Diagnosis, Management, and Treatment of Complex Regional Pain Syndrome after Total Knee Arthroplasty: A Systematic Review and Qualitative Assessment

Introduction

Methods

Results

Study Characteristics and Demographics

The methods and results of the study selection process are shown in Figure 1. In total, 32 potential studies were assessed for eligibility, of which 15 articles published between 1985 and 2022 were included.[13,17,18,19,20,21,22,23,24,25,26,27,28,29,30] These 15 studies consisted of 6 case reports, 2 case series, 4 prospective cohorts, and 3 retrospective cohort studies. Study characteristics and assessment are shown in Table 1.[13,17,18,19,20,21,22,23,24,25,26,27,28,29,30] The average Newcastle-Ottawa score for cohort studies was 8.7 out of 9. The average compliance to CARE guidelines was 28.5/30. The 15 studies totaled 125 CRPS TKAs with a mean age of 64 $\pm$ 7 years and female-to-male ratio of 2:1.1. Mean follow up was 16.9 $\pm$ 15.9 months and ranged from 1 to 120 months. The incidence of CRPS-affected TKAs was 2.8% (95% CI: 2.25% - 3.45%), after excluding all case reports and Cameron and O’Brien et al who did not report on total number of TKAs.[20,25] All studies described CRPS in the absence of nerve injury (CRPS-I) with the exception of Rommel et. al. who described CRPS-II secondary to injury of the infrapatellar branch of the saphenous nerve.[26]

Figure 1. Preferred Reporting Items for Systematic Reviews (PRISMA) 2020 flow diagram. CRPS, complex regional pain syndrome.

Figure 1. Preferred Reporting Items for Systematic Reviews (PRISMA) 2020 flow diagram. CRPS, complex regional pain syndrome.

Table 1. Study evaluations and demographics. ^†Bruehl 2022 compared incidence at 6 weeks and 6 months; 6 months is shown here. ^‡Patient sex calculated from Bruehl’s statement that “nearly 2/3 patients were female.” ^§Jacques et al follow up reported as 12 months minimum. (/) represents lack of reported value. NOS, Newcastle-Ottawa Scale. CARE, Case Report guidelines. TKA, total knee arthroplasty. CRPS, complex regional pain syndrome. IASP, international association for the study of pain.

Table 1. Study evaluations and demographics. ^†Bruehl 2022 compared incidence at 6 weeks and 6 months; 6 months is shown here. ^‡Patient sex calculated from Bruehl’s statement that “nearly 2/3 patients were female.” ^§Jacques et al follow up reported as 12 months minimum. (/) represents lack of reported value. NOS, Newcastle-Ottawa Scale. CARE, Case Report guidelines. TKA, total knee arthroplasty. CRPS, complex regional pain syndrome. IASP, international association for the study of pain.

Author	OCEBM Level of Evidence	NOS Score	CARE Score	Number of TKAs	Number of CRPS TKAs	M/F	Age (years)	Incidence	Diagnostic Criteria	Follow up (months)
Bruehl 2022	Prospective cohort (III)	9	/	110.0	14.0	F (9:5) ‡	/	12.7%†	2012 IASP	6
Burns 2006	Retrospective cohort (III)	9	/	1280.0	8.0	F (6:2)	68.0	0.6%	2012 IASP	46 (16-74)
Harden 2003	Prospective cohort (III)	9	/	77.0	7.0	/	/	9.1%	2012 IASP	6
Jacques 2021	Prospective cohort (III)	9	/	469.0	46.0	/	/	9.8%	Budapest Criteria + three-phase bone scintigraphy	12§
Kosy 2018	Prospective cohort (III)	9	/	100.0	0.0	/	/	0.0%	Budapest Criteria	3
Nielsen 1985	Retrospective cohort (III)	8	/	247.0	3.0	/	/	1.2%	/	24
O'Brien 1995	Retrospective cohort (III)	8	/	/	7.0	/	/	/	Pain + vasomotor + sympathetic block	24
Katz 1986	Case series (IV)	/	28/30	662.0	5.0	F (4:1)	57 (44-69)	0.8%	Pain + delayed functional recovery + knee stiffness + sympathetic block	35 (18-45)
Braverman 1998	Case report (IV)	/	29/30	1.0	1.0	F	75.0	/	Pain + edema + vasomotor + knee stiffness	1
Cameron 1994	Case series (IV)	/	29/30	/	29.0	F (17:12)	63 (44-88)	/	Pain + absence of overt sepsis or implant loosening	/
Rommel 2009	Case report (IV)	/	26/30	1.0	1.0	F	96.0	/	Pain + sensory impairment	/
Royeca 2019	Case report (IV)	/	29/30	1.0	1.0	F	69.0	/	Pain + altered cutaneous sensation + knee stiffness + absence of any mechanical issues with TKA	5
Sagoo 2021	Case report (IV)	/	29/30	1.0	1.0	M	38.0	/	Pain + autonomic changes + discoloration + edema + sympathetic block	120
Söylev 2016	Case report (IV)	/	29/30	1.0	1.0	F	67.0	/	Budapest Criteria	12
Urits 2019	Case report (IV)	/	29/30	1.0	1.0	M	71.0	/	Pain + preserved strength + absence of orthopedic aberrancy	7
TOTAL		8.7 (avg)	28.5 (avg)	2951.0	125.0	F (20:11)	64$\pm$7 (avg)	2.8% (avg)		16.9$\pm$15.9 (avg)

