Indian Journal of Pain

: 2019  |  Volume : 33  |  Issue : 3  |  Page : 121--125

Persistent postarthroplasty knee pain

Rajesh Gupta 
 Department of Anaesthesia and Pain Management, Frimley Park Hospital, Camberley, London, England, UK

Correspondence Address:
Dr. Rajesh Gupta
Frimley Park Hospital, Frimley, Camberley GU16 7UJ, London, England


Knee arthroplasty is done to relieve pain. The procedure itself can cause long lasting pain which can significantly decrease the quality of life and mobility. The factors leading to pe rsistent pain relate to patient and surgery and the management of pain before and after the surgery. The management of persistent arthroplasty pain is multidisciplinary and involves conservative and interventional pain medicine.

How to cite this article:
Gupta R. Persistent postarthroplasty knee pain.Indian J Pain 2019;33:121-125

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Gupta R. Persistent postarthroplasty knee pain. Indian J Pain [serial online] 2019 [cited 2020 Apr 1 ];33:121-125
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Knee arthroplasty is done to improve mobility and decrease pain. It provides good pain relief though up to 20% patients complain of persistent pain.[1] Revision surgery may help to a certain extent in treating the pain, but it should be performed early (within 2–5 years) to achieve better results.[2] This article will look at the factors involved with persistent pain in knee arthroplasty and its management.

Clinical anatomy

The knee is a hinge joint between the tibia and the femur with the patella placed anterior and slightly superior to the joint. The patella protects the front of the joint and increases the force of action of the quadriceps femoris by increasing the angle of action. The four major ligaments are the anterior cruciate ligament, posterior cruciate ligament, tibial collateral ligament, and fibular collateral ligament. The menisci, which are located medially and laterally, correct the lack of congruence between the articular surface of tibia and femur and improve weight distribution. They do not contain pain-sensitive structures and are insensitive to trauma. The capsule connects the distal end of the femur with the proximal border of the tibia. The main movements of the knee are flexion and extension while internal and external rotation of the tibia in relation to femur is a secondary action and possible only with a flexed knee.

The saphenous nerve, the femoral nerve, the obturator nerve, and sensory branches of the tibial nerve supply the knee. Genicular nerves supply the anterior knee. The superolateral branch originates from the nerve to the vastus lateralis and supplies superolateral anterior aspect of the capsule. The superomedial branch originates from the nerve to the vastus medialis and supplies the anteromedial aspect of the capsule. The middle branch is a continuation of the nerve supplying vastus intermedius and reaches the suprapatellar pouch of the knee capsule. The inferolateral branch arises from the common peroneal nerve and supplies around the fibular head. The inferomedial branch is from the saphenous nerve and runs on the medial side of the knee along the medial condyle and the shaft. The lateral branch of the common peroneal nerve distributes around the lateral aspect of the capsule.

The infrapatellar fat pad is located under the patellar ligament and contains nociceptors. The bursae surround the knee and include prepatellar bursa, superficial and deep infrapatellar bursa, popliteal bursa, and suprapatellar bursa.


The surgery involves longitudinal midline incision cutting across the deep fascia, retinacular ligaments, and capsule. The synovial membrane is opened and access to menisci, ligaments and cartilages are obtained. The painful stimuli to synovium are poorly localized while the capsule and periosteum produce sharp pain. The cartilages adjacent to the bone have no nociceptors.

The surgical procedure produces inflammation causing an increase in prostaglandins (PGs), especially PGE2, which is implicated in postoperative pain. The mediators include histamine and bradykinin and excitatory amino acids. Spinal cord stimulation leads to the production of glutamate and substance P in the dorsal horn. Glutamate activates N-methyl-D-aspartate (NMDA) receptors causing long-lasting changes in the dorsal horn neurons. Expression of certain genes such as c-fos, nitric oxide synthase, and cyclooxygenase 2 leads to peripheral and subsequent central sensitization. The balanced analgesic techniques target these mediators and provide analgesia.

