WHAT IS ALREADY KNOWN ON THIS TOPIC

Arthroscopic partial meniscectomy (APM) provides no additional benefit for pain and knee function compared with exercise therapy; however, the long-term consequences of treatment choice on knee osteoarthritis (OA) progression in middle-aged individuals with degenerative meniscal tears and minimal concomitant knee OA remains uncertain.

WHAT THIS STUDY ADDS

Ten years following APM or exercise therapy for degenerative meniscal tears, there were no essential between-group differences in radiographic knee OA progression.

Both treatments were associated with substantial improvements in patient-reported outcomes that were sustained over the 10-year follow-up period.

HOW THIS STUDY MIGHT AFFECT RESEARCH, PRACTICE OR POLICY

Exercise therapy should be the preferred treatment over APM for middle-aged individuals with degenerative meniscal tears.

Our findings substantiate previous evidence suggesting no additional benefit of APM compared with exercise therapy as treatment for degenerative meniscal tears on structural and clinical outcomes.

Introduction

Degenerative meniscal tears are found in every fourth knee of middle-aged individuals in the general population, and incidental tears in asymptomatic individuals are prevalent.1 The choice of treatment for those with a confirmed degenerative meniscal tear and knee symptoms has been contentious.2 Traditionally, arthroscopic partial meniscectomy (APM) has been the treatment of choice, but several high-quality randomised controlled trials have demonstrated no clinically relevant benefits over exercise therapy or sham surgery in patient-reported outcomes during follow-ups of 2–5 years.3–12 Furthermore, individual participant data meta-analysis from four randomised trials failed to identify subgroups of patients with additional benefits from APM (eg, patients with mechanical symptoms).13

Degenerative meniscal tears and meniscal resection are risk factors for knee osteoarthritis (OA).14 15 The long-term consequences of treatment choice, particularly in middle-aged individuals with no or minimal concomitant knee OA, remain a subject of ongoing debate.16 17 In those with moderate to severe OA, surgically treated patients show higher rates of radiographic knee OA deterioration compared with those treated with exercise over 5 years.10 Greater OA progression based on MRI features following APM and increased risk of knee replacement surgery compared with exercise therapy have also been reported.8 18 The Odense-Oslo Meniscectomy versus Exercise (OMEX) trial is the only long-term follow-up study including individuals with minimal radiographic OA changes.3 At 5-year follow-up, no relevant between-group differences were observed in radiographic knee OA progression.4

The primary aim of this 10-year follow-up study of the OMEX trial was to compare progression of radiographic knee OA following APM and exercise therapy in patients with a degenerative meniscal tear and minimal concomitant knee OA. Secondary aims were to compare knee OA development and changes in patient-reported outcomes and knee muscle strength.

MethodsStudy design

We conducted a 10-year follow-up assessment of patients included in the OMEX trial, a randomised controlled trial comparing APM with exercise therapy. The recruitment phase spanned from October 2009 through September 2012. The patients were randomised in a 1:1 ratio using a computer-generated randomisation sequence, stratified by sex in blocks of eight. An independent statistician determined the randomisation scheme and concealed the allocations in sequentially numbered opaque envelopes. We reported the study in line with the Consolidated Standards of Reporting Trials guideline and the Template for Intervention Description and Replication guideline.19 20

Deviations from trial registration

In the original trial registration, the primary outcome at 5 years was described as incident and enlarging marginal tibiofemoral osteophytes. However, since the prespecified aim was to describe radiographic changes in knee osteoarthritis development, the primary outcome was changed to the Osteoarthritis Research Society International (OARSI) atlas assessing both osteophytes and joint space narrowing.21 The same primary outcome measure was used in this 10-year follow-up study, which was registered (NCT01002794) prior to the 10-year data collection.

Participants

We enrolled patients aged 35–60 years with non-traumatic unilateral knee pain lasting over 2 months, confirmed by MRI to have a medial degenerative meniscal tear, and Kellgren and Lawrence (K&L) grade 2 at most. All patients were considered eligible for surgery by one of two experienced orthopaedic surgeons based on patient history and clinical examination, in addition to the meniscal tear defined as an intrameniscal linear MRI signal penetrating one or both surfaces of the meniscus. Recruitment took place at two orthopaedic departments in Norway: Oslo University Hospital (October 2009 through April 2011) and Martina Hansens Hospital (May 2011 through September 2012).