Symptoms

A total of 11 studies totaling 69 CRPS TKAs were available for evaluation of patient symptoms.[17,18,19,20,21,26,27,28,29,30,31] Symptom incidence is depicted in Table 2 and expanded in Supplemental Table S1. Average time from surgery to CRPS diagnosis was 7 $\pm$ 3.4 months (95% CI: 6.28 – 7.72) (n=86). Hyperalgesia and allodynia were the most commonly reported symptom with an overall incidence of 62% (43/69) (95% CI: 50.9% - 73.8%) and 59% (41/69) (95% CI: 47.8% - 71.0%), respectively. The majority of pain was described by patients as ‘burning’, ‘numbness’, and ‘sharp’ sensation localized to the knee but not following any dermatome or myotome.[26,27,28,29,30,31] There was no pattern to pain location; reports ranged from anterior,[30,31] to posterolateral,[27] anterolateral,[26] global, [31] or involvement of the ankle or upper extremities.[28,29] Vasomotor symptoms, including skin temperature and color changes, were present in 37% (26/69) (95% CI: 26.2% - 49.1%) and 11% (8/69) (95% CI: 4.0% - 19.1%) of all CRPS TKAs. Sudomotor symptoms, including edema and sweating, were explicitly mentioned in 17% (95% CI: 8.4% - 26.3%) and 1.4% (95% CI: 0.0% - 11.3%) of all CRPS TKAs, respectively. Lastly, motor symptoms (defined as weakness, stiffness, or limitation of range of motion (ROM)) were seen in 32% (22/69) (95% CI: 20.9% - 42.9%) of cases while trophic changes were seen in 5.7% (4/69) (95% CI: 0.3% - 11.3%) of cases.

Table 2. Symptoms and physical exam findings. Cumulative incidence is defined as number of positive findings divided by total number of CRPS TKA. Relative incidence is defined as number of positive findings divided by number of CRPS TKA that mention that finding (positive or negative). Motor symptoms reported as positive for either limited ROM or weakness. Trophic changes reported positive for hair or nail changes. CRPS, complex regional pain syndrome. TKA, total knee arthroplasty. ROM, range of motion.

Table 2. Symptoms and physical exam findings. Cumulative incidence is defined as number of positive findings divided by total number of CRPS TKA. Relative incidence is defined as number of positive findings divided by number of CRPS TKA that mention that finding (positive or negative). Motor symptoms reported as positive for either limited ROM or weakness. Trophic changes reported positive for hair or nail changes. CRPS, complex regional pain syndrome. TKA, total knee arthroplasty. ROM, range of motion.

	Symptoms			Physical Exam Findings
Category	Symptom	Incidence (cumulative)	Incidence (relative)	Finding	Incidence (cumulative)	Incidence (relative)
Pain	Hyperalgesia	62% (43/69)	62% (43/69)
	Allodynia	59% (41/69)	61% (41/67)
Vasomotor	Skin Temp	37% (26/69)	44% (26/59)	Skin Temp	50% (20/40)	76.9% (20/26)
	Color	11% (8/69)	26% (8/31)	Color	17.5% (7/40)	22.6% (7/31)
Sudomotor	Edema	17% (12/69)	92% (12/13)	Edema	72.5% (29/40)	85.3% (29/34)
	Diaphoresis	1.4% (1/69)	1.8% (1/55)	Diaphoresis	0% (0/40)	0% (0/21)
Motor	Stiffness	32% (22/69)	96% (22/23)	Change in ROM	62.5% (25/40)	78.1% (25/32)
				Weakness	22.5% (9/40)	52.9% (9/17)
Trophic	Trophic	5.7% (4/69)	7% (4/57)	Trophic	7.5% (3/40)	15% (3/20)

