Concurrent Research Around Meniscus: A Bibliometric Analysis and Review of the Top Fifty Cited Papers

Abstract

Purpose

The knowledge regarding meniscus has vastly evolved over the past few decades. The meniscus’s intact, injured, and repaired status can affect other joint structures, i.e., ligaments, articular surfaces, and overall biomechanics of the knee joint. Due to available evidence’s extensiveness, it is challenging to determine the most influential topics and the emerging trends in concurrent meniscus research. This study aims to identify the top fifty cited papers in meniscus research and concurrent knee issues and analyse their characteristics.

Methods

A comprehensive search was conducted on the Thompson Reuters Web of Science database to prepare a list of top fifty cited articles that included original articles and review articles concerning meniscus. The included articles were analysed for the source journal, investigating institution, country of the corresponding author, year of publication, total citations, annual citation rate, and a qualitative review.

Results

The search strategy resulted in 6768 original articles and 453 review articles. The top fifty cited articles were published from 1969 to 2014 and belonged to 14 journal sources. There were 43 original articles and seven review articles. The average citations per article were 417.4 and the average citations per paper per year were 22.6. Besides the meniscus, a general interest in the clinical assessment scores, anterior cruciate ligament, long-term osteoarthritis, and cartilage was observed.

Conclusion

Most of the research concerning meniscus relates to the importance of meniscus preservation, the link between meniscus injuries and concomitant anterior cruciate ligament and chondral injuries, and its role in long-term gonarthrosis. The western countries have contributed the maximum to the top-cited evidence concerning meniscus. The meniscus repair and transplantation techniques have recently gained importance and need further research to qualify for the top-cited evidence.

Introduction

The meniscus forms an integral part of the knee joint with a special role in weight transmission and shock absorption between the distal femur and proximal tibia. Besides this, it plays an additive role in the stability of the knee joint. The knee joint contains a medial and a lateral meniscus. The menisci are crescent-shaped fibrocartilaginous structures covering around 70% of the articular surface between the tibial plateau and femoral condyles. Meniscal tears are considered the most common knee injuries with a mean annual incidence of 66 per 100,000, in which medial meniscus tears are more common [1, 2]. Meniscus injuries can be sports-related, traumatic, or non-sporting activities with even mild traumatic events during normal daily activities, especially in the older age group [1, 3]. Many operative and non-operative treatment options have been advocated after considering the patient profile and the meniscal injury type [4]. The surgeons treating meniscal injuries should understand its anatomy, microarchitecture, function, biochemical and biomechanical properties.

The meniscus is not an isolated knee structure and functions with the other knee structures in providing stability and load transmission. The meniscus’s intact, injured, and repaired status can affect other joint structures, i.e., ligaments, articular surfaces, and overall biomechanics. Over the years, several studies have discussed the meniscus and its related aspects. The advancements in the treatment options for meniscal injuries and their impact on concurrent knee joint issues can help orthopaedic surgeons better manage their patients. Due to the available evidence’s extensiveness, it is challenging to determine the most influential topics and the emerging trends in concurrent meniscus research. However, knowledge about the most sought publications can help formulate new research plans and generate stronger evidence. The bibliometric analysis offers clinicians and researchers a list of the most referenced sources and helps explore and identify the major contributors among journals, institutions, and countries. The purpose of this study is to identify the top fifty most cited papers in the field of meniscus research and concurrent knee issues and analyse their characteristics.

Materials and Methods

Two authors searched the Thomson Reuters Web of Science database on 10th September 2020 using specific keywords, "meniscus", "menisci", "meniscal", "meniscectomy”, separated by the “OR” operator, and under the “topic” option. The “topic” based search is more relevant for searching concurrent interests compared to “field” based search, which provides more specific results. The search was confined to the English language articles only and without any year restriction. The results were refined using the Web of Science Categories under “ORTHOPEDICS” AND “SPORT SCIENCES” AND “SURGERY”. All journals or “source titles” falling under these categories were considered for the analysis. Only original articles and review articles based on human meniscus were considered inclusion.

