Knee replacement surgery is a common and effective procedure for severe knee arthritis. While it often brings significant pain relief and improved mobility, some patients still experience discomfort or pain afterward. This persistent pain may lead them to explore injections to manage symptoms. Understanding the reasons for this post-surgical pain and the role injections can play is important.
Reasons for Post-Surgery Pain
Even after knee replacement, patients may experience continued pain for reasons not directly related to the implant. Soft tissue inflammation around the new joint is a common source of discomfort, potentially involving conditions like tendinitis or bursitis. Pain can also originate from the kneecap area, known as patellofemoral pain, or from scar tissue that forms during the healing process.
Nerve-related pain, referred to as neuropathic pain, can occur due to irritation or damage to nerves around the knee during surgery. Sometimes, pain felt in the knee may be referred from other areas, such as the hip or spine. Less commonly, ongoing arthritis in other parts of the knee (if a partial replacement was performed) or in other joints can contribute to persistent pain.
Common Injections and Their Purpose
Several types of injections may be considered for pain relief after knee replacement, targeting issues not caused by implant failure. Corticosteroid injections, often called cortisone shots, are used for their anti-inflammatory properties. These are administered around the joint, into areas like inflamed bursae or tendons, to reduce localized swelling and pain. Direct injection into the prosthetic joint is avoided due to infection risks.
Hyaluronic acid injections, also known as viscosupplementation, aim to restore lubrication and shock absorption in a natural joint. Their role after total knee replacement is limited or not recommended directly into the prosthetic joint, as artificial joint surfaces are designed to move smoothly on their own.
Platelet-rich plasma (PRP) and stem cell injections are regenerative therapies that use components from a patient’s own body to promote healing. PRP involves concentrating platelets from blood, which contain growth factors that aid tissue repair and reduce inflammation. Stem cell therapy involves injecting stem cells, often from bone marrow or fat, to help repair damaged tissues and decrease inflammation. Research on their direct application into a knee replacement joint is ongoing, with their role currently focused on surrounding soft tissue issues.
Nerve blocks and radiofrequency ablation are options for managing neuropathic or persistent localized pain by targeting specific nerves outside the joint. A nerve block involves injecting an anesthetic near nerves to temporarily interrupt pain signals. Radiofrequency ablation uses heat generated by radio waves to deactivate specific pain-transmitting nerves, offering longer-lasting relief.
Safety and Effectiveness After Joint Replacement
Injections after knee replacement require careful evaluation of safety and effectiveness. A primary concern with injecting directly into a prosthetic joint is the risk of periprosthetic joint infection (PJI). An artificial implant creates a surface where bacteria can form biofilms, making infections difficult to treat. For this reason, injections are directed at soft tissues surrounding the knee, not into the joint space.
Direct injections into the prosthetic joint could also impact implant materials or stability. While injections provide temporary relief for soft tissue inflammation or nerve pain, their effectiveness depends on correctly identifying the pain’s cause. They are not a solution for implant issues like loosening or wear, which require surgical revision. Studies also suggest a correlation between postoperative intra-articular corticosteroid injections and an increased risk of PJI.
Consulting Your Healthcare Provider
For persistent pain after knee replacement, consult a healthcare provider. An orthopedic surgeon or pain management specialist can conduct a thorough evaluation to determine the pain’s specific cause. This assessment may involve a physical examination, imaging (like X-rays), and blood tests to rule out complications such as infection or implant issues.
Do not self-diagnose or seek injections without a comprehensive medical assessment. Injections are one tool within a broader pain management strategy. A personalized approach may also include physical therapy, oral medications, or, rarely, revision surgery if other treatments are ineffective and an underlying problem is identified.