Persistent Pain After Knee Replacement: Why Does It Happen?
Total Knee Replacement (TKR), also known as Total Knee Arthroplasty (TKA), is one of the most successful orthopedic surgeries for relieving severe arthritis pain. Most patients experience significant improvement in pain, mobility, and quality of life.
However, 10–20% of patients continue to experience persistent pain even after technically successful knee replacement surgery. This ongoing pain can affect walking, sleep, work, and overall quality of life.
Fortunately, persistent knee pain does not always mean the implant has failed. Many patients can benefit from careful evaluation and advanced minimally invasive pain management techniques without requiring revision surgery.
What Is Persistent Pain After Knee Replacement?
Persistent post-TKA pain refers to pain that continues for more than three months after surgery despite adequate healing.
The pain may be:
- Around the front of the knee
- Medial or lateral knee pain
- Burning or nerve-like pain
- Pain while climbing stairs
- Pain during prolonged walking
- Night pain
- Pain associated with stiffness
Some patients also describe hypersensitivity around the surgical scar.
Why Does Pain Continue After Knee Replacement?
Persistent pain can occur due to several reasons.
Mechanical Causes
- Implant loosening
- Malalignment
- Instability
- Polyethylene wear
- Patellar maltracking
Infection
Even a low-grade infection may produce persistent pain and swelling.
Soft Tissue Problems
- Tendinitis
- Bursitis
- Scar tissue
- Arthrofibrosis
Nerve Pain
Many patients develop neuropathic pain because of injury or irritation of sensory nerves around the knee.
Complex Regional Pain Syndrome (CRPS)
Although uncommon, CRPS can cause severe pain with swelling and skin changes.
Referred Pain
Pain may actually originate from:
- Hip arthritis
- Lumbar spine disease
- Peripheral neuropathy
Symptoms
Patients commonly report:
- Persistent aching pain
- Sharp pain during movement
- Difficulty climbing stairs
- Pain while getting up from a chair
- Swelling
- Knee stiffness
- Feeling of instability
- Burning or electric shock-like pain
- Reduced walking distance
Evaluation of Pain After Knee Replacement
A thorough assessment is essential before deciding treatment.
Your doctor may recommend:
- Clinical examination
- X-rays
- CT scan (if required)
- Blood tests (ESR, CRP)
- Joint aspiration if infection is suspected
- Ultrasound evaluation
- Assessment of spine and hip
Only after excluding infection and mechanical failure should interventional pain procedures be considered.
Genicular Nerves: The Source of Knee Pain
The knee receives sensation from several small sensory nerves called the genicular nerves.
The commonly targeted nerves include:
- Superior medial genicular nerve
- Superior lateral genicular nerve
- Inferior medial genicular nerve
These nerves transmit pain signals from the knee joint to the brain.
What Is Genicular Nerve Radiofrequency Ablation (RFA)?
Genicular nerve radiofrequency ablation is a minimally invasive procedure that interrupts pain transmission by applying controlled heat to the sensory nerves supplying the knee.
Importantly, these nerves are sensory nerves and do not control muscle strength or knee movement.
Diagnostic Genicular Nerve Block
Before performing radiofrequency ablation, most pain specialists perform a diagnostic genicular nerve block.
A small amount of local anesthetic is injected around the target nerves.
If the patient experiences significant temporary pain relief, they are considered good candidates for radiofrequency treatment.
The case report you shared describes this approach. The patient experienced 100% pain relief for approximately six hours after the diagnostic nerve block, confirming that the genicular nerves were the pain source.
How Is the Procedure Performed?
The procedure is usually performed as a daycare procedure.
Steps include:
- Ultrasound identification of genicular neurovascular bundles
- Fluoroscopic confirmation of bony landmarks
- Local anesthesia
- Placement of radiofrequency needles
- Sensory stimulation testing
- Radiofrequency lesioning of target nerves
In the published case, radiofrequency was applied at 80°C for 90 seconds to the superior medial, superior lateral, and inferior medial genicular nerves under combined ultrasound and fluoroscopic guidance.
Benefits of Ultrasound Guidance
Ultrasound offers several advantages:
- Direct visualization of nerves and blood vessels
- Reduced risk of vascular injury
- Greater procedural accuracy
- No radiation during nerve identification
The authors concluded that ultrasound made nerve localization technically easier while fluoroscopy confirmed final needle position.
Evidence Supporting Genicular Nerve RFA After Knee Replacement
The article presents a single-patient case report evaluating genicular nerve radiofrequency ablation for chronic pain after total knee replacement.
Patient Summary
- Persistent severe pain one year after knee replacement
- Conservative treatments had failed
- Implant loosening excluded
- Successful diagnostic nerve block
- Underwent genicular nerve RFA
Outcomes
Following radiofrequency treatment:
- Pain score reduced from 9/10 to 0/10 at two weeks.
- Pain remained 0/10 at three months, increasing only to 3/10 after physical therapy.
- Knee range of motion improved.
- Functional ability, including stair climbing, improved.
- Knee Injury and Osteoarthritis Outcome Score (KOOS) also improved significantly.
The authors concluded that this successful case supports further prospective and randomized studies evaluating genicular nerve radiofrequency ablation for persistent pain after total knee replacement.
Who May Benefit?
Genicular nerve RFA may be considered in patients who:
- Have persistent pain after TKA
- Have no evidence of infection
- Have stable implants
- Have failed medications and physiotherapy
- Respond positively to diagnostic nerve blocks
- Are poor candidates for revision surgery
Advantages of Genicular Nerve RFA
- Minimally invasive
- Daycare procedure
- No large incision
- Reduced need for pain medications
- Improved walking ability
- Better quality of life
- Can delay or avoid revision surgery in selected patientsLimitations
Although promising, radiofrequency ablation is not suitable for every patient.
It will not correct:
- Loose implants
- Mechanical instability
- Prosthetic infection
- Major alignment problems
A thorough orthopedic and pain medicine evaluation remains essential.
When Should You See a Pain Specialist?
Consult an interventional pain specialist if:
- Pain persists beyond three months after surgery.
- X-rays appear normal but pain continues.
- Pain medications provide little relief.
- You wish to avoid repeat surgery.
- Your orthopedic surgeon has ruled out implant-related complications.
Frequently Asked Questions
Can knee pain return after successful knee replacement?
Yes. Persistent pain may result from nerve injury, scar tissue, soft tissue disorders, or other non-mechanical causes.
Is radiofrequency ablation painful?
No. The procedure is performed under local anesthesia with or without mild sedation.
Will it damage knee movement?
No. The procedure targets sensory nerves responsible for pain and does not affect muscle strength.
How long does relief last?
Many patients experience relief lasting several months to over a year, although outcomes vary and repeat treatment may sometimes be required.
Is the procedure safe?
When performed under ultrasound and fluoroscopic guidance by experienced specialists, genicular nerve RFA has a favorable safety profile.
Conclusion
Persistent pain after total knee replacement is a challenging but treatable condition. After excluding infection, implant loosening, and mechanical problems, genicular nerve radiofrequency ablation offers a promising minimally invasive option for carefully selected patients.
The case report you provided demonstrated marked pain reduction and functional improvement following diagnostic genicular nerve block and radiofrequency ablation, supporting further research into this technique. While larger clinical studies are needed, the findings suggest that genicular nerve RFA can be an effective option for chronic pain after knee replacement in appropriately selected patients.