Interventions

The arthroscopic evaluation and resection of the meniscus were performed at the hospital of recruitment. The procedure involved inspection of the knee joint for the presence of intraarticular pathology, systematic probing of both menisci and subsequently resection of all unstable meniscal tissue. All patients received written and oral postoperative instructions, including simple home exercises. The arthroscopic procedure and postoperative routines have been described in detail elsewhere.3

The 12-week exercise therapy intervention took place at one of two participating physiotherapy clinics. Both clinics followed the same standardised treatment protocol, consisting of progressive neuromuscular and strengthening exercises. The treatment programme was performed 2 to 3 times per week, with 1 weekly session supervised by a physical therapist.22

Data collection

Baseline data were collected before randomisation, involving standardised weight-bearing radiographs obtained at the recruiting hospital, patient-reported questionnaires and isokinetic muscle strength testing. Subsequent radiographic assessments at a private radiographic clinic at 5 and 10 years used the same standardised protocol. The protocol specified posterior-anterior radiographs without fluoroscopic guidance, 10° caudal X-ray beam angulation and the use of a Synaflexer (Synarc) positioning frame.23 Patient-reported questionnaires and isokinetic muscle strength testing were completed during clinic visits at follow-ups after 3 months, 12 months, 24 months (questionaries only), 5 years and 10 years. The 10-year follow-up assessments were conducted from June 2020 through October 2022.

Primary outcome

The primary outcome was the change from baseline in the OARSI atlas sum score at 10 years. The OARSI atlas assesses tibiofemoral osteophytes and joint space narrowing separately in the medial and lateral compartments, graded from 0 to 3 (normal to severe OA changes).21 Half grades were used if progression had occurred without achieving a full grade.24 Participants with subsequent tibial osteotomy were assigned a joint space narrowing score of 3 for the affected compartment, and those who received total knee replacement were scored as 3 for both joint space narrowing and osteophytes. Based on the individual radiographic features, a sum score was calculated, representing the sum of medial and lateral compartment joint space narrowing and osteophyte score (continues outcome, range 0–18). Two experienced radiographic readers (LE and CNE), blinded to group allocation, graded all radiographs independently, with any disagreements resolved in a consensus session. All available radiographs for each participant were processed together, with known time sequence.

Secondary outcome

Knee OA incidence based on the K&L classification was included as secondary radiographic outcome. The K&L classification grades knee OA severity from 0 (normal) to 4 (severe),25 26 and we defined incidence as the emergence of grade ≥2 at 10 years in knees graded 0 or 1 at baseline (dichotomous outcome: yes or no). Participants with incident radiographic knee OA experiencing knee pain at least weekly were classified as having symptomatic knee OA.

Other secondary outcomes were changes from baseline in the five subscales of the Knee injury and Osteoarthritis Outcome Score (KOOS): pain, other symptoms, activities of daily living (ADL), sport and recreational function (sport/rec) and knee-related quality of life (QoL).27 Additionally, we compared changes in KOOS4, a composite score calculated as the mean of all subscale scores except for ADL.

Finally, we compared changes from baseline in quadriceps and hamstrings muscle strength assessed using an isokinetic dynamometer (Biodex 6000). Concentric knee extension and flexion were tested at 60°/s from 90° to full extension. Peak torque (Nm) normalised for body weight (Nm/kg) was used in the data analysis. The same dynamometer and a detailed test protocol were used by trained assessors at baseline and follow-ups.28 Baseline chair settings were recorded to ensure consistent participant positioning, with necessary adjustments made to align the anatomical axis of rotation to the dynamometer axis.

Patient and public involvement

No patients were involved in the planning or conduct of this 10-year follow-up study, but patients and clinicians were involved in the development and implementation of the exercise therapy programme. User experiences and results from the OMEX trial are disseminated to clinicians and patients through a nationally implemented osteoarthritis treatment programme (AktivA).29

Equity, diversity and inclusion statement

The author team consists of men and women from various health disciplines, career stages and countries. Patients from two public hospitals in different regions of Oslo, Norway, were included, contributing to increased socioeconomic diversity.

Statistical analyses

The primary analyses were performed with all participants analysed as randomised, irrespective of treatment received or crossover. Continuous outcomes (OARSI sum score, KOOS and knee muscle strength) were analysed using intention-to-treat linear mixed models, fitting all available data. For the OARSI sum score, we included participant as random effect with random intercept, with fixed effects factors for time point (baseline, 5 years and 10 years), time×treatment interaction and the randomisation stratification factor (sex). We adjusted for baseline value of the outcome by not including a main effect for treatment.30 Secondary continuous outcomes (KOOS and knee muscle strength) were analysed using the same approach. Results are presented as means with 95% CIs.