Diagnosis, Treatment, and Prognosis

Nine studies totaling 48 CRPS TKAs (38%) were available for evaluation of diagnosis, treatment, and outcomes.[17,19,20,26,27,28,29,30,31] (Supplemental Table S3). 7 CRPS TKA patients underwent diagnostic lumbar sympathetic block.[17,30,31] Two cases utilized a bone scan, both of which revealed non-specific increased periprosthetic uptake.[17,28] Plain radiography identified periprosthetic osteopenia in one case,[17] although several others showed no radiographic changes.[26,27,29,30,31]

With regard to treatment, the most commonly employed modality was sympathetic block (75%, 36/48), followed by physical therapy (33%, 16/48), pharmacotherapy (27%, 13/48), and manipulation under anesthesia (25%, 12/48). A small minority of papers described use of sympathectomy or spinal stimulator (2%, 2/48).[28,30,31] The average ROM at final follow-up was 3.4° $\pm$ 3.4° extension (95% CI: 1.5° – 5.3°) to 93.2° $\pm$ 7.9° flexion (95% CI: 88.7° – 97.7°) (n=12). A total of twelve patients underwent manipulation under anesthesia (MUA). We calculated an average increase in flexion of 29$°$ (95% CI: 25.0$°$ - 33.0$°$) after MUA (n=6). Outcomes varied from continued CRPS symptoms to complete resolution. A total of 33% (95% CI: 20.0% - 46.7%) (16/48) of patients were asymptomatic at final follow up.[20,29,30,31] The remainder of cases ranged from significant reduction of symptom, intermittent symptoms, moderate pain when weightbearing, to continued chronic pain and regret of TKA. (Table 3)

Table 3. Prognosis of CRPS after TKA. Excellent was defined as complete resolution of CRPS symptoms or qualifying knee score. Good was defined as significant improvement or qualifying knee score. Fair was defined as continued symptoms with partial improvement. Poor was defined as continuance of symptoms with minimal improvement and/or flexion < 90°, or qualifying knee score. CRPS, complex regional pain syndrome. TKA, total knee arthroplasty.

Table 3. Prognosis of CRPS after TKA. Excellent was defined as complete resolution of CRPS symptoms or qualifying knee score. Good was defined as significant improvement or qualifying knee score. Fair was defined as continued symptoms with partial improvement. Poor was defined as continuance of symptoms with minimal improvement and/or flexion < 90°, or qualifying knee score. CRPS, complex regional pain syndrome. TKA, total knee arthroplasty.

Outcome	Frequency	Definition
Excellent	25% (12/48)	- “Complete and permanent relief of symptoms” (n=9, Cameron et al 1994) - Hungerford knee score > 90/100 (n=1, Katz et al 1989) - Completely asymptomatic (n=1, Soylev et al 2016) - “Complete resolution of symptoms and wean from opioids” (n=1, Urits et al 2019)
Good	31% (15/48)	- Mean KSS score reported within “good” reference range based on Munoz 2022 validation of KSS (n=8, Burns et al 2006) - “Complete and permanent relief of CRPS symptoms [but] continued patellofemoral aching with stairs” (n=3, Cameron et al 1994) - “Complete and permanent relief of CRPS symptoms [but] somewhat lax knee” (n=1, Cameron et al 1994) - Hungerford knee score 8089/100 (n=1, Katz et al 1989) - Hungerford knee score 8089/100 (n=1, Katz et al 1989) - “Significant relief of symptoms” (n=1, Rommel et al 2009)
Fair	27% (13/48)	- “Complete or partial relief that was not permanent” (n=12, Cameron et al 1994) - “Intermittent symptoms well managed with spinal cord stimulator and pain medications” (n=1, Sagoo et al 2021)
Poor	17% (8/48)	- “Continued moderate pain with weightbearing” and active flexion of 80° (n=1, Braverman et al 1998) - “No relief at all” with sympathetic blocks, block could not be performed, final ROM flexion 80° (n=4, Cameron et al 1994) - Hungerford knee score < 70 (n=2, Katz et al 1989) - “Slight improvement in pain, continued to struggle with CRPS, regretted TKA” (n=1, Royeca et al 2019)