Two other authors prepared a list of fifty top-cited articles by including the articles focusing on the meniscus and its disorders and those analysing the association of meniscus and its conditions with other knee disorders (Table 1). The articles not addressing the afore-stated two criteria were not included in the final list of 50 articles. Additionally, animal studies with no relevance to human meniscus were also excluded. The titles and abstracts of the search results sorted in decreasing order of citations were analysed to include the articles. The full texts were accessed to confirm the same for the articles where the abstracts did not show any relevance to the above-stated criteria. The articles not fulfilling the inclusion criteria were sequentially excluded until a list of fifty top-cited articles was achieved. The disagreement between the two researchers was resolved through mutual discussion. The top fifty articles, ranked in decreasing order of total citations, were analysed for the source journal, investigating institution, country of the corresponding author, year of publication, total citations, citations per year (annual citation rate) and qualitative review. We used the open-source Bibliometrix R-package for the data analysis. According to study types (clinical, basic science/experimental studies, scoring system, and review articles), articles were allocated manually to different categories. Clinical studies were further classified as therapeutic, prognostic, and diagnostic. Before the qualitative review, the level of evidence was assigned for all clinical articles when applicable using the Journal of Bone and Joint Surgery ranking system, updated in early 2015 [5].

Table 1.

Search strategy and analysis of articles presented in search results

Search strategy	Topic search on Web of Science: "meniscus" OR "menisci" OR "meniscal" OR "meniscectomy"
Language	English articles only
Categories	“Orthopedics” And “Sport Sciences” And “Surgery”
Article types	Original articles and review articles on human meniscus (excluding animal studies)
Criteria for ranking	Top 50 articles in decreasing order of total citations
Parameters analyzed	Source journal, level of evidence, investigating institution, country of the corresponding author, year of publication, total citations, citations per year (annual citation rate), and qualitative review
Classification of articles	1. Clinical, basic science/experimental studies, scoring system, and review articles 2. Therapeutic, prognostic and diagnostic

Results

The afore-stated keywords search yielded 20,013 results, out of which 8102 articles belonged to the predefined categories (ORTHOPAEDICS, SPORTS MEDICINE AND SURGERY). The number was further reduced to 7221 articles after excluding the literature other than original articles and review articles. There were 6768 original articles and 453 review articles. The papers were published between the years 1956 to 2020. Fourteen articles were sequentially excluded from the results sorted in decreasing citations order due to their non-relevance to the meniscus in eleven studies and due to animal experiments in three. Table 2 lists the top fifty most cited articles on meniscus research [6–55]. The number of citations ranged between 239 and 1730, and the year of publication went between 1969 and 2014.

Table 2.