The major risk factors for knee pain after arthroplasty include preoperative pain severity, poor mental health, pain catastrophizing, and the presence of patient comorbidities.[3] Even though knee arthroplasty removes the nociceptive input from the joint, the persistence of pain indicates the presence of central sensitization. The surgical factors involved with persistent pain include infection, instability, misalignment, soft-tissue impingement, recurrent hemarthrosis, and extensor mechanism problems (patellar maltracking and nonresurfaced patella).[4] Catastrophizing is exaggerated negative perception of the pain and its management. It is the strongest risk factor, and a high preoperative pain catastrophizing scale has been associated with both acute and chronic pain, deficient central nociception, and reduction in function. Preexisting heart disease has been found to be an independent risk factor for pain at 5 years after primary knee arthroplasty. The peripheral edema seen may contribute to the lower-extremity pain. Similarly, anxiety predisposes to pain 2–5 years after the arthroplasty. Other causes of persistence pain include younger age, female gender, and severe preoperative pain.[5] Arthroplasty is a potent stimulator of both sympathetic system and pituitary axis. Higher levels of epinephrine at a 1-month follow-up are associated with more pain at 3 months. Patients with high heart rate immediately before the surgery are associated with more postoperative pain. Sedentary patients before the surgery have low levels of urinary cortisol and that can predict the increased postoperative pain. These patients are less likely to engage with physical therapy after the surgery and thus report more postoperative pain and later persistent pain.[6] These patients also have lower muscle mass in the legs. Periarticular muscles provide structural stability and support to degenerated knees, and the loss in volume may increase the pain sensation.

Clinical features and diagnosis

The patient may present with generalized pain. A history may elicit the probable reason for the pain. Pain on weight-bearing indicates tibiofemoral involvement, whereas the pain related to stairs main indicates patellofemoral involvement. Pain on the activity instead of at rest indicates irritation of soft tissues or mechanical impingement. On the other hand, pain at rest may indicate infection or neuroma.

Neuropathic pain may be seen. The features include electrical shock sensation and burning sensations. Unpleasant sensations seen are paresthesia, dysesthesia, itching, and numbness.

Examination of the knee should involve the gait and any instability. The anatomy should be compared on both sides. Local examination should focus on erythema, swelling, and discharge if any. Any previous scars, draining sinuses, and pigment changes should be noted. The knee may show signs and symptoms of complex regional pain syndrome such as loss of hair, skin discoloration, and shiny appearance of the skin. Palpation of the knee may indicate pain if neuroma is present. The patella should be palpated, and tracking of the patella should be done. Abnormal tracking may mean malalignment, excessive medialization, or overstuffing of the patellofemoral joint. Extension instability and flexion instability as part of the procedure may lead to pain.[7] The ipsilateral hip, ankle, and lumbar spine should be examined.

Diagnostic evaluation should include serological tests. Erythrocyte sedimentation rate will rise about 5 days after the surgery and will normally decline by 3 months back to the preoperative levels. C-reactive protein peaks at 2 days and comes back to normal by 3 weeks. It is a more specific marker of infection. Interleukin-6 (IL-6) is a better marker of infection and levels increase within 12 h and comes back to normal within 3 days. Patients with raised markers should have synovial fluid aspiration to exclude infection.

Tests for allodynia and hyperalgesia should be done. Douleur Neuropathique 4 questionnaire is a quick screening test for neuropathic pain.


It involves a multidisciplinary approach and involves optimum and preoperative and perioperative management in arthroplasty. This includes adequate management of preoperative pain and decrease in risk factors such as psychological and cognitive disturbances, multimodal analgesia, and patient education. The evidence is limited with these interventions with regard to persistent pain.

 Preoperative Period

Pain after the total knee arthroplasty is severe in up to 60% of patients and will affect early mobilization. The painful stimuli cause a recruitment effect by hyperpolarization of the neurons. The usage of preemptive analgesia is used to prevent this amplification and subsequent sensitization. The analgesia is administered before the painful stimulus and extends to the intraoperative and postoperative period. Preoperative use of nonsteroidal anti-inflammatory drugs (NSAIDs) reduces the pain. The use is limited because of associated effects such as decrease in platelet aggregation, renal impairment, delayed wound healing, and increase in bleeding time.

Cycloxygenase-2 (COX-2) inhibitors selectively inhibit COX-2 enzyme that is an important mediator of peripheral and central sensitization. The administration before the surgery reduces the postoperative consumption of opioids without a significant increase in postoperative bleeding. Preoperative administration also prevents flare-up of the arthritic pain preoperatively, which is an independent risk factor for severe postoperative pain, prolonged hospital stay, and decreased range of movements. It is recommended to continue the COX-2 inhibitors for at least up to 2 weeks after the surgery to cover the duration of surgical inflammatory process. A combination of acetaminophen with NSAIDs provides superior analgesia than either drug alone.

Persistent pain after the arthroplasty may have an element of neuropathic pain. Anticonvulsants such as gabapentin and pregabalin have shown some benefit if administered before the surgery. The mechanism is the modulation of central pain pathways by binding to alpha-2-delta subunit of voltage-gated calcium channels. Perioperative pregabalin in a dosage of 300 mg helps in decreasing opioid consumption and increased range of motion when continued up to 14 days after the operation.[8] The reduction in neuropathic pain can be seen up to 6 months. Ketamine is an NMDA receptor antagonist which when given along with opioids reduce the total opioid consumption and the incidence of persistent pain.[9]

 Intraoperative Period

Nerve blocks have been found useful to decrease postoperative pain. The other benefits include decrease in deep-venous thrombosis, pulmonary embolism, blood transfusion requirements, and postoperative pneumonia. The nerve blocks can be divided according to the blockade of pain from the anterior nerve group than the posterior nerve group.

