Arthroplasty is a surgical procedure that restores the function of a damaged joint. It most commonly involves replacing part or all of a joint with an artificial implant, though in some cases surgeons resurface the existing bone instead. Hips and knees are the joints most frequently treated, with millions of these procedures performed each year in the United States alone.
How Arthroplasty Works
The basic idea is straightforward: a joint that’s too damaged to function properly gets rebuilt. In a total joint replacement, the surgeon removes the worn-out surfaces of the joint and replaces them with artificial components called prostheses. In a partial replacement, only the damaged portion of the joint is swapped out, preserving healthy bone and tissue. A third option, resurfacing, caps the existing bone with a smooth metal covering rather than removing it entirely.
Modern implants are made from combinations of metals and plastics designed to mimic the smooth gliding motion of a natural joint. The metal components are typically cobalt-chromium or titanium alloys, while the bearing surface that allows the joint to move with minimal friction is a specialized high-density plastic called polyethylene. Newer versions of this plastic, known as highly cross-linked polyethylene, wear down roughly 40 to 50 percent less than older formulations, which helps implants last longer.
Joints Most Commonly Replaced
Knees and hips account for the vast majority of arthroplasty procedures. The American Joint Replacement Registry, the world’s largest database for these surgeries, has captured over 4.3 million hip and knee procedures since 2012, with volume growing 18 percent in the most recent reporting year. Shoulder replacements are the next most common, followed by ankles, elbows, and wrists, though these are performed far less frequently.
Why Arthroplasty Is Recommended
Osteoarthritis is the most common reason someone ends up needing a joint replacement. This is the “wear and tear” form of arthritis where the cartilage cushioning a joint gradually breaks down, leaving bone grinding against bone. Other conditions that can lead to arthroplasty include rheumatoid arthritis, avascular necrosis (where the bone loses its blood supply and begins to collapse), and certain fractures.
Surgery is not the first option. Doctors typically recommend it only after conservative treatments have been tried for six months or more without adequate relief. In practical terms, the threshold for surgery usually looks like this:
- Pain that doesn’t respond to anti-inflammatory medications after months of use
- Sleep disruption from joint pain on a regular basis
- Significant walking limitations, such as being unable to walk more than a few blocks
- Inability to work or carry out daily activities because of pain or stiffness
- Loss of joint function that physical therapy and injections haven’t improved
Traditional vs. Robotic-Assisted Surgery
Most arthroplasties are still performed manually, with the surgeon using specialized cutting guides and tools to shape the bone and position the implant. Over the past decade, robotic-assisted systems have become increasingly available, and roughly one in three knee replacements at some major centers now use a robotic arm to guide the bone cuts.
The clinical outcomes, however, are remarkably similar between the two approaches. A Cleveland Clinic analysis of 895 patients found no significant differences in pain scores, complication rates, or patient-reported quality of life at one year. Robotic surgery did show advantages in shorter hospital stays (about half a day versus just over one day) and higher rates of patients going directly home rather than to a rehabilitation facility. Manual surgery, on the other hand, had shorter operating times (105 minutes versus 113 minutes) and patients needed fewer physical therapy visits afterward.
The robotic arm’s main technical advantage is its precision in making bone cuts, which helps surgeons balance the ligaments around the joint more accurately. This tends to be most useful in patients with more complex deformities rather than straightforward cases.
How Long Implants Last
One of the most common concerns people have about joint replacement is whether the implant will eventually wear out and need to be replaced again. The answer is reassuring for most patients. A large-scale analysis published in The Lancet, drawing on data from 14 national registries, found that 82 percent of total knee replacements were still functioning well at 25 years. Partial knee replacements had a somewhat lower survival rate of about 70 percent at the same time point.
Several factors influence how long your implant lasts. Younger, more active patients tend to wear through implants faster simply because they put more miles on them. Body weight matters too, as heavier loads accelerate wear on the plastic bearing surfaces. Advances in implant materials, particularly the newer cross-linked plastics, are expected to push longevity even further for patients receiving implants today.
What Recovery Looks Like
Recovery from arthroplasty follows a fairly predictable timeline, though individual experiences vary based on age, overall health, and which joint was replaced. Using total knee replacement as a representative example, here’s what most people can expect.
The First Week
You’ll start moving the joint and walking short distances within a day of surgery, often with a walker or cane. Early movement is essential for preventing blood clots and kick-starting the healing process. Your physical therapist will give you a set of exercises to do daily, focused on improving circulation and gently restoring range of motion. By the end of the first week, many people can put full weight on the joint without leaning heavily on their walking aid.
Weeks 4 Through 6
Most people ditch the cane by this point. If you have a desk job, you can typically return to work within four to six weeks. Jobs that involve walking, lifting, or travel may require up to three months. Some people begin driving again in this window, though you’ll need clearance from your surgeon and should not drive while taking prescription pain medication.
Week 12 and Beyond
By three months, most people have little or no pain during everyday activities and have regained a full range of motion. This is when many patients start enjoying recreational activities like golf, dancing, and cycling. High-impact sports like running, basketball, skiing, and football remain off-limits because they can damage the implant or the surrounding tissues.
The Role of Physical Therapy
Physical therapy is not optional after arthroplasty. It’s the single biggest factor you can control in determining how well your new joint works. The American Academy of Orthopaedic Surgeons recommends 20 to 30 minutes of targeted exercises two to three times a day during early recovery, plus 30-minute walks two to three times daily. The initial exercises focus on bending and straightening the joint, building strength in the surrounding muscles, and improving circulation to prevent complications. As you progress, the exercises shift toward functional movements: climbing stairs, getting in and out of chairs, and eventually returning to the activities you enjoy.
The total course of formal physical therapy typically runs 6 to 12 weeks, with a gradual transition to independent exercise. Patients who commit to their rehab program consistently recover faster and report higher satisfaction with their results than those who don’t.