Top fifty cited articles arranged in order of individual article citations

S. no	Article title	Year of publication	Number of citations	Journal
1	Knee injury and osteoarthritis outcome score (KOOS)—Development of a self-administered outcome measure [6]	1998	1730	J ORTHOP SPORT PHYS
2	The long-term consequence of anterior cruciate ligament and meniscus injuries—Osteoarthritis [7]	2007	1183	AM J SPORT MED
3	Fate of the acl-injured patient—a prospective outcome study [8]	1994	861	AM J SPORT MED
4	Whole-organ magnetic resonance imaging score (WORMS) of the knee in osteoarthritis [9]	2004	858	OSTEOARTHR CARTILAGE
5	A retrospective case–control injuries analysis of 2002 running [10]	2002	843	BRIT J SPORT MED
6	Cartilage injuries: A review of 31,516 knee arthroscopies [11]	1997	808	ARTHROSCOPY
7	Microvasculature of the human meniscus [12]	1982	603	AM J SPORT MED
8	Articular cartilage defects in 1,000 knee arthroscopies [13]	2002	519	ARTHROSCOPY
9	Meniscal tears—the effect of meniscectomy and of repair on intraarticular contact areas and stress in the human knee—a preliminary report [14]	1986	493	AM J SPORT MED
10	The effect of medial meniscectomy on anterior–posterior motion of the knee [15]	1982	491	J BONE JOINT SURG AM
11	Late results after meniscectomy [16]	1969	457	J BONE JOINT SURG AM
12	Knee osteoarthritis after anterior cruciate ligament injury a systematic review [17]	2009	457	AM J SPORT MED
13	Material properties and structure–function relationships in the menisci [18]	1990	456	CLIN ORTHOP RELAT R
14	Factors affecting late results after meniscectomy [19]	1974	447	J BONE JOINT SURG AM
15	Autologous Chondrocyte Implantation A Long-term Follow-up [20]	2010	415	AM J SPORT MED
16	Magnetic resonance imaging of articular cartilage in the knee—An evaluation with use of fast-spin-echo imaging [21]	1998	414	J BONE JOINT SURG AM
17	Development of a patient-reported measure of function of the knee [22]	1998	413	J BONE JOINT SURG AM
18	Mechanical changes in knee after meniscectomy [23]	1976	409	J BONE JOINT SURG AM
19	Biomechanical consequences of a tear of the posterior root of the medial meniscus [24]	2008	400	J BONE JOINT SURG AM
20	Knee injury and osteoarthritis outcome score (KOOS)—validation of a Swedish version [25]	1998	380	SCAND J MED SCI SPOR
21	Role of menisci in force transmission across knee [26]	1975	379	CLIN ORTHOP RELAT R
22	The osteoarthritis initiative: report on the design rationale for the magnetic resonance imaging protocol for the knee [27]	2008	365	OSTEOARTHR CARTILAGE
23	Osteoarthritis of the knee after injury to the anterior cruciate ligament or meniscus: The influence of time and age [28]	1995	360	OSTEOARTHR CARTILAGE
24	Epidemiology of athletic knee injuries: A 10-year study [29]	2006	359	KNEE
25	Articular cartilage defects: Study of 25,124 knee arthroscopies [30]	2007	350	KNEE
26	Evolution of semi-quantitative whole joint assessment of knee OA: MOAKS (MRI Osteoarthritis Knee Score) [31]	2011	338	OSTEOARTHR CARTILAGE
27	Incidence and Trends of Anterior Cruciate Ligament Reconstruction in the United States [32]	2014	329	AM J SPORT MED
28	Late degenerative changes after meniscectomy—factors affecting the knee after operation [33]	1984	326	J BONE JOINT SURG BR
29	Increase in Outpatient Knee Arthroscopy in the United States: A Comparison of National Surveys of Ambulatory Surgery, 1996 and 2006 [34]	2011	319	J BONE JOINT SURG AM
30	The epidemiology of musculoskeletal tendinous and ligamentous injuries [35]	2008	315	INJURY
31	Incidence and risk factors for graft rupture and contralateral rupture after anterior cruciate ligament reconstruction [36]	2005	299	ARTHROSCOPY
32	A prospective randomized study of 4-strand semitendinosus tendon anterior cruciate ligament reconstruction comparing single-bundle and double-bundle techniques [37]	2007	295	ARTHROSCOPY
33	Homologous meniscus transplantation—experimental and clinical results [38]	1989	292	INT ORTHOP
34	The role of the meniscus in the anterior–posterior stability of the loaded anterior cruciate-deficient knee—effects of partial versus total excision [39]	1986	279	J BONE JOINT SURG AM
35	The consequences of meniscectomy [40]	2006	279	J BONE JOINT SURG BR
36	Load-bearing mode of the knee joint—physical behavior of the knee joint with or without menisci [41]	1980	278	CLIN ORTHOP RELAT R
37	The incidence of healing in arthroscopic meniscal repairs in anterior cruciate ligament-reconstructed knees versus stable knees [42]	1992	271	AM J SPORT MED
38	The clinical importance of meniscal tears demonstrated by magnetic resonance imaging in osteoarthritis of the knee [43]	2003	263	J BONE JOINT SURG AM
39	Accuracy of diagnoses from magnetic resonance imaging of the knee—a multi-center analysis of 1014 patients [44]	1991	258	J BONE JOINT SURG AM
40	Tibiofemoral contact mechanics after serial medial meniscectomies in the human cadaveric knee [45]	2006	257	AM J SPORT MED
41	Meniscal subluxation: association with osteoarthritis and joint space narrowing [46]	1999	252	OSTEOARTHR CARTILAGE
42	Anterior cruciate ligament reconstruction and the long-term incidence of gonarthrosis [47]	1999	251	SPORTS MED
43	Knee Function and Prevalence of Knee Osteoarthritis After Anterior Cruciate Ligament Reconstruction A Prospective Study With 10 to 15 Years of Follow-up [48]	2010	247	AM J SPORT MED
44	Results of anterior cruciate ligament reconstruction based on meniscus and articular cartilage status at the time of surgery—Five- to fifteen-year evaluations [49]	2000	246	AM J SPORT MED
45	The ultrastructure and biochemistry of meniscal cartilage [50]	1990	245	CLIN ORTHOP RELAT R
46	Anterior cruciate ligament reconstruction: Bone-patellar tendon-bone compared with double semitendinosus and gracilis tendon grafts—A prospective, randomized clinical trial [51]	2004	243	J BONE JOINT SURG AM
47	Importance of the medial meniscus in the anterior cruciate ligament-deficient knee [52]	2000	242	J ORTHOP RES
48	Tunnel positioning of anteromedial and posterolateral bundles in anatomic anterior cruciate ligament reconstruction [53]	2008	241	AM J SPORT MED
49	A review of the effects of insulin-like growth factor and platelet derived growth factor on in vivo cartilage healing and repair [54]	2006	240	OSTEOARTHR CARTILAGE
50	Development of the menisci of the human knee joint—morphological changes and their potential role in childhood meniscal injury [55]	1983	239	J BONE JOINT SURG AM