For binary outcomes (radiographic and symptomatic knee OA incidence), the analyses were performed on the full-analysis set,31 excluding participants with missing data. Between-group differences were analysed using Poisson regression with robust SEs,32 with separate models for radiographic and symptomatic knee OA. Both models were adjusted for the randomisation stratification variable. Participants with K&L grade 2 at baseline were not included in analyses of OA incidence. We present the results as adjusted risk differences with 95% CI. Relative effect sizes are also reported.19

Sensitivity analyses were conducted to assess the impact of non-ignorable missingness. For OARSI sum score and patient-reported outcomes, the baseline observation was carried forward, representing best-case and worst-case scenario approaches, respectively. For binary outcomes (OA incidence), we used last observation carried forward. An as-treated analysis was also performed to estimate the effect of receiving treatment. In the as-treated analyses, the APM group included patients who crossed over from the exercise group, whereas patients not receiving their allocated treatment were excluded. All analyses were performed using Stata V.18.0 (StataCorp, College Station, Texas, USA).

Results

Of the 341 screened patients, 140 were randomised: 70 to APM and 70 to exercise therapy (figure 1). At the 10-year follow-up, 31 participants (22.1%) did not attend the radiographic assessment (11 (15.7%) APM and 20 (28.6%) exercise). In the APM group, 11 participants (15.7%) did not return questionnaires and 14 (20.0%) did not attend muscle strength testing. In the exercise group, 18 participants (25.7%) did not return questionnaires or attend muscle strength testing. A flow diagram including all follow-ups is found in online supplemental figure 1. The baseline characteristics of the two groups were balanced for sex, age, body mass index and radiographic OA severity (OARSI sum score and K&L) (table 1). The APM group reported shorter symptom duration and had somewhat better KOOS scores and higher knee muscle strength (table 1). Baseline characteristics were comparable between participants lost to follow-up and those who contributed 10-year data (online supplemental table 1).

Table 1

Baseline characteristics of the OMEX participants

Figure 1

Flow diagram of participants in the study for the primary outcome.

Of the participants allocated to exercise, 14 (20%) crossed over to receive APM (4 of whom declined exercise therapy) before the 2-year follow-up. No participants in the APM group crossed over to exercise therapy.3 Before the 5-year follow-up, five participants in the APM group had subsequent surgeries (APM n=3, osteotomy n=1, total knee replacement n=1) 4–36 months after the index procedure. In the exercise group, two participants who had crossed over to APM had subsequent surgeries 6 months after the initial procedure (reoperation or osteotomy).4 No new operations were reported between the 5-year and 10-year follow-ups.

The OARSI sum score at 10 years was 2.82 (95% CI 2.39 to 3.25) in the APM group and 2.43 (95% CI 1.97 to 2.89) in the exercise group. The adjusted mean difference in change was 0.39 (95% CI −0.19 to 0.97) (table 2). The incidence of radiographic knee OA was 23% (13 of 57) in the APM group and 20% (10 of 49) in the exercise group. The adjusted risk difference was 3% (95% CI −13% to 19%). The distribution of K&L grades at 10 years is presented in online supplemental table 2. Symptomatic knee OA incidence was 14% (8 of 56) in the APM group and 10% (5 of 48) in the exercise group (adjusted risk difference 4% (95% CI −9% to 17%)). Relative effect sizes are presented in online supplemental table 3. In the APM group, 66% (37 of 56) did not report knee pain and had not developed radiographic knee OA at 10 years (figure 2). The corresponding number in the exercise group was 65% (31 of 48).

Table 2

Change from baseline to 10 years in OARSI sum score, patient-reported outcomes and knee muscle strength

Figure 2

Area-proportional Venn diagram showing proportions of participants with knee pain during the last week, incident radiographic osteoarthritis (OA) and no pain or incident radiographic OA in the (A) arthroscopic partial meniscectomy (APM) group and (B) exercise group. Intersection represents participants with symptomatic knee OA.

Both groups reported substantial improvements in patient-reported outcomes over the 10-year follow-up period, with changes predominantly occurring within the first 2 years (figure 3). No clinically relevant between-group differences were observed in KOOS4 or any of the individual KOOS subscales (table 2). The adjusted between-group difference in KOOS4 was −2.4 points (95% CI −7.6 to 2.8) in favour of the exercise group. The 10-year trajectories of the individual KOOS subscales are shown in online supplemental figure 2.