The femoral triangle is an anatomical space in the upper third of the thigh. It is present below the inguinal ligament and extends up to the halfway point between the anterior superior iliac spine and patella. Blockade of nerves in the femoral triangle provides good analgesia after total knee arthroplasty with a medial incision. This involves blockade of the infrapatellar nerve of the saphenous nerve, medial retinacular nerve (branch of nerve to vastus medialis), and medial femoral cutaneous nerve.[10] This block has been found to be as effective as compared to the femoral nerve block.[11] If the incision is lateral, a combined femoral and sciatic nerve block will reduce pain and reduce analgesic demand. This comes at the risk of decreased ambulation which is undesirable.

Adductor canal is present where the medial border of the sartorius muscle intersects the medial border of the adductor longus. The canal can be visualized under ultrasound by visualizing the vasoadductor membrane. It provides analgesia equivalent to femoral nerve block with less motor block and early ambulation.[12] Adductor canal block may not provide analgesia on the medial side because injection into the adductor canal does not block the nerve to the vastus medialis as it is superficial to the vasoadductor membrane. The posterior knee pain can be treated with infiltration of local anesthetic which has not been found superior to the sciatic nerve block. The origin of the pain is not from the capsule as it is not altered during the surgery but from the intra-articular innervation. If the surgery has been done to release the hamstring contracture, the pain will respond to the sciatic nerve block. Obturator nerve block done along with blockade in the femoral triangle decreases the morphine requirements.[13]

Sciatic nerve block has efficacy when used along with the femoral nerve block for complete analgesia after knee arthroplasty. There are concerns regarding the motor and sensory effects, limiting its usage, as early ambulation is required. It may also prevent the early diagnosis of perioperative nerve injury, the incidence of which is up to 10%. It is seen that continuous peripheral nerve blocks are associated with decreased motor strength and sensory ability, thus increasing the risk of falls. The effects can be minimized using single-injection blocks and use of ropivacaine. The duration of action of bupivacaine is 2–3 times that of ropivacaine and thus allows for better titration if an infusion is used.[14] A new peripheral nerve procedure has been used to anesthetize the posterior portion of the knee. Local anesthetic is deposited in the interspace between the popliteal artery and the capsule of the posterior knee (iPACK block (Infiltration between polipteal artery and the capsule of the knee)). The block spares the main trunk of the tibial and peroneal nerves and blocks the terminal branches of the posterior knee joint.

Neuraxial blocks have been used, and epidural analgesia has been the mainstay for some time. It is associated with complications, which may prevent early mobilization such as urinary retention, hypotension, and pruritus. The evidence is more in favor of regional nerve blocks than neuraxial blocks.[15]

A major proportion of the pain originates from the joint and surgical wound. Infiltrative techniques involve local anesthetic administration into the surgical site. A cocktail of medications (ropivacaine, epinephrine, ketorolac, and clonidine) up to a maximum of 100 ml provides effective postoperative analgesia. The efficacy is increased by using a small gauge needle (22G) and the administration of the cocktail near the most sensitive tissues (periosteum, posterior capsule, and the fat pad).[16] Liposomal bupivacaine is a long-acting formulation of bupivacaine. It has shown benefit in infiltration and may decrease the incidence of quadriceps femoris weakness and may decrease the risk of falls after the surgery. The analgesic effect of liposomal bupivacaine has not been shown to be better than unencapsulated bupivacaine.[17] Wound catheter infusion techniques improve analgesia, decrease opioid requirement, and reduce hospital stay.[18]

 Persistent Pain

The management is based on biopsychosocial model. Most often, absolute pain reduction is not the aim. The aim should be for the improvement in function and quality of life. It is seen that 18.2% of the patients are not satisfied with the outcome of total knee arthroplasty, usually because of the pain.[19]

The initial management is to assess and diagnose any surgically correctable causes of persistent pain. Most common surgical causes include painful neuromas, patellofemoral instability, rupture of patellar or quadriceps tendon, periprosthetic fracture of the patella, impingement syndromes, and recurrent hemarthrosis. The neuroma of the infrapatellar branch of the saphenous nerve is a common cause of persistent pain. This is seen more with classic medial parapatellar incision as compared to straight midline incision. The neuroma can be injected with local anesthetic to confirm the diagnosis and excised. If excision is not possible, selective denervation of the neuroma may help with the pain. Hypersensitivity may be a side effect which is mostly self-limiting. Knee stiffness after the surgery may present as persistent pain. The incidence is between 3% and 60%.[20] This may cause pain and functional limitation. The treatment options are intense physiotherapy, arthroscopy, or a revision of the procedure.