AM J SPORT MED—American Journal of Sports Medicine; ARTHROSCOPY—Arthroscopy: The Journal of Arthroscopic and Related Surgery; BRIT J SPORT MED—British Journal of Sports Medicine; CLIN ORTHOP RELAT R—Clinical Orthopaedics and Related Research; INJURY—Injury: International Journal of the Care of the Injured; INT ORTHOP—International Orthopaedics; J BONE JOINT SURG AM—The Journal of Bone and Joint Surgery. American Volume; J BONE JOINT SURG BR—Journal of Bone and Joint Surgery. British Volume; J ORTHOP RES—Journal of Orthopaedic Research; J ORTHOP SPORT PHYS—Journal of Orthopaedic & Sports Physical Therapy; KNEE—The Knee Journal; OSTEOARTHR CARTILAGE—Osteoarthritis and Cartilage; SCAND J MED SCI SPOR—Scandinavian Journal of Medicine and Science in Sports; SPORTS MED—Sports Medicine

Main Information

The top fifty cited articles were published between 1969 and 2014 and belonged to 14 journal sources. There were 43 original articles and seven review articles. The mean duration from the date of publication was 22.6 years per article. The average citations per paper were 417.4 and the average citations per article per year were 22.6. There were 187 authors with 205 appearances contributing to these articles. Most articles were published in the decade 2000–2009. Figure 1a shows the year-wise annual contribution to the top fifty cited articles.

Fig. 1.

a Year-wise annual contribution to the top fifty cited articles concerning meniscus; b Year-wise trend of the annual citations per article per year among the top fifty cited articles

Citation Information

The top fifty cited articles had a total of 21,294 citations. Table 2 provides the citation details of each of the fifty articles included in the list. The top 10 articles with the most citations per year, i.e. average annual citations, are listed in Table 3. Figure 1b shows the year-wise trend of the annual citations per article per year. The decade 1990–1999 had the most citations per article.

Table 3.

Top 10 articles with the highest average annual citations

S. no	Article	Year	Journal	Citations per year
1	The long-term consequence of anterior cruciate ligament and meniscus injuries – osteoarthritis [7]	2007	AM J SPORT MED	83.00
2	Knee injury and osteoarthritis outcome score (KOOS)—Development of a self-administered outcome measure [6]	1998	J ORTHOP SPORT PHYS	75.43
3	Whole-organ magnetic resonance imaging score (WORMS) of the knee in osteoarthritis [9]	2004	OSTEOARTHR CARTILAGE	49.00
4	Incidence and Trends of Anterior Cruciate Ligament Reconstruction in the United States [32]	1984	AM J SPORT MED	47.00
5	A retrospective case–control injuries analysis of 2002 running [10]	2002	BRIT J SPORT MED	43.74
6	Knee osteoarthritis after anterior cruciate ligament injury a systematic review [17]	2009	AM J SPORT MED	38.00
7	Autologous Chondrocyte Implantation A Long-term Follow-up [20]	1998	AM J SPORT MED	37.55
8	Evolution of semi-quantitative whole joint assessment of knee OA: MOAKS (MRI Osteoarthritis Knee Score) [31]	2011	OSTEOARTHR CARTILAGE	33.80
9	Increase in Outpatient Knee Arthroscopy in the United States: A Comparison of National Surveys of Ambulatory Surgery, 1996 and 2006 [34]	2011	J BONE JOINT SURG AM	32.10
10	Cartilage injuries: A review of 31,516 knee arthroscopies [11]	1997	ARTHROSCOPY	32.04

AM J SPORT MED—American Journal of Sports Medicine; ARTHROSCOPY—Arthroscopy: The Journal of Arthroscopic and Related Surgery; BRIT J SPORT MED—British Journal of Sports Medicine; J BONE JOINT SURG AM—The Journal of Bone and Joint Surgery. American Volume; J ORTHOP SPORT PHYS—Journal of Orthopaedic & Sports Physical Therapy; OSTEOARTHR CARTILAGE—Osteoarthritis and Cartilage

Sources

The major contribution (50%) of the articles comes from two sources, “Journal Of Bone And Joint Surgery-American Volume (JBJS)” and “American Journal Of Sports Medicine (AJSM)”. Figure 2a shows the distribution of the top fifty cited articles among different source journals.

