A knee replacement is a common surgery that can relieve pain and restore function in a knee joint damaged by arthritis. During knee replacement surgery, the damaged parts of the knee joint are removed and replaced with artificial components made of metal and plastic. The artificial knee joint is secured to the bone with bone cement. Over time, it’s possible for the bond between the artificial knee and the bone to loosen. A loose knee replacement is also known as aseptic loosening. When this happens, you may feel pain, hear clicking or other unusual noises from the knee joint, and notice a change in your ability to walk and move the joint. Identifying symptoms right away and seeing your doctor can help avoid complications from a loose knee replacement.
What causes a knee replacement to become loose?
There are several potential causes for a loose knee replacement:
- Normal wear and tear over many years of use can degrade the bone cement used to hold the implant in place.
- If there is inadequate supporting bone, the implant components can loosen from the bone.
- An injury, fall, or other trauma may disrupt the bone-implant interface.
- If an infection occurred after surgery, it can weaken the bond.
- Being overweight or overly active can place excessive stress on the bond between the bone and implant.
- A loose implant may also result from a minor surgical error during the replacement procedure.
Over time, the constant minor motion of a loose knee replacement can cause inflammation and deterioration of the bone. That’s why it’s important to have any symptoms evaluated promptly.
Main symptoms
Here are the main signs and symptoms that your knee replacement may be loose:
Pain
One of the first and most common symptoms is pain in the knee joint that is unlike the pain you had prior to surgery. This new knee pain may occur while walking, standing, climbing stairs, or moving the joint. The pain may be mild at first but gradually increases over time. Resting the knee may help temporarily, but the pain returns when you start moving again.
Instability
You may develop a feeling that your knee joint is unstable or loose when you walk or bear weight on that leg. This differs from the stiffness or inflexibility you may have felt in the joint prior to a knee replacement. Along with this sense of instability, you may hear and feel clicking, clunking, or other strange noises when moving the knee.
Swelling
Inflammation can occur around a loose knee implant, leading to swelling in and around the joint. You may notice puffiness or fullness when examining your knee replacement site. There may be visible bruising if the swelling is significant.
Difficulty walking
Increased pain, instability, stiffness, and swelling can make it more difficult to walk normally. You may develop a limp or change your gait to accommodate the loose implant. Walking and standing for long periods may become challenging. Going up and down stairs may also increase your discomfort and difficulty moving the joint.
Loss of function
Along with increased difficulty walking, you may notice a decline in your ability to move and use your knee for daily activities. Bending, squatting, kneeling, and using the stairs could become more difficult. A decrease in range of motion is another sign of a problem.
Visible implant loosening
In some cases, X-rays may reveal that the implant has become detached from the bone. However, it’s important to note that a loose knee replacement won’t always be obvious on an X-ray. You may have a loose implant causing symptoms before it shows up in imaging.
Risk factors
Certain factors can increase your risk of developing a loose knee replacement:
- Being overweight – Excess weight puts added stress on the implant that can cause loosening over time.
- High activity levels – Very active lifestyles and high-impact activities may accelerate loosening in some cases.
- Unstable or misaligned implant – This can cause uneven wear and loosing of the components from bone.
- Poor bone quality – Inadequate bone density can lead to poor cementing or fixation of the implant.
- Younger age – Younger, more active patients generally have a higher risk of implant loosening requiring revision surgery.
- Chronic conditions – Medical problems like rheumatoid arthritis, osteoporosis, or bone cancer increase risk.
If you have any of these risk factors, be especially alert for any signs of implant loosening and promptly report symptoms to your orthopedic surgeon.
Diagnosis
If you notice any of the symptoms of a loose knee replacement, make an appointment to see your orthopedic surgeon right away. Early diagnosis and treatment are key to avoiding complications. The doctor will examine your knee joint and review your symptoms. They may order one or more of the following tests:
- X-ray – This can sometimes detect a loose implant, bone loss, or other signs of loosening. Serial x-rays over time may be needed.
- CT scan – Provides a more detailed view compared to x-rays and may spot subtle loosening.
- MRI – This scan can identify inflammation and damage to soft tissues surrounding a loose implant.
- Bone scan – Increased blood flow to bone tissue affected by a loose implant may be detected.
- Blood tests – These can help rule out infection as a cause of a loose knee replacement.
Your doctor will thoroughly assess the results of your evaluation to determine if revision surgery is required to fix or replace the loose implant.
Treatment
If your knee replacement is found to be loose, the main treatment option is corrective, or revision, surgery. Your orthopedic surgeon will take steps to refit the implant into your bone or replace part or all of the artificial components. Here’s an overview of the revision procedure:
- The old, loose implant is removed from your knee joint.
- Damaged bone and tissue are cleaned up and repaired.
- A new implant is properly fitted and secured into healthy bone.
- Spacers, cement, bone grafts, or other methods are used to stabilize the new implant.
- Your joint mobility and alignment are improved.
Recovering from knee revision surgery takes time. You’ll need to restrict activity to allow the joint and bone to heal. Physical therapy helps restore strength and function. With a successful procedure, your knee pain and other symptoms are typically relieved.
Prevention
While you can’t always prevent a knee replacement from loosening over time, these proactive measures can help reduce your risk:
- Maintain a healthy weight to avoid placing excess stress on your joint replacement.
- Talk to your surgeon about appropriate levels of activity to prevent excessive wear.
- Do strengthening and range-of-motion exercises to support your knee joint.
- Use proper posture and body mechanics during activities.
- Avoid high-impact activities and trauma to the knee joint.
- Report any symptoms, like pain or instability, to your doctor right away.
Closely following your surgeon’s recommendations after surgery is also important to ensure proper healing and implant integration.
Outlook
A loose knee replacement is relatively uncommon, but this complication can happen years after a total knee replacement. The good news is that with prompt diagnosis and revision surgery, the majority of patients go on to have good pain relief and knee function once again. Close follow-up care and physical therapy after revision surgery are key factors in ensuring the best outcome.
Conclusion
A loose artificial knee is a serious concern. Paying attention to symptoms like increased knee pain, instability, and loss of function allows early detection. Have your doctor promptly evaluate any changes to determine if your implant has become loose. Following your surgeon’s advice after a knee replacement, maintaining a healthy weight, and avoiding overuse of your knee joint may help prevent loosening. Revision surgery can successfully replace a loose knee replacement. With proper follow-up care and physical therapy, most patients experience significantly reduced knee pain and restored mobility.