Discussion

Diagnosis

CRPS may be underdiagnosed after TKA due to diagnostic difficulty and overlapping symptoms with post-operative inflammation and other conditions (Table 4). From this review, persistent edema was the most characteristic sign of CRPS. Harden et al. found the most distinguishing signs to be edema, color changes, and hyperalgesia/allodynia by 6 months,[21] while Bruehl et al.’s reported edema, temperature changes, and motor changes.[18] Compared to non-CRPS TKAs with persistent pain, CRPS patients also self-report greater levels of depression and anxiety at one and six months postoperatively, respectively.[21]

Diagnostic sympathetic block can be a useful adjunct to clinical signs and symptoms.[37] From this review, 7 CRPS TKA patients underwent diagnostic sympathetic block. All 7 patients had a positive diagnostic result, defined as transient relief of symptoms with rise in skin temperature. Katz et. al.’s patients underwent sympathetic block at 7 months from surgery and 2 months from time of CRPS suspicion.[31]

There is limited need for radiography or scintigraphy. CRPS can exhibit radiological subchondral osteopenia in the patella.[37]^,[38,39] However, these findings are inconsistent and can be difficult to interpret after TKA.[13] As such, only one case demonstrated periprosthetic osteopenia,[17] with many others showing no radiographic changes.[26,27,29,30,31] Several studies have reported 80% sensitivity and 72% specificity of scintigraphy for CRPS of the knee.[40]^,[41] Katz et. al. reported only 61% of CRPS TKAs had positive bone scans.[13] However, interpretation remains difficult due to concurrent TKA prosthesis uptake.[31] Lastly, thermography is often employed as a supplementary test to support the clinical diagnosis of CRPS due to its relatively high sensitivity (76%) and specificity (93%).[37,42] However, no studies in this review used thermography.

Table 4. Differential diagnosis of CRPS after TKA.

Table 4. Differential diagnosis of CRPS after TKA.

Differential Diagnosis for TKA Complicated with CRPS
Intraarticular Causes	Extraarticular Causes
Post-operative inflammation Surgical Errors o Malpositioning o Incorrect component sizing o Error in soft tissue balancing Prosthetic loosening Heterotopic ossification Patellar complications o Un-resurfaced patella o Avascular necrosis o Fracture o Maltracking Arthrofibrosis Infection	Soft tissue pathologies o Pes anserine bursitis o Tendonitis o Impingement (patellar clunk) Neurologic pathologies o Sensitization from chronic arthritis o Radiculopathy o Peripheral neuropathy o Localized nerve injury o Neuroma Vascular pathologies o Lymphedema o Chronic venous insufficiency o Deep vein thrombosis Psychological somaticizing o Depression, anxiety, fibromyalgia Referred pain Instability Metal hypersensitivity