Figure 3

Mean KOOS4 scores for both treatment groups over the 10-year follow-up. Based on linear mixed models with adjustment for baseline value of the outcome and sex. Error bars indicate 95% CI. APM, arthroscopic partial meniscectomy; KOOS, Knee injury and Osteoarthritis Outcome Score.

We found no statistically significant between-group difference for change in isokinetic quadriceps strength (table 2). For isokinetic hamstrings strength, we found a statistically significant between-group difference in favour of the exercise group (adjusted mean difference −0.07 Nm/kg (95% CI −0.13 to −0.01)). There was no change from baseline to 10 years for isokinetic quadriceps strength in the two groups, while isokinetic hamstrings strength declined slightly in the APM group (table 2). The 10-year trajectory of quadriceps and hamstrings muscle strength is shown in figure 4.

Figure 4

Mean isokinetic quadriceps and hamstrings strength for both treatment groups over the 10-year follow-up. Based on linear mixed models with adjustment for baseline value of the outcome and sex. Error bars indicate 95% CI. APM, arthroscopic partial meniscectomy.

No serious adverse events related to the interventions were recorded at the 2-year follow-up.3

The sensitivity analyses for OARSI sum score progression and changes in KOOS subscale scores confirmed the robustness of the primary analyses (online supplemental table 4). In the sensitivity analysis for OA incidence using last observation carried forward, 21% (14 of 67) in the APM group and 16% (11 of 69) in the exercise group developed radiographic knee OA over 10 years (adjusted risk difference 5% (95% CI −8% to 18%)). For symptomatic knee OA, the incidence was 12% (8 of 67) in the APM group and 7% (5 of 69) in the exercise group (adjusted risk difference 5% (95% CI 5% to 15%)). The as-treated analysis included 78 participants in the APM group and 50 participants in the exercise group. In the OARSI sum score, the adjusted between-group difference in change from baseline to 10 years was 0.57 (95% CI −0.05 to 1.20), with more progression in participants undergoing APM. Consistent results with the primary analysis were found for changes in patient-reported outcomes and knee muscle strength (online supplemental figure 3). Among participants with 10-year radiographic data, 25% (16 of 63) of participants treated with APM and 18% (7 of 38) of those participating in exercise therapy developed radiographic knee OA (adjusted risk difference 9% (95% CI −8% to 25%)). For symptomatic OA, the numbers were 16% (10 of 62) in the APM group and 8% (3 of 37) in the exercise group (adjusted risk difference 9% (95% CI −4% to 21%)).

Discussion

Ten years following APM or exercise therapy for degenerative meniscal tears, we found no essential between-group difference in progression of radiographic knee OA and comparable rates of knee OA development. The OMEX trial participants, who had no or minimal concomitant knee OA at inclusion, experienced substantial improvements in patient-reported pain and knee function on average, with no clinically relevant differences between the two treatment groups. These findings extend current knowledge regarding the long-term consequences of treatment choice in individuals with degenerative meniscal tears and minimal concomitant OA, substantiating previous evidence suggesting no clinically relevant difference between APM and exercise therapy.

Observational studies have previously indicated a detrimental effect of meniscal resection on knee cartilage and subsequent radiographic progression.15 33 Disentangling whether the increased risk is directly attributable to the surgical procedure or the underlying meniscal tear is challenging due to the observational nature of these studies.34 In our primary outcome, the OARSI sum score, we found a mean difference in change of 0.39 (95% CI −0.19 to 0.97), with more progression in the APM group. While cross-sectional data suggest a strong relationship between individual radiographic features and knee pain,35 the influence on downstream pain and function is unclear, such as the clinical relevance of a 1 OARSI grade difference. Considering the width of the CI, we believe a relevant difference in favour of APM can be excluded (lower bound −0.19) and that a relevant difference in favour of exercise can also most likely be excluded (upper bound 0.97). However, other trial data indicate a relationship between APM and structural deterioration. In the MeTeOR (Meniscal Tear in Osteoarthritis Research) trial, surgically treated patients showed greater advancement in MRI-based cartilage, osteophyte and effusion-synovitis score over 18 months compared with the exercise group,18 while Sonesson et al reported radiographic deterioration in 60% of surgically treated patients compared with 37% of patients treated with exercise at 5 years.10 These studies included 55% and 40% of participants with KL grade ≥2 at baseline, respectively, compared with only 3% of our OMEX trial participants. The difference in baseline OA status may explain the differences to our 10-year follow-up results.