There is little evidence that opiates improve either function or quality of life. Weak opioids are preferred as compared to strong opioids because of the side effect profile. If the pain persists despite stronger opioids, this indicates that opioids are not useful and should be stopped.

Neuropathic pain is seen due to nerve injury. It is seen up to 13% of patients after the arthroplasty. It is more common with total and medial knee arthroplasty and rare with anterolateral approach. It may present as dysesthesia, allodynia, hyperalgesia, and spontaneous pain. Lidocaine patches have some efficacy in the management of local dysesthesia. Capsaicin ointment and subsequently capsaicin patches applied every 3 months can be beneficial. It works by releasing substance P from peripheral nerve endings. This decreases the sensitization but can cause burning or rashes. Intra-articular injections can be tried, and the mechanism of action includes decrease in inflammatory markers, PG, and interleukin secretion. Injection of botulinum A toxin shows good benefit at 2 months.[21] It produces the presynaptic block of acetylcholine release causing weakness of muscle contraction. This may restore the imbalance between muscle contractions to relieve pain. Transcutaneous electrical nerve stimulation is helpful and can be used several times a day.

If these interventions do not help, then tricyclic antidepressants should be tried such as amitriptyline and nortriptyline. The side effects include dry mouth, blurriness of the vision, drowsiness, and postural hypotension. The drugs have antidepressant effects and may decrease the anxiety and depressive components of the pain. If they are not tolerated well, a trial of anticonvulsants can be given and these include gabapentin and pregabalin. Pregabalin has a better side effect profile and needs twice-daily administration. Gabapentin if used should be stopped gradually as sudden stoppage can precipitate convulsions.

Interventional pain management includes genicular nerve block. Successful blockade can be a predictor of success for radiofrequency ablation. Six genicular nerves provide innervation to the knee, of which four are clinically accessible (superomedial, intermediate, superolateral, and inferomedial). The intermediate nerve also contributes to the prepatellar plexus. They arise in the popliteal fossa and accompany their corresponding arteries. The nerves are seen around the junction of epiphysis and metaphysis. The nerve block can be done under fluoroscopy or ultrasound. The patient is placed supine or lateral decubitus position with the affected lower extremity exposing a medial aspect of the knee. A high-frequency linear transducer is mostly applied and moved up and down to find the anatomical region where the shaft of the femur meets the medial femoral epicondyle. The artery can be visualized, and the area next to the artery is the target.[22] Radiofrequency treatment involves passing the current percutaneously with an insulated needle that has an active tip [Figure 1]. The current flows through the body tissue which acts as a resistor. Continuous passage of current heats the nerve fibers and results in Wallerian degeneration. The ablation is done at 70°–80° for up to 90 s. Pulsed radio frequency is a variation where the machine cuts off the heating as soon as the temperature reaches 41°. Tissues are exposed to electric field which leads to expression of c-fos gene in lamina I and II of the dorsal horn. Pain reduction of up to 12 weeks may be observed. The efficacy and duration may be increased with the usage of thicker needles or by doing dual radiofrequency.{Figure 1}

Water-cooled radiofrequency treatment has been used which allows water to circulate to the interior of the electrode surface avoiding the water to reach boiling temperature. This allows delivery of more energy thus causing a larger lesion. Larger lesion may increase the duration of pain relief. Preoperative radiofrequency ablation of genicular nerves has not been shown to prevent postoperative persistent pain.

If the genicular nerves are difficult to visualize because of postsurgical deformed anatomy, the pulsed radio frequency of dorsal root ganglion at the lumbar level may help the knee pain. Infrapatellar branch of the saphenous nerve is involved sometimes and is a source of neuropathic pain on the anteromedial side of the knee. Apart from conservative management, selective denervation may give relief to the patient.

Peripheral subcutaneous field stimulation has been shown to improve walking distance after the knee arthroplasty. It involves implantation of four subcutaneous neuromodulation leads subcutaneously and tunneled out through two ports on the medial and the lateral side. Peripatellar soft tissues contain substance P nociceptive fibers, and infrapatellar fat pad excision may contribute to the pain. Circumferential electrocautery and patellar denervation can desensitize and block pain receptors thus reducing the pain.[23] This has shown evidence in knees where patellar resurfacing was not done.


Persistent postarthroplasty knee pain is quite troublesome, and multimodality treatment is required for the management.

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Conflicts of interest

There are no conflicts of interest.


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