Conclusions

References

1. Eldufani, J.; Elahmer, N.; Blaise, G. A medical mystery of complex regional pain syndrome. Heliyon 2020, 6, e03329. [Google Scholar] [CrossRef]
2. Harden, N.R.; Bruehl, S.; Perez, R.S.G.M.; Birklein, F.; Marinus, J.; Maihofner, C.; Lubenow, T.; Buvanendran, A.; Mackey, S.; Graciosa, J.; et al. Validation of proposed diagnostic criteria (the "Budapest Criteria") for Complex Regional Pain Syndrome. Pain 2010, 150, 268–274. [Google Scholar] [CrossRef]
3. Ott, S.; Maihöfner, C. Signs and Symptoms in 1,043 Patients with Complex Regional Pain Syndrome. J Pain 2018, 19, 599–611. [Google Scholar] [CrossRef] [PubMed]
4. Mertz, K.; Trunzter, J.; Wu, E.; Barnes, J.; Eppler, S.L.; Kamal, R.N. National Trends in the Diagnosis of CRPS after Open and Endoscopic Carpal Tunnel Release. J Wrist Surg 2019, 8, 209–214. [Google Scholar] [CrossRef] [PubMed]
5. da Costa, V.V.; de Oliveira, S.B.; Fernandes, M.o.C.; Saraiva, R. Incidence of regional pain syndrome after carpal tunnel release. Is there a correlation with the anesthetic technique? Rev Bras Anestesiol 2011, 61, 425–433. [Google Scholar] [CrossRef] [PubMed]
6. Buller, M.; Schulz, S.; Kasdan, M.; Wilhelmi, B.J. The Incidence of Complex Regional Pain Syndrome in Simultaneous Surgical Treatment of Carpal Tunnel Syndrome and Dupuytren Contracture. Hand (N Y) 2018, 13, 391–394. [Google Scholar] [CrossRef]
7. Rewhorn, M.J.; Leung, A.H.; Gillespie, A.; Moir, J.S.; Miller, R. Incidence of complex regional pain syndrome after foot and ankle surgery. J Foot Ankle Surg 2014, 53, 256–258. [Google Scholar] [CrossRef]
8. Teichmüller, K.; Rose, N.; Dreiling, J.; Schwarzkopf, D.; Meißner, W.; Rittner, H.L.; Kindl, G. Incidence and treatment of complex regional pain syndrome after surgery: analysis of claims data from Germany. Pain Rep 2024, 9, e1210. [Google Scholar] [CrossRef]
9. Razmjou, H.; Boljanovic, D.; Wright, S.; Murnaghan, J.; Holtby, R. Association between Neuropathic Pain and Reported Disability after Total Knee Arthroplasty. Physiother Can 2015, 67, 311–318. [Google Scholar] [CrossRef]
10. Beswick, A.D.; Wylde, V.; Gooberman-Hill, R.; Blom, A.; Dieppe, P. What proportion of patients report long-term pain after total hip or knee replacement for osteoarthritis? A systematic review of prospective studies in unselected patients. BMJ Open 2012, 2, e000435. [Google Scholar] [CrossRef]
11. Hutton, B.; Salanti, G.; Caldwell, D.M.; Chaimani, A.; Schmid, C.H.; Cameron, C.; Ioannidis, J.P.; Straus, S.; Thorlund, K.; Jansen, J.P.; et al. The PRISMA extension statement for reporting of systematic reviews incorporating network meta-analyses of health care interventions: checklist and explanations. Ann Intern Med 2015, 162, 777–784. [Google Scholar] [CrossRef] [PubMed]
12. Page, M.J.; McKenzie, J.E.; Bossuyt, P.M.; Boutron, I.; Hoffmann, T.C.; Mulrow, C.D.; Shamseer, L.; Tetzlaff, J.M.; Akl, E.A.; Brennan, S.E.; et al. The PRISMA 2020 statement: an updated guideline for reporting systematic reviews. BMJ 2021, 372, n71. [Google Scholar] [CrossRef] [PubMed]
13. Katz, M.M.; Hungerford, D.S. Reflex sympathetic dystrophy affecting the knee. J Bone Joint Surg Br 1987, 69, 797–803. [Google Scholar] [CrossRef]
14. Wells, G.; Shea, B.; O'Connell, D.; Peterson, J.; Welch, V.; Losos, M.; Tugwell, P. The Newcastle-Ottawa Scale (NOS) for assessing the quality of nonrandomised studies in meta-analyses. The Ottawa Hospital Research Institute, 2021.
15. Gagnier, J.; Kienle, G.; Altman, D.; Moher, D.; Sox, H.; Riley, D. The CARE Guidelines: Consensus-based Clinical Case Reporting Guideline Development. the CARE Group.
16. ACIP GRADE Handbook for Developing Evidence-based Recommendations Center for Disease Control, 2024.
