Gel injections, often containing hyaluronic acid, are a common treatment option for individuals experiencing knee pain due to osteoarthritis. This treatment aims to supplement the natural fluid in the joint, acting as a lubricant and shock absorber to reduce discomfort and improve mobility. While many find relief, it can be concerning if pain develops or worsens after the injection. Understanding the reasons for post-injection knee pain helps patients know what to expect and when to seek medical advice.
Normal Post-Injection Reactions
It is common to experience some mild, temporary discomfort in the knee following a gel injection. This reaction is typically due to the needle entering the joint and the body’s immediate response to the injected substance. Symptoms often include soreness, localized pain, mild swelling, warmth, or minor bruising at the injection site.
These mild reactions usually resolve within 24 to 48 hours. The viscous hyaluronic acid can temporarily increase joint pressure, contributing to initial stiffness and soreness. Applying ice and resting the knee often helps manage these symptoms.
Reasons for Persistent or Worsening Pain
While mild discomfort is normal, more significant, persistent, or worsening pain can indicate other reactions or complications. One such possibility is an exaggerated inflammatory response, sometimes called an “injection flare” or “pseudoseptic arthritis.” This reaction involves pronounced pain, swelling, increased warmth, and sometimes fluid accumulation in the joint, mimicking an infection. It occurs in about 1% of individuals and can develop hours to 72 hours after the injection, or even up to six days later. This condition is typically sterile, meaning no bacterial infection is present, and it often resolves with appropriate medical intervention.
A more serious, though rare, concern is a joint infection, known as septic arthritis. This occurs when bacteria enter the joint, leading to severe and rapidly increasing pain, significant warmth, redness, and swelling. Fever and chills may also be present, and it can become difficult to bear weight on the affected leg. Septic arthritis is a medical emergency requiring immediate treatment to prevent permanent joint damage.
Allergic reactions to the components of the injection are uncommon but possible. Symptoms can range from skin manifestations like rash and itching to more severe systemic reactions, such as difficulty breathing. Additionally, the needle itself can cause localized irritation or minor tissue trauma, leading to more prolonged soreness that extends beyond the typical initial discomfort. In some instances, the injection can trigger crystal-induced synovitis, such as gout or calcium pyrophosphate dihydrate (CPPD) arthritis, even if the patient has no prior history of these conditions. This involves the formation of crystals within the joint, leading to acute, painful inflammation.
Alleviating Discomfort After Injection
Limiting strenuous activities for 24 to 48 hours after the injection allows the gel to settle and reduces irritation. Gentle, non-weight-bearing movement is permissible unless otherwise advised by a doctor.
Applying ice packs to the affected knee for 15 to 20 minutes every few hours can reduce swelling and pain. Over-the-counter pain relievers, such as acetaminophen or NSAIDs like ibuprofen, can also help. Consult your doctor or pharmacist before taking new medication. Elevating the leg when resting can further reduce swelling.
When to Contact Your Doctor
Contact a healthcare provider if pain is severe or rapidly worsening, or if significant swelling, redness, or warmth at the injection site does not subside or increases. These signs could indicate a more serious issue, such as an infection or an exaggerated inflammatory response.
Fever or chills accompanying knee pain require immediate evaluation. Also seek medical consultation for an inability to bear weight, or pain that lasts much longer than a few days or intensifies over time. Any signs of an allergic reaction, such as a spreading rash or difficulty breathing, also require immediate medical attention.