Fig. 2.

a Distribution of the top fifty cited articles among different journal sources; b Global contribution to the top fifty cited articles

Countries

The articles from the United States contributed to the maximum citations followed by Sweden. However, average citations per paper were higher for the articles from Sweden. Figure 2b shows the global contribution to the top fifty cited articles.

Affiliations

Over half of the top-cited articles were contributed by four institutions, the University of Pittsburgh (US), Hospital for Special Surgery New York (US), Boston University (US) and Lund University (Sweden).

Nature of Published Articles and Level of Evidence

There were 24 clinical studies, 12 cadaveric studies, two radiological basic science studies, five score evaluation-based studies, and seven review articles (Table 4). Among the clinical studies, three had level I, twelve had level II, three had level III, and six had level IV of clinical evidence. Two studies were related to radiological scoring, and three were related to clinical scoring.

Table 4.

Subtypes of clinical studies included in top fifty cited articles related to meniscus

Clinical (n = 24)	Basic science and experimental studies (n = 14)	Classification and scoring system (n = 5)	Review (n = 7)
Therapeutic—9 (6 prospective, 3 retrospective)	Cadaveric-12 (9 Biomechanical experimental studies, 3 basic science)	Radiological scoring—2	Two basic science review ( both narrative reviews)
Prognostic—13 (3 prospective, 4 epidemiological, 6 retrospective)		Clinical scoring—3
Diagnostic—3 (2 prospective, 1 retrospective)			Five clinical ( 4 narrative, 1 systematic review)
Level of evidence I: 3	Radiological-2 (basic science)
Level of evidence II: 12
Level of evidence III: 3
Level of evidence IV: 6

Discussion

General Information

There has been a surge in the available evidence concerning meniscus and its disorders, most likely linked with the prevalence of meniscal injuries among young active and elderly patients and the changing treatment perspective for these injuries. When it is well known that meniscus plays a vital role in knee joint stability and weight transmission, there has been a focus on meniscus preservation, contrary to the previously advocated excision procedures. It may be difficult to identify the researchers’ significant evidence and interest areas with vast ever-evolving literature about the meniscus. A bibliometric analysis of top-cited articles reflects the trends and interests of orthopaedic surgeons globally. Such an analysis can help understand the well-established evidence, the topics that are gaining interest, and the topics that require further research due to limited evidence. Furthermore, it could be an educational tool to familiarise orthopaedic residents and students interested in orthopaedic surgery with the “classic” publications in meniscus research. The current bibliometric analysis focuses on the meniscus and its disorders. With over 8000 orthopaedic relevant publications related to the meniscus in 64 years (1956–2020), the volume of evidence concerning the meniscus is vast.

With the years 1969–2014 contributing to the list of top fifty cited articles on the meniscus, the number of papers belonging to recent years is high. The last decade (2000–2009) alone contributed to the twenty articles on the list. The top fifty cited articles contributed to 20,887 citations, suggesting extensive research in the meniscus field. As far as the citations per paper are concerned, the decade 1990–1999 was the most productive decade with a mean of 507.61 citations per article. However, the citations’ annual rate, i.e., citations per paper per year, was high for recent years. Six out of the top ten articles with the highest annual citation rate were published from 2000 onwards. This trend suggests the high impact contributions related to the meniscus in recent years. Most of the articles are contributed by two major journals, the AJSM (13 articles) and JBJS Am (12 articles). These contributions correlate with the high impact factor of these journals and researchers’ trust in them. Looking at the global contribution to meniscus-related research, more than half comes from the United States and Sweden. Except for Japan and Australia, all the listed articles originated from western counties. The United States leads in total article citations and scientific contributions to the top fifty cited articles. However, Sweden is on the top in average citations per paper, suggesting more impactful scientific contributions. The University of Pittsburgh in the United States and Lund University in Sweden were the highest contributing affiliations in their respective counties.