17. Braverman, D.L.; Kern, H.B.; Nagler, W. Recurrent spontaneous hemarthrosis associated with reflex sympathetic dystrophy. Arch Phys Med Rehabil 1998, 79, 339–342. [Google Scholar] [CrossRef] [PubMed]
18. Bruehl, S.; Billings, F.T.; Anderson, S.; Polkowski, G.; Shinar, A.; Schildcrout, J.; Shi, Y.; Milne, G.; Dematteo, A.; Mishra, P.; et al. Preoperative Predictors of Complex Regional Pain Syndrome Outcomes in the 6 Months Following Total Knee Arthroplasty. J Pain 2022, 23, 1712–1723. [Google Scholar] [CrossRef]
19. Burns, A.W.; Parker, D.A.; Coolican, M.R.; Rajaratnam, K. Complex regional pain syndrome complicating total knee arthroplasty. J Orthop Surg (Hong Kong) 2006, 14, 280–283. [Google Scholar] [CrossRef]
20. Cameron, H.U.; Park, Y.S.; Krestow, M. Reflex sympathetic dystrophy following total knee replacement. Contemp Orthop 1994, 29, 279–281. [Google Scholar]
21. Harden, N.R.; Bruehl, S.; Stanos, S.; Brander, V.; Chung, O.Y.; Saltz, S.; Adams, A.; Stulberg, D.S. Prospective examination of pain-related and psychological predictors of CRPS-like phenomena following total knee arthroplasty: a preliminary study. Pain 2003, 106, 393–400. [Google Scholar] [CrossRef]
22. Jacques, H.; Jérôme, V.; Antoine, C.; Lucile, S.; Valérie, D.; Amandine, L.; Theofylaktos, K.; Olivier, B. Prospective randomized study of the vitamin C effect on pain and complex pain regional syndrome after total knee arthroplasty. Int Orthop 2021, 45, 1155–1162. [Google Scholar] [CrossRef]
23. Kosy, J.D.; Middleton, S.W.F.; Bradley, B.M.; Stroud, R.M.; Phillips, J.R.A.; Toms, A.D. Complex Regional Pain Syndrome after Total Knee Arthroplasty is Rare and Misdiagnosis Potentially Hazardous-Prospective Study of the New Diagnostic Criteria in 100 Patients with No Cases Identified. J Knee Surg 2018, 31, 797–803. [Google Scholar] [CrossRef]
24. Nielsen, S.; Hvid, I.; Sneppen, O. Total condylar knee arthroplasty. A report of 2-year follow-up on 247 cases. Arch Orthop Trauma Surg (1978) 1985, 104, 227–232. [Google Scholar] [CrossRef] [PubMed]
25. O'Brien, S.J.; Ngeow, J.; Gibney, M.A.; Warren, R.F.; Fealy, S. Reflex sympathetic dystrophy of the knee. Causes, diagnosis, and treatment. Am J Sports Med 1995, 23, 655–659. [Google Scholar] [CrossRef] [PubMed]
26. Rommel, O.; Finger, L.; Bös, E.; Eichbaum, A.; Jäger, G. [Neuropathic pain following lesions of the infrapatellar branch of the femoral nerve : an important differential diagnosis in anterior knee pain]. Schmerz 2009, 23, 355–359. [Google Scholar] [CrossRef]
27. Royeca, J.M.; Cunningham, C.M.; Pandit, H.; King, S.W. Complex regional pain syndrome as a result of total knee arthroplasty: A case report and review of literature. Case Rep Womens Health 2019, 23, e00136. [Google Scholar] [CrossRef]
28. Sagoo, N.S.; Sharma, R.; Alaraj, S.; Sharma, I.K.; Bruntz, A.J.; Bajaj, G.S. Metal Hypersensitivity and Complex Regional Pain Syndrome After Bilateral Total Knee Arthroplasty: A Case Report. JBJS Case Connect 2021, 11. [Google Scholar] [CrossRef] [PubMed]
29. Söylev, G.; Boya, H. A rare complication of total knee arthroplasty: Type l complex regional pain syndrome of the foot and ankle. Acta Orthop Traumatol Turc 2016, 50, 592–595. [Google Scholar] [CrossRef]
30. Urits, I.; Osman, M.; Orhurhu, V.; Viswanath, O.; Kaye, A.D.; Simopoulos, T.; Yazdi, C. A Case Study of Combined Perception-Based and Perception-Free Spinal Cord Stimulator Therapy for the Management of Persistent Pain after a Total Knee Arthroplasty. Pain Ther 2019, 8, 281–284. [Google Scholar] [CrossRef]
31. Katz, M.M.; Hungerford, D.S.; Krackow, K.A.; Lennox, D.W. Reflex sympathetic dystrophy as a cause of poor results after total knee arthroplasty. J Arthroplasty 1986, 1, 117–124. [Google Scholar] [CrossRef]
