How Does Joint Replacement Work?

Posted on 6/30/25 by Sarah Boudreau

Well over a million total joint replacement surgeries are performed every year. This surgery, known as arthroplasty, replaces a joint with artificial components.  

Today, we are going to walk through joint replacement, from the basic anatomy to surgical recovery.   
 

Which Joints Can Be Replaced?   

Let’s start simple. There are three types of joint:   

  • Fibrous, where the bones are connected by fibrous (dense) connective tissue 
  • Cartilaginous, where the bones are connected by a type of connective tissue, called fibrocartilage or hyaline cartilage  
  • Synovial, where the bones are separated by a joint cavity, lined by a synovial membrane, and are connected by ligaments  

Joint replacements replace synovial joints, which are the most common joints in the body. They are fluid-filled joints within a tough, outer fibrous capsule, and out of all the joint types, they allow for the most movement.  

joint-capsule

GIF from VB Suite. 

The fibrous outer capsule protects the joint and prevents it from extreme movement, while synovial fluid helps reduce friction between bones as they move.  

Additionally, some synovial joints include:  

  • Intracapsular ligaments, bands of connective tissue inside the fibrous capsule, which limit movement 
  • Menisci (sg. meniscus), which absorb impact and improve the fit between the bones forming the joint  
  • Labrums, which often stabilize ball-and-socket joints  
  • Bursae (sg. bursa), fluid-lined sacs near the joint that reduce friction between tendons and other structures  

Of all the synovial joints in the body, hip and knee replacements are the most common. However, medical expertise has advanced over the past decades, and other joint replacements, like shoulder and ankle replacements, are growing more common. One can even receive a lumbar disc replacement, replacing a damaged disc with an artificial one.   

What Goes Wrong   

Most people receive joint replacement surgery due to arthritis, or inflammation of the joint. The most common type of arthritis is osteoarthritis, which occurs when the cartilage and other tissues of the joint wear down over time. As they wear thinner and thinner, the bones are put under more pressure.   

In response, the joint ramps up production of synovial fluid, which can cause the joint cavity to swell. The bone tissue thickens, causing the bone’s articulating surface (the surface of the bone that glides over the surface of the other bone or bones forming the joint) to become bumpy, which can lead to more pain and inflammation.   

osteoarthritis-model

GIF from VB Suite. 

People with osteoarthritis can experience joint pain, stiffness, limited flexibility, swelling, and muscle weakness, and many feel a grating sensation in the affected joint.   

Other forms of arthritis lead to needing joint replacements, including rheumatoid arthritis, which occurs when the body’s immune system attacks the joints.   

A joint replacement is sometimes necessary with osteonecrosis, which occurs when an injury limits the supply of blood to the bone, causing bone tissue to die. Injuries, such as breaking a hip, can also necessitate a total joint replacement.   

Damage to a joint does not get better with time; once the joint’s tissues are worn down, the body cannot repair them. However, because joint replacement is invasive, it’s important to try other treatments, such as medication, lifestyle changes, and assistive and adaptive devices, before pursuing surgery.   

The Surgery  

Like we mentioned before, a joint replacement surgery is called an arthroplasty. This surgery gained popularity in the 1960s as medical advancements made the surgery more successful. The procedure has improved greatly over the decades, with a lower failure rate and higher-quality materials.   

For this section, we’re going to look at total hip arthroplasty (THA). THA provides short- and long-term pain relief, and it’s considered more reliable than a knee replacement.   

There are several different approaches a surgeon can take, including:   

  • Posterior, the most common approach. This involves dissection of the gluteus maximus fibers and cutting through the fascia lata distally. This approach avoids damaging the hip abductors.   
  • Direct anterior, which is growing in popularity. This requires additional expertise and a specialized operating table.  
  • Anterolateral, which is the least popular. With the anterolateral approach, the tradeoff is that the patient may have a decreased likelihood of dislocation but an increased likelihood of developing a permanent limp.  

Using a reciprocating saw, the surgeon removes the femoral head. Tissues, like the ligamentum teres, are retracted to access the acetabulum, which is the surface of the hipbone that creates the hip socket.   

THA-part-1

GIF from VB Suite. 

The acetabulum is prepared with acetabular reamers, creating the cavity shape needed for the artificial cup part of the joint. After the acetabulum has been reamed, the artificial socket is pressed into it.   

Next comes the femur—once again, a reamer is used to prepare the bone for its prosthesis. The prosthetic’s stem is either screwed or cemented to the shaft of the femur, and a ball is placed on top of the stem. A liner is then placed between the new ball and socket to reduce friction.   

THA-part-2

GIF from VB Suite. 

Sutures are used to repair the joint capsule and close the wound.   
 

Recovery  

How long does it take to recover from a joint replacement? That depends on the individual and the type of replacement—for example, it typically takes about two months after a hip replacement to participate fully in daily activities, while a knee replacement can take three months, plus another three to nine months to fully regain strength.  

After surgery, pain is managed with medication, ice, and movement.   

Patients will undergo several weeks of physical therapy to improve range of motion, decrease swelling, and strengthen muscles, so that they can get back to living their normal lives. Exercises will depend on the individual as well as on the surgical approach.   

Complications of arthroplasty include infection and peripheral nerve injury. Like other major surgeries, arthroplasty can also result in complications like venous thromboembolism (blood clot in the veins) and hospital-acquired pneumonia. In hip replacements, dislocation is an uncommon but still extant threat, particularly in the first few months after surgery.  

Teaching Joint Replacement with Visible Body  

Visible Body’s 3D models, assignments, animations, and other features give instructors the tools they need to teach future healthcare professionals about arthroplasty and the physical therapy required afterward, and our app is used by practitioners all over the world as reference and for patient communication.  

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