Trending Topics in Research

The subjects of interest and the top-cited articles’ highlighted topics provide a basic idea of how the knowledge has gradually evolved over the years. We classified the research into clinical studies, basic science and experimental studies, clinical and radiological scores related studies, and review articles. There were twenty-four clinical studies (three level-I studies, twelve level-II, three level-III, six level-IV) (Table 4). As most of the cited clinical articles belong to prospective data (level-I and-II studies), the citation volume reflects an overall superior clinical level of evidence. The studies evaluating clinical scores were separately considered.

Clinical Studies

Twenty out of twenty-four clinical studies were published from 1990 onwards, which could be linked with the development of interest in the meniscus in the later years and subsequent generation of clinical evidence. Eight out of 24 studies studied the association of meniscus injuries with other concomitant knee injuries and long-term outcomes. Curl et al. [11], Hjelle et al. [13], and Widuchowski et al. [30] observed that meniscus injuries, especially the medial meniscus were quite prevalent concomitant injuries with chondral lesions (Approximately 40%). Thus, a high index of suspicion for meniscus tears should be observed while handling chondral lesions, and they should be preserved whenever possible. Roos et al. [28], Allen et al. [33], Bhattacharyya et al. [43], Gale et al. [46], and Oiestad et al. [48] observed the association of meniscus injuries, meniscectomy and meniscal subluxation alone, or ACL (Anterior cruciate ligament) injuries with late-onset knee osteoarthritis. The incidence was higher in patients with concomitant ACL injuries. However, not all meniscal tears contribute to symptomatic osteoarthritis of the knee, and no correlation between painful knee osteoarthritis and meniscus tears has been established. Therefore, the magnetic resonance imaging (MRI) evidence of meniscus tears in osteoarthritic has little value. Ten studies out of 24 clinical studies focused on the clinical outcomes and management following meniscus injuries. Five studies focused on outcomes other than osteoarthritis following meniscectomy [16, 19, 20, 49, 51]. Tapper et al. [16] advocated for peripheral rim preservation during meniscectomy. Only 40% of patients that underwent meniscectomy were found to have near-normal knee functions. Johnson et al. [19] found that the prolonged symptoms due to meniscal injury correlate with less clinical improvement following meniscectomy. Peterson et al. [20] observed that unipolar meniscus lesions had a better prognosis. Aglietti et al. [51] found a significant correlation between medial meniscectomy and persistent pivot shift in patients after ACL reconstruction. Shelbourne et al. [49] observed that although the patients with the intact meniscus in ACL surgery had better KT1000 scores, more than half of the patients undergoing single or both menisci removal had near-normal IKDC scores. Daniel et al. [8], Muneta et al. [37], and Salmon et al. [36] observed that meniscus’s status could not predict the ACLR (ACL reconstruction) surgery’s outcome. Daniel et al. [8] found a higher incidence of joint degeneration in patients undergoing ACLR without the need for meniscal surgery, suggesting that outcomes may not always correlate to meniscus status. Muneta et al. [37] and Salmon et al. [36] observed that meniscus repair or intact status could not predict the risk of future graft rupture. Among the remaining two studies, Cannon et al. [42] observed better healing of meniscal injuries associated with ACL reconstruction compared to the isolated meniscus tears. The hematoma probably helps in the healing process of the meniscus. Milachowski et al. [38], in their unique case series, observed high patient satisfaction with homologous meniscal transplantation.

Five of the 24 clinical studies were epidemiological studies, which suggested meniscus injuries to be the most common sports injuries among adults and the most common indication for arthroscopic evaluation [10, 29, 32, 34, 35]. In athletes, however, ACL injury was more common. One study estimated the accuracy of MRI in diagnosing meniscus tears based on arthroscopic evaluation [44]. The accuracy was estimated to be 88–89%.