32. Taylor, S.S.; Noor, N.; Urits, I.; Paladini, A.; Sadhu, M.S.; Gibb, C.; Carlson, T.; Myrcik, D.; Varrassi, G.; Viswanath, O. Complex Regional Pain Syndrome: A Comprehensive Review. Pain Ther 2021, 10, 875–892. [Google Scholar] [CrossRef]
33. Onodera, T.; Iwasaki, K.; Matsuoka, M.; Morioka, Y.; Matsubara, S.; Kondo, E.; Iwasaki, N. The alterations in nerve growth factor concentration in plasma and synovial fluid before and after total knee arthroplasty. Sci Rep 2024, 14, 8943. [Google Scholar] [CrossRef]
34. George, S.Z.; Bolognesi, M.P.; Bhavsar, N.A.; Penrose, C.T.; Horn, M.E. Chronic Pain Prevalence and Factors Associated With High Impact Chronic Pain following Total Joint Arthroplasty: An Observational Study. J Pain 2022, 23, 450–458. [Google Scholar] [CrossRef]
35. O'Connor, M.I. Sex differences in osteoarthritis of the hip and knee. J Am Acad Orthop Surg 2007, 15 Suppl 1, S22–25. [Google Scholar] [CrossRef]
36. Pons, T.; Shipton, E.A.; Williman, J.; Mulder, R.T. Potential risk factors for the onset of complex regional pain syndrome type 1: a systematic literature review. Anesthesiol Res Pract 2015, 2015, 956539. [Google Scholar] [CrossRef]
37. Dowd, G.S.; Hussein, R.; Khanduja, V.; Ordman, A.J. Complex regional pain syndrome with special emphasis on the knee. J Bone Joint Surg Br 2007, 89, 285–290. [Google Scholar] [CrossRef]
38. Hogan, C.J.; Hurwitz, S.R. Treatment of complex regional pain syndrome of the lower extremity. J Am Acad Orthop Surg 2002, 10, 281–289. [Google Scholar] [CrossRef] [PubMed]
39. Cooper, D.E.; DeLee, J.C. Reflex Sympathetic Dystrophy of the Knee. J Am Acad Orthop Surg 1994, 2, 79–86. [Google Scholar] [CrossRef] [PubMed]
40. Kwon, H.W.; Paeng, J.C.; Nahm, F.S.; Kim, S.G.; Zehra, T.; Oh, S.W.; Lee, H.S.; Kang, K.W.; Chung, J.K.; Lee, M.C.; et al. Diagnostic performance of three-phase bone scan for complex regional pain syndrome type 1 with optimally modified image criteria. Nucl Med Mol Imaging 2011, 45, 261–267. [Google Scholar] [CrossRef] [PubMed]
41. Ringer, R.; Wertli, M.; Bachmann, L.M.; Buck, F.M.; Brunner, F. Concordance of qualitative bone scintigraphy results with presence of clinical complex regional pain syndrome 1: meta-analysis of test accuracy studies. Eur J Pain 2012, 16, 1347–1356. [Google Scholar] [CrossRef]
42. Wasner, G.; Schattschneider, J.; Baron, R. Skin temperature side differences--a diagnostic tool for CRPS? Pain 2002, 98, 19–26. [Google Scholar] [CrossRef]
43. Lewis, J.S.; Kellett, S.; McCullough, R.; Tapper, A.; Tyler, C.; Viner, M.; Palmer, S. Body Perception Disturbance and Pain Reduction in Longstanding Complex Regional Pain Syndrome Following a Multidisciplinary Rehabilitation Program. Pain Med 2019, 20, 2213–2219. [Google Scholar] [CrossRef]
44. Cooper, D.E.; DeLee, J.C.; Ramamurthy, S. Reflex sympathetic dystrophy of the knee. Treatment using continuous epidural anesthesia. J Bone Joint Surg Am 1989, 71, 365–369. [Google Scholar] [CrossRef]
45. Akhtar, M.; Razick, D.; Seibel, A.; Asad, S.; Shekhar, A.; Shelton, T. Outcomes of Early Versus Delayed Manipulation Under Anesthesia for Stiffness Following Total Knee Arthroplasty: A Systematic Review and Meta-Analysis. J Arthroplasty 2024, 10.1016/j.arth.2024.05.059, doi:10.1016/j.arth.2024.05.059.
46. Chmiela, M.A.; Hendrickson, M.; Hale, J.; Liang, C.; Telefus, P.; Sagir, A.; Stanton-Hicks, M. Direct Peripheral Nerve Stimulation for the Treatment of Complex Regional Pain Syndrome: A 30-Year Review. Neuromodulation 2021, 24, 971–982. [Google Scholar] [CrossRef]
47. Chitneni, A.; Patil, A.; Dalal, S.; Ghorayeb, J.H.; Pham, Y.N.; Grigoropoulos, G. Use of Ketamine Infusions for Treatment of Complex Regional Pain Syndrome: A Systematic Review. Cureus 2021, 13, e18910. [Google Scholar] [CrossRef] [PubMed]