Revision hip and knee replacement: when is it needed?

Introduction

Hip and knee replacements are among the most reliably successful operations in all of medicine. The vast majority of patients who undergo joint replacement experience a substantial and lasting improvement in pain and function. Most implants remain well-fixed and well-functioning for 15 to 20 years or more.

But joint replacements are not permanent devices, and for some patients — whether due to wear, loosening, infection, or another complication — the original implant eventually needs to be revised. Understanding why revision surgery is needed, and what it involves, helps patients facing this situation to approach it with realistic expectations.

What causes a joint replacement to fail?

The term “failure” covers a range of problems that can develop at different points after the original operation. The most common causes differ slightly between hip and knee, but the broad categories are similar.

Loosening

Over time, the bond between the implant and the bone can weaken. This is called aseptic loosening — loosening without infection. It may result from gradual wear of the plastic bearing surface, generating tiny particles that trigger the body’s immune system to resorb the surrounding bone. It can also reflect a problem with how the implant integrated with the bone in the first place. Loosening typically causes a deep, aching pain that is worse with activity and may be present at rest in advanced cases.

Wear

The bearing surfaces in a joint replacement — the plastic liner in a hip socket, or the polyethylene insert in a knee — gradually wear with use. In modern implants with highly cross-linked polyethylene, this process is slow and predictable. But in older implants, or in very active or heavy patients, wear can occur sooner. The debris generated can cause bone loss around the implant, and the worn surfaces may no longer provide the correct alignment or stability.

Infection

Periprosthetic joint infection is one of the most serious complications of joint replacement. Bacteria can reach the implant at the time of the original surgery, or spread to it from elsewhere in the body years later. Infection around a joint replacement is difficult to treat with antibiotics alone — the bacteria adhere to the metal surfaces and form a protective biofilm. In most cases, revision surgery is required to remove the implant, treat the infection, and implant new components.

Instability

In hip replacement, instability manifests as dislocation — the ball coming out of the socket. In knee replacement, instability refers to a knee that buckles or gives way. Both can result from implant position that is outside the optimal range, soft tissue imbalance, or wear and deformation of the bearing surfaces. Recurrent instability that cannot be managed conservatively is a common indication for revision.

Fracture around the implant

A periprosthetic fracture — a fracture in the bone immediately around an existing implant — is increasingly common as the population of patients with joint replacements ages. These fractures are often the result of a fall onto a leg that already has weakened bone around the implant stem. Surgical management typically requires revision of the implant component in addition to fracture fixation.

What are the signs that revision may be needed?

Pain is the most common symptom that brings patients back for evaluation. Pain that returns after a period of good function, or pain that has never fully resolved after the original operation, warrants investigation. The character of the pain can be informative: start-up pain that eases with movement suggests loosening; constant pain may suggest infection; mechanical clunking or giving way suggests instability.

Other symptoms include swelling of the joint that is new or worsening, a change in the feel or alignment of the limb, or generalised fatigue and malaise — particularly with low-grade infection.

The investigation of a painful joint replacement includes plain X-rays comparing the current appearance to previous images, blood tests to look for markers of infection and inflammation, and sometimes further imaging such as bone scan or CT. Aspiration of the joint — sampling the fluid — is often the most reliable test for infection.

What does revision surgery involve?

Revision joint replacement is substantially more complex than the original operation. The surgeon must remove well-fixed components from bone — a process that can require specialised tools and is more time-consuming than the primary procedure. Bone loss from wear, loosening, or infection often needs to be addressed using bone graft, metal augments, or specialised revision implants that extend further down the femur or across a greater area of the pelvis.

The goal is to restore stable, well-aligned, and well-fixed components that will provide lasting function. In cases of infection, a two-stage approach is sometimes used: the original implant is removed, a temporary antibiotic-loaded spacer is placed to treat the infection over several weeks, and then new implants are inserted at a second operation once the infection has cleared.

Recovery after revision surgery

Recovery from revision joint replacement takes longer than recovery from a primary replacement. Patients can generally expect to be on the ward for several days and to require walking aids for a longer period. Full recovery — returning to normal daily activities without significant restriction — typically takes three to six months, depending on the complexity of the procedure and the degree of bone loss encountered.

Weight-bearing restrictions after revision hip or knee replacement vary depending on what was done at surgery. Your surgeon will provide specific guidance based on the implants used and the quality of bone at the time of the operation.

When to seek advice

If you have a hip or knee replacement that is causing new or worsening pain, or if you have concerns about how your joint is functioning, it is worth seeing an orthopaedic surgeon for evaluation. Not every painful replacement requires revision — sometimes the investigation identifies a treatable cause that does not require a return to the operating room. But early assessment is important: problems such as infection or progressive bone loss are better managed before they become more extensive.

Dr Mooney consults at Orthopaedics 360, 204 Greenhill Road, Eastwood. Referrals from your GP are required for a Medicare rebate. You can also contact the rooms directly on (08) 7077 0157.