Radiological and Functional Assessment Scores

Five of the listed studies were related to radiological and functional outcome scores. Roos et al. [6] formulated and evaluated KOOS (Knee injury and osteoarthritis outcome score) that incorporated WOMAC (Western Ontario and McMaster Universities Osteoarthritis Index) score as well. The reliability, responsiveness and validity were high. The questionnaire was patient self-administered and took an average of 10 min. The assessment was made under five groups: pain, symptoms, knee function, daily living activities, and knee-related quality of life. Interestingly, this article was the most cited article, along with the second-highest annual citation rate (per year). The high citation ranking signifies the wide and continued acceptance of this score. Peterfy et al. [9] evaluated an MRI scoring method (WORMS) that incorporated 14 features: articular cartilage integrity, subarticular bone marrow abnormality, subarticular cysts, subarticular bone attrition, marginal osteophytes, medial and lateral meniscal integrity, anterior and posterior cruciate ligament integrity, medial and lateral collateral ligament integrity, synovitis/effusion, intraarticular loose bodies, and periarticular cysts/bursitis using conventional MR images, and showed high inter-observer agreement among trained readers. This study also had a high overall citation rank of 4th and third-highest citation rate per year. In 1998, Roos et al. [25] validated the Swedish version of KOOS. Hunter et al. [31] analysed the effectiveness of an MRI-based knee osteoarthritic score based on location and characteristics of bone marrow lesions, cartilage lesions and meniscal morphology (adding meniscal hypertrophy, partial maceration, and progressive partial maceration). The score was found to be highly reliable. Although listed at 26th order in the total citation order, the study was listed at the 8th position in the annual citation rate since publication. Irrgang et al. [22] attempted to formulate an outcome score based on patient-reported outcomes. The score reflected problems reported by patients who had ligamentous or meniscal injuries, patellofemoral pain, or osteoarthrosis. The symptoms included in their scale (termed as Activities of Daily Living Scale) were pain, crepitus, stiffness, swelling, instability, and weakness. Results suggested that the Activities of Daily Living Scale was a reliable, valid, and responsive instrument for assessing functional limitations that result from a wide variety of pathological disorders and impairments of the knee. Overall, it can be stated that diagnostic and outcome scores continue to be essential tools based on citation volume and rates.

Cadaveric and Basic Science Studies

Twelve of the listed studies were cadaveric ones. These articles were published between 1976 and 2008. Six studies concluded the role of menisci in load transmission, and reduction in effective stress on articular surfaces [14, 23, 24, 26, 41, 45]. Additionally, Allaire et al. [24] and Lee et al. [45] concluded that segmental meniscectomy and root tears were equivalent to total meniscectomy. Root repair was able to re-establish the normal load transmission role of the meniscus. Three studies found the augmentary role of the meniscus in anteroposterior stability [15, 39, 52]. Combined ACL and medial meniscal tears were found to have the highest anterior translation of tibia, while isolated meniscal tears did not compromise the knee stability. Three cadaveric studies were related to basic science. They dealt with the vascularity of the meniscus, highlighting its peripheral vascular zone [12], the development and microarchitecture of the meniscus [55], and the location of the tunnel of the anatomic anterior cruciate ligament reconstruction concerning the anterior horns of the meniscus [53].

Two listed articles were related to the radiological evaluation of the knee. Potter et al. [21] observed that a specialised fast-spin-echo magnetic resonance imaging sequence with a high-resolution matrix allows for an accurate assessment of articular cartilage in the knee with little inter-observer variability. Even in the absence of substantial intra-articular joint fluid, this pulse sequence permitted differentiation among articular cartilage, subchondral bone, and meniscus. Peterfy et al. [27] designed an OA (Osteoarthritis) MRI protocol to accurately delineate the articular structures of the knee, including the menisci. External validation was, however, not performed.

Review Articles

There were seven review articles in the current analysis. Lohmander et al. [7] provided a comprehensive review suggesting the risk of meniscus tear and meniscus surgery in ACL deficient knee joints. Although meniscus tears have been associated with OA’s risk, additional features of primary OA further increase knee OA risk. This review stood 2nd in the list of top citations and first in the annual citation rate list. The top citation order signifies the currently ongoing research on ACL and meniscus injuries’ long-term outcomes. Øiestad et al. [17] and Gillquist et al. [47] published their reviews on the same topic, i.e., long-term results following ACLR with special attention on knee OA. The review by Øiestad et al. [17] was a systematic review. This review paper was a landmark paper. There had been preceding focal reports of higher incidence of OA in patients undergoing ACLR compared to those managed without surgery. However, the review suggested a low prevalence of knee osteoarthritis for individuals with isolated anterior cruciate ligament injury (0–13%) and a higher prevalence for subjects with combined injuries, especially with meniscal injuries (21–48%). Thus, the higher incidence of OA following ACLR was a mere non-causal association, probably related to greater joint damage due to injury. As suggested by the sixth rank in the annual citation rate, this systematic review has further gained importance. McDermott et al. [40] highlighted the impact of meniscectomy on intra-articular contact stresses, radiological evidence of joint degeneration, and risk of joint malalignment with meniscectomy with low valgus or varus knees. Also, the importance of meniscus preservation was highlighted. Three review articles were related to the basic science of meniscus, i.e., material properties, structure and functional relationship of menisci [18], ultrastructure and biochemistry of meniscal cartilage [50], and effect of PDGF and IGF on cartilage healing [54].