The findings of no clinically relevant between-group differences in patient-reported outcomes are consistent with the results of other trials at shorter follow-ups (2–5 years).5–10 The absolute 10-year KOOS subscale scores of our OMEX participants indicate minimal limitations in pain, other symptoms and ADL, which were on par with age-specific reference data.36 Impairments were somewhat more apparent for function in sport and recreational activities and knee-related quality of life, likely attributable to established degenerative changes in this early knee OA population. However, this may also reflect relatively high functional requirements of the physically active participants included in our trial.37 This is also evident in the observed 10-year trajectory of knee muscle strength, with quadriceps and hamstrings strength being similar to baseline levels. Although we found exercise therapy effective in improving muscle strength up to 12 months compared with APM,28 this difference was attenuated over time, and between-group differences at 10 years were minimal.

Clinical and research implications

The 10-year follow-up results of the OMEX trial corroborate clinical practice recommendations that advise against performing APM in individuals with degenerative meniscal tears.38 However, research is needed to elucidate the clinical implications of structural changes on future patient-relevant outcomes in individuals with degenerative meniscal tears and early OA. Currently, the clinical meaning of radiographic changes remains uncertain, as reflected in the similar proportions of participants with and without radiographic knee OA who reported knee pain (see figure 2).

Limitations

The OMEX trial’s strengths and limitations have been discussed previously.3 4 An overall strength is the multiple assessment with a high retention rate across previous follow-ups (≥86%). Although 78% attended the 10-year follow-up for the primary end point, a limitation is the somewhat unbalanced comparative loss rates in the randomised groups. Twenty participants (28.6%) in the exercise group were lost compared with 11 (15.7%) in the APM group. However, these participants were similar to those included in the analysis and the mixed model analysis addresses missing data using maximum likelihood estimation. While analysis of covariance was used for the 5-year follow-up, we chose linear mixed models at 10 years due to the higher rate of missing data. Adjustment for baseline differences by omitting the main effect of treatment ensured that participants with only baseline data were included in the analysis. The estimates for between-group differences at 10 years were comparable to the results at 5 years, which, in addition to a lower rate of missing data, also had balanced comparative loss rates in the randomised groups.4 For binary outcomes, analyses were performed based on the full-analysis set, which carries a risk of bias.31 One-way cross-over is another potential limitation when comparing surgical and non-surgical treatments.39 In the OMEX trial, 14 participants (20%) crossed over to APM, which is lower than in other trials conducting long-term follow-up (between 25% and 38% at 5 years).6 8 10 It is also important to recognise that the potential impact of APM15 33 on radiographic OA progression may be underestimated when crossovers are analysed in the exercise group (to adhere to the intention-to-treat principle). The results from the as-treated analysis may suggest this, although these results should be interpreted with caution.40 Finally, the OMEX trial was designed to investigate between-group differences in patient-reported outcomes at 2 years.3 No a priori sample size calculation was performed for the 10-year follow-up; however, the inferential uncertainty, as indicated by the CIs, was sufficiently small to exclude meaningful differences for continuous outcomes. We acknowledge that we did not have sufficient power for binary outcomes, and the results for OA development are associated with uncertainty.

Conclusion

In this 10-year follow-up of individuals with degenerative meniscal tears and minimal concomitant knee OA, we found no meaningful differences in progression of radiographic knee OA and comparable rates of knee OA development following APM and exercise therapy. Both treatments resulted in substantial improvements in patient-reported pain and knee function.

Data availability statement

Data are available on reasonable request.

Ethics statementsPatient consent for publication

Not applicable.

Ethics approval

This study was approved by Regional Committee for Medical and Health Research Ethics of South-East Norway (ref-nr 2009/230). Participants gave informed consent to participate in the study before taking part.

Acknowledgments

The authors acknowledge research coordinator Kristin Bolstad for her role in the organisation of the participants and assistance with data collection; Silje Stensrud a former PhD student in the OMEX trial, physical therapist Marte Lund, Karin Rydevik, Christian Vilming and Bente Grepperud for assistance with data collection; Volvat Nimi for contributing with rehabilitation facilities and research staff and the Division of Orthopedic Surgery at Oslo University Hospital and the Department of Orthopedic Surgery at Martin Hansens Hospital for providing access to the outpatient clinics and surgical teams and facilities.