A hip replacement removes the damaged ball and socket of your hip joint and replaces them with artificial components, typically made of metal, ceramic, and plastic. The surgery restores the smooth gliding motion that arthritis or injury has destroyed, and around 58% of hip replacements are still functioning 25 years later.
The Joint Being Replaced
Your hip is a ball-and-socket joint. The ball is the rounded top of your thighbone (femur), and the socket is a cup-shaped hollow in your pelvis called the acetabulum. In a healthy hip, both surfaces are covered in cartilage that creates nearly frictionless movement. When that cartilage wears away from osteoarthritis, rheumatoid arthritis, or a fracture, bone grinds against bone, causing pain and stiffness. A hip replacement recreates this ball-and-socket arrangement with four artificial parts.
The Four Parts of an Artificial Hip
The prosthesis mirrors the anatomy it replaces. First, a metal stem is inserted into the hollow center of the femur, anchoring the new joint to your thighbone. On top of that stem sits a ball, made of metal or ceramic, which takes over the role of your natural femoral head.
On the pelvis side, the worn socket is resurfaced with a metal cup. Inside that cup, a liner made of plastic, ceramic, or metal creates the gliding surface where the new ball rotates. This liner is the key to smooth movement. Today, the most common pairings are metal-on-polyethylene (a specialized plastic) and ceramic-on-polyethylene, both chosen because they produce low friction against a polished surface.
Even so, these artificial surfaces generate hundreds of times more friction than natural cartilage. Over years, this friction releases microscopic wear particles, each about 200 times smaller than a grain of sand, into the surrounding tissue. The body tries to clean up these particles with an inflammatory response that can gradually erode the bone around the implant, a process called osteolysis. When that bone loss becomes severe, the implant loosens and may need to be replaced. Modern materials with enhanced cross-linking have significantly reduced wear rates, though the trade-off is slightly more brittle plastic.
How the Implant Stays in Place
Surgeons secure the components to bone in one of two ways. Cemented fixation uses a fast-setting bone cement to bond the stem and cup directly to the surrounding bone. This provides immediate stability and is often preferred for older patients or those with weaker bone quality. Uncemented fixation relies on a textured or porous-coated surface that encourages your bone to grow into the implant over several weeks, creating a biological bond. The choice depends on your age, bone density, overall health, and the surgeon’s expertise. Many surgeons use a hybrid approach, cementing the stem while leaving the cup uncemented.
How the Surgery Is Performed
The implant itself is the same regardless of surgical approach. What differs is how the surgeon reaches the joint. Three main approaches exist, each named for the direction of the incision.
In the posterior approach, the incision is made on the back of the hip. This is the most widely used technique and gives the surgeon a clear view of the joint. A newer modification called the STAR approach preserves most of the posterior muscles and tendons, allowing quicker recovery and fewer movement restrictions afterward.
The anterior approach uses an incision at the front of the groin. Instead of cutting through muscles, the surgeon separates them to reach the joint. Because more muscle is preserved, patients often experience less pain in the first days after surgery, and the traditional movement restrictions (like not bending past 90 degrees or not crossing your legs) are typically unnecessary.
A lateral approach, through the side of the hip, is performed less frequently.
Robotic-Assisted Surgery
Some surgeons now use robotic-arm systems to assist with component placement. The robot doesn’t perform the surgery on its own. Instead, it helps the surgeon position the cup and stem with greater accuracy and precision. Studies show that patient outcomes are similar to manual surgery, but the improved positioning may help protect surrounding soft tissue and reduce the risk of components being placed at suboptimal angles.
Movement Restrictions After Surgery
Traditional posterior hip replacement comes with a set of precautions to prevent the new joint from dislocating while the surrounding tissues heal. These include not bending the hip past 90 degrees, not crossing your legs, and sleeping with a pillow between your knees. These restrictions typically last six to twelve weeks.
If your surgery was done through the anterior approach, these precautions are generally not required. Because the tendons aren’t detached during the procedure, the hip is stable enough that your movement is limited only by comfort, not by dislocation risk. This is one of the main reasons some patients and surgeons prefer the anterior approach.
What Recovery Looks Like
Most healthy patients walk without assistance within a few days of surgery. Low-impact exercise like stationary biking can begin within days. Driving typically resumes two to four weeks after surgery, and higher-impact activities that involve agility, like tennis or hiking on uneven terrain, are generally cleared around six to eight weeks.
Strengthening the muscles around your hip before surgery makes a measurable difference in recovery. Surgeons recommend exercising one to two times a day in the weeks leading up to your procedure, working up to 10 to 20 repetitions of each exercise. Simple movements you can do lying in bed, like tightening your thigh muscles and holding for five seconds, sliding your heel toward your buttocks, and performing straight leg raises, help build the strength your hip will rely on during rehabilitation.
How Long a Hip Replacement Lasts
A large-scale analysis published in The Lancet, drawing on national joint replacement registries, found that about 58% of hip replacements are still functioning at 25 years. Individual case studies from specialized surgical centers report higher rates, around 78% at 25 years, likely reflecting the expertise of high-volume surgeons and more careful patient selection. Your personal longevity depends on factors like your activity level, body weight, the materials used, and how precisely the components were positioned during surgery.
When a hip replacement does eventually wear out, a second operation called a revision surgery can replace some or all of the components. Revision surgery is more complex than the original procedure and generally has a longer recovery, which is one reason surgeons carefully consider the timing of a first hip replacement, especially in younger patients who may outlive their implant.