Ongoing Interests

Considering the long time frame of articles inclusion, the current analysis cannot predict the most relevant topics of current interest in the meniscus and related conditions. However, it can provide an idea of topics that are still relevant or have an ongoing interest. As discussed above, the clinical outcome scores are still trending topics. Besides this, there is continued interest in the long-term outcomes of ACL reconstruction and meniscus injuries, particularly concerning long-term osteoarthritis. The epidemiological studies continue to form the basis of research formulation. As there is increasing evidence supporting meniscus preservation, a similar trend can be observed in preserving cartilage by autologous chondrocyte implantation. Two of the top 10 annually cited articles belong to MRI-based evaluation of the knee, suggesting the increasing role and advancement in MRI based on the assessment of the knee and its disorders.

Missing Topics

Although the current analysis covers a broad spectrum of meniscus linked issues, some critical meniscus-related topics were either missed or only slightly touched in the top fifty cited articles. We observed that papers related to meniscus repair methods, the open and closed meniscus procedures, meniscus reconstruction and special meniscal lesions were greatly missing from the top citation list. Only one cited study had discussed the effectiveness of homologous meniscus transplantation. Recent interest in the meniscus reconstruction could be the reason for these critical topics found missing in the citation list. Moreover, the top annually cited articles that potentially represent the continued topics of interest could not highlight these advances in meniscus research. The interest in concurrent issues probably outweighed the advancements in meniscus research. As discussed prior, anterior cruciate ligament and knee osteoarthritis are trending contemporary topics with the meniscus. The first major study with long-term results of meniscus repair was performed by DeHaven et al. [56] in 1989. The study has 134 citations (on the Web of Science database) and could not qualify for the top fifty citation list. Another significant lacuna detected in the current analysis is the lack of publications from Asian and African countries. A variety of factors, including the limitations of resources, could have played a role in these developing regions.

Limitations of the Current Analysis

Various medical specialities have considered bibliometric analysis a useful tool to measure the most impactful scientific production in a specific field. However, like other such studies, the current research has several limitations. First, the current analysis is based on a single primary scientific database. Although the database caters to many high impact journals and indices, it is not an all-inclusive database and is bound to restrict the current analysis. Second, the current study is restricted to English, which means that articles published in other languages would have been missed. Third, citation analysis does not account for author self-citation, which might falsely inflate an article’s value. Fourth, although we had included the annual citation rate to decrease bias toward earlier publications, our primary ranking method was “total citation” analysis. Fifth, the articles with numerous citations and those published in more influential journals have more chances of further citation. The current analysis cannot control that bias. Sixth, the current analysis cannot predict the recent citation trends, which would probably need an analysis of the recent highly cited articles. Lastly, the research published in non-orthopaedic, non-sports sciences and non-surgical journals were not included in the current analysis and could have potentially influenced the results.

Conclusion

The meniscus is an emerging topic of interest in the field of orthopaedics and sports medicine. The recent evidence highlights the importance of meniscus preservation, the link between meniscus injuries and concomitant anterior cruciate ligament and chondral injuries, its role in long-term gonarthrosis. In addition, the meniscus repair and transplantation techniques have recently gained importance and will need further research to qualify for the top-cited evidence.

Author Contributions

AZA, AK contributed with concept, design, data analysis, manuscript preparation, manuscript editing, and manuscript review. KMAJ, AMS, AK contributed with manuscript preparation, and manuscript editing. SS, AK contributed with data acquisition, data analysis, manuscript preparation, manuscript editing, and manuscript review. RK, AA contributed data acquisition, data analysis. SM contributed in literature review, manuscript editing, and manuscript review.

Funding

This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors.

Availability of Data and Material

Data assessed can be provided on request.

Code Availability

Not applicable.

Declarations

Conflict of Interest

None of the authors has any conflicts or competing to declare.

Ethics Approval

Not applicable (No human or animal subjects).

Consent to Participate

Not applicable (No human or animal subjects).

Consent to Publish

Not applicable (No human or animal subjects).