Knee replacements are among the most commonly performed and highly successful orthopedic surgical procedures. A knee replacement is done when the knee joint has worn out, most often as a result of wear-and-tear arthritis.
When a knee replacement is performed and the rehabilitation has been completed, more than 90% of patients will rate their outcome as good or excellent. However, not everyone has a pain-free knee after the procedure.
About 10% of patients will not consider their surgery a complete success. Some complications of knee replacement are obvious. Patients who have an infection in their replacement or fracture the bone around their replacement are expected to have less successful results. However, the most common reason people complain of poor results is not a major infection or fracture, but rather persistent pain around their newly replaced joint.
Causes of Pain After Knee ReplacementThe most important step in finding a solution to persistent discomfort is to first determine the cause of the pain. Without this knowledge, it is very difficult to find an appropriate treatment. The most common causes of pain after knee replacement include:
- Loosening or Wearing of the Implant
This is most often the cause of pain years or decades after the knee replacement; however, it is seldom the cause of persistent pain right after surgery.
Infection is a serious and worrisome concern. Any increase in pain after knee replacement should raise concerns for infection. Most often, the signs of infection are obvious, but subtle infections may be the cause of persistent discomfort.
- Patellofemoral (Kneecap) Problems
Kneecap problems are a common cause of knee replacement pain. Significant forces are applied to the kneecap, even with normal activities, such as getting up from a chair or walking down stairs. Getting a kneecap to perform well with a replacement can be technically challenging even for a skilled surgeon.
- Alignment Problems
Many patients focus on the knee replacement implant brand or type. But most surgeons will tell you the brand matters much less than how well the implant is put in. A poorly aligned implant may not function well, no matter the brand. Surgeons are investigating if computer navigation will help improve implant alignment.
Evaluating Pain After Knee ReplacementYour surgeon will take several steps to evaluate your pain. The first step is talking to you. Pain can have many different qualities, and the type of pain can help you and your doctor understand the underlying cause. For example, pain when first getting up (start-up pain) is common after a knee replacement but usually resolves after a few months. Persistent start-up pain can be a sign of loosening of an implant. Pain when going up and down stairs is suggestive of a kneecap problem.
Your surgeon will then examine the knee. A physical exam can help identify infection, stiffness and alignment issues. Ensuring that the mechanics of the knee replacement are sound is important. Just like having the proper alignment in your car, it is important that the knee replacement be properly aligned and balanced.
X-rays and other studies can assess alignment and loosening. Subtle loosening may not show up on a regular X-ray, and a bone scan or MRI may be performed. Laboratory studies can show signs of a subtle infection.
Treatment of a Painful Knee ReplacementAs stated before, the most important step is understanding the cause of pain, since blindly trying to treat pain without knowing the cause is unlikely to lead to a good result. In some situations, pain may be treated with medications and physical therapy. In other cases, particularly if loosening, infection or alignment issues are suspected, another surgery called a revision knee replacement may be necessary. The revision surgery may be minimally invasive or it may require removing the implanted knee and starting over.
Gonzalez MH and Mekhail AO. "The Failed Total Knee Arthroplasty: Evaluation and Etiology" J Am Acad Orthop Surg November/December 2004; 12:436-446.