cup, depending on bone quality in each area.
Where the Incision Goes
The most common approach worldwide is the posterior approach. You lie on your side, and the surgeon makes an incision along the back of your hip, starting a few centimeters above the bony prominence on the outside of your hip and extending several centimeters below it. The surgeon works between and through the muscles in the buttock area to reach the joint.
The direct anterior approach has gained significant popularity in recent years. For this technique, you lie on your back, and the incision goes on the front of your hip, starting a few centimeters below and to the side of the bony point at the front of your pelvis. This approach is considered muscle-sparing because the surgeon passes between muscles rather than cutting through them, working through natural gaps between muscle groups. It’s the only common hip replacement approach that takes advantage of both an intermuscular and internervous plane, which can translate to less muscle damage and a faster early recovery for some patients.
A traditional incision runs about 25 centimeters (roughly 10 inches). Minimally invasive versions of both approaches use smaller incisions, though the internal work is essentially the same. The scar fades over time and, depending on your skin tone and healing, often becomes a thin pale line within a year.
What Happens Before You Go Under
Most hip replacements are performed under regional anesthesia, not general. At high-volume joint replacement centers, more than 90% of cases use a spinal block. An anesthesiologist injects local anesthetic into the fluid surrounding the spinal nerves in your lower back. Within minutes, you lose sensation and the ability to move the lower half of your body. You’re then given light sedation so you’re unconscious during the procedure, but you breathe on your own throughout. There’s no breathing tube involved.
This matters for recovery. Compared to general anesthesia, regional anesthesia typically means less grogginess when you wake up, less nausea, reduced blood loss during surgery, and a lower risk of blood clots afterward. General anesthesia is still available and sometimes necessary based on your spine anatomy or other medical factors, but regional is the standard for most patients.
Step by Step in the Operating Room
Once anesthesia takes effect, the surgical team positions you (on your side for a posterior approach, on your back for an anterior one) and cleans the skin around your hip. The surgeon makes the incision and works through the soft tissue layers to expose the hip joint.
The first major step is dislocating the femoral head from the socket. The surgeon then uses a specialized saw to cut through the neck of the femur, removing the damaged ball entirely. That piece of bone, often visibly worn and pitted from arthritis, comes out of the wound.
Next, the surgeon turns attention to the socket. Using progressively larger dome-shaped reamers, they reshape the hip socket to accept the new metal cup. The acetabular shell is pressed or cemented into place, and the liner is snapped into it.
Then the femur is prepared. The surgeon uses a series of rasps, shaped like the final implant, to hollow out and shape the inside of the thighbone canal. Once the fit is right, the femoral stem is either pressed into the canal or cemented in. The new ball is placed on top of the stem, and the surgeon reduces the joint, meaning the ball is seated back into the new socket. The team tests the range of motion and stability right there on the table, checking that the leg length is correct and the joint doesn’t want to pop out of place. The incision is then closed in layers.
The entire process takes one to two hours for a straightforward primary replacement.
Robotic-Assisted Surgery
A growing number of hip replacements now involve robotic assistance. The surgeon still performs the operation, but a robotic arm helps execute the bone cuts and implant positioning with enhanced precision. Before surgery, a CT scan or intraoperative imaging creates a 3D model of your hip, and the surgeon plans exact implant placement on a computer.
During the procedure, the robotic system guides the surgeon’s movements and can restrict cutting outside the planned boundaries. The result is measurably more accurate cup and stem positioning. Studies comparing robotic-assisted to conventional surgery found that patients in the robotic group were over five times more likely to have their cup placed within the ideal “safe zone,” which is the range of angles associated with the best long-term outcomes and lowest risk of dislocation. Stem alignment was also more consistent. This technology is particularly helpful for less experienced surgeons and in technically challenging cases, such as in patients with obesity, where anatomical landmarks are harder to identify.
What Recovery Looks Like Immediately After
You’ll wake up in a recovery area with the sensation gradually returning to your legs over the next hour or two. Many patients stand and take their first steps with a walker the same day as surgery, guided by a physical therapist. You can typically put your full weight on the new hip right away unless your surgeon specifies otherwise.
Hospital stays have shortened dramatically. Same-day discharge rose from 1.5% of hip replacement patients in 2016 to over 25% by 2021. If you’re generally healthy and have help at home, you may leave the hospital within hours. Others stay one night. A two or three-night stay, once standard, is now reserved for patients with more complex medical needs.
In the first days at home, you’ll walk with a walker or crutches, gradually increasing your distance. Most people transition to a cane within a few weeks and walk unassisted within four to six weeks, though the full timeline varies. The new joint will feel stiff and sore initially, but the deep, grinding pain of the arthritic hip is typically gone from the moment you wake up.