Sage Journals: Discover world-class research

Abstract

Background:

Some patients still experience mild residual rotational laxity of the knee after anterior cruciate ligament reconstruction (ACLR). The clinical symptoms of this residual rotational laxity are controversial, and methods for evaluating the symptoms have become a focus of academic interest in recent years. It is unclear whether there is a correlation between mild residual rotational laxity after ACLR and performance.

Purpose:

To investigate the influence of residual mild rotational laxity after ACLR on subjective outcomes, performance, psychological readiness, and return to sports (RTS).

Study Design:

Cross-sectional study; Level of evidence, 3.

Methods:

A total of 81 patients who underwent ACLR at our sports medicine center were observed for >2 years. The follow-up included KT-2000 measurements, the pivot shift test (PST), subjective outcome scores (Lysholm, International Knee Documentation Committee Subjective Knee [IKDC], Knee injury and Osteoarthritis Outcome Score [KOOS], ACL-Return to Sport after Injury Score [ACL-RSI], Tegner score, and Marx score), and performance evaluations, such as isokinetic testing at 60 deg/sec, hop tests, and Y-balance tests (YBT). Patients were grouped based on the results of the last PST follow-up on the operated knee. The stable group (SG) consisted of 42 patients with negative PST results, while the mild rotational laxity group (MIG) comprised 39 patients with PST grade 1. Statistical analysis was conducted to compare patient characteristics, subjective outcome scores, and performance between the 2 groups.

Results:

Significant differences were observed between the 2 groups in the single-leg hop test, the triple hop test, and the cross-over hop limb symmetry index, respectively (P = .013; P = .017; P = .046). In addition, the SG had significantly higher ACL-RSI scores than the MIG (69.54 ± 21.34 vs 53.60 ± 21.66; P = .006); and postoperative Tegner scores were significantly higher in the SG compared with the MIG (5.81±1.70 vs 4.95 ± 1.93; P = .036). No significant differences were observed in Lysholm, IKDC, KOOS score, postoperative Marx, or KT-2000 side-to-side difference scores, and no significant differences were found in isokinetic testing at 60 deg/sec, hamstring-to-quadriceps ratio, or YBT results between the 2 groups.

Conclusion:

Residual mild rotational laxity in the knee after ACLR leads to poorer performance in hop tests and a lower level of activity, and poor psychological readiness. Furthermore, in short- to medium-term follow-up after ACLR, regardless of knee rotational laxity, the return to preinjury activity rate remains low, with the majority not meeting the safe RTS criteria.

Keywords

anterior cruciate ligament psychological readiness return to sports rotational mild instability

The anterior cruciate ligament (ACL) is a significant anatomic structure in the knee that restricts anterior tibial translation and internal rotation of the tibia, commonly subject to sports-related injuries.²⁵ ACL injury leads to anterior-posterior and rotational instability of the knee, resulting in aberrant movement patterns.²⁸ Anterior cruciate ligament reconstruction (ACLR) serves as the primary intervention to restore knee stability and functionality after ACL injury, facilitating patients’ return to sports (RTS).⁸ Despite ACLR, approximately 3% to 22% of patients still experience residual mild rotational laxity in the knee postoperatively.¹³ The association between this residual instability and subjective outcome scores and performance remains uncertain, contributing to the controversy surrounding its clinical significance.^17,31 A subset of studies suggested that knee stability does not correlate with subjective outcome scores,^20,30 nor does it correlate with performance.^16,23 However, others have suggested that mild knee laxity heightens the risk of revision and significantly affects subjective outcomes.^17,24 Consequently, the evaluation of residual mild rotational laxity after ACLR has garnered substantial academic attention in recent years.

Assessment of knee rotational laxity typically involves physical examination. The pivot shift test (PST), first described by Galway and MacIntosh,⁶ is a specific assessment of rotational instability observed in ACL-injured knees and is now widely utilized in postoperative ACLR assessment. Furthermore, the patient's Lysholm score, the International Knee Documentation Committee Subjective Knee (IKDC) score, the Knee injury and Osteoarthritis Outcome Score (KOOS), the Tegner score, and the Marx score are commonly employed to evaluate the efficacy of ACLR. Among these, the Tegner score reflects the patient’s preinjury activity level and postoperative recovery, with a comparison made to ascertain whether the patient has returned to the preoperative level.²⁷ Webster et al³⁰ developed the ACL-Return to Sport after Injury Score (ACL-RSI), recognized as a reliable indicator for assessing postoperative psychological readiness.²⁶ According to the latest Panther guidelines²² of 2020, performance evaluation constitutes an integral aspect of assessing postoperative function, encompassing lower extremity muscle strength, hop tests, and Y-balance tests (YBT). Therefore, the principal aim of this study was to investigate whether residual mild rotational laxity after ACLR influences subjective outcomes and performance in short- and medium-term follow-ups. Furthermore, the study aimed to compare the disparities in subjective outcome scores and performance between patients exhibiting grade 1 and negative PST, thereby providing valuable insights for clinical treatment.

Methods

Participants

This study was conducted between November 2022 and December 2023 to observe patients who were seeking medical care at our hospital during July 2008 and December 2021 and underwent their first ACLR. Sex, age at surgery, body mass index (BMI), affected side, time from injury to surgery, meniscal injury, and follow-up time were recorded for the enrolled patients. The inclusion criteria were as follows: (1) primary single-bundle ACLR; (2) no combined posterior cruciate ligament injury; (3) the use of autologous hamstring tendon graft for ACLR; (4) ACLR performed using the anterior medial approach femoral tunnel localization technique; (5) epiphyseal closure; (6) ≥2 years of follow-up; (7) ability to be contacted and participate in the postoperative offline follow-up; and (8) no history of other surgeries affecting the knee function. The exclusion criteria were as follows: (1) ACL revision between the initial postoperative period and the follow-up period; (2) posterior cruciate ligament injury between the initial postoperative period and the follow-up period; (3) generalized ligamentous laxity; (4) other surgeries affecting the knee function between the initial postoperative date and the follow-up date; (5) a PST of ≥2 grade; (6) inability to complete all the required examinations or evaluations at the postoperative follow-up visit.

A total of 81 patients completed all required evaluations for the follow-up—including clinical examinations using the KT-2000, PST, Lysholm, IKDC, KOOS, ACL-RSI, Tegner, and Marx scores for subjective outcome scores; and the isokinetic muscle strength test at 60 deg/sec in the affected knee, hop tests, and YBTs for performance evaluations—and were included in the study (Figure 1).

Figure 1.

Flowchart of participants. ACLR, anterior cruciate ligament reconstruction; PTS, pivot shift test.

Questionnaires regarding sports participation were completed at 2 time points: preoperatively and at the postoperative follow-up. A clinical examination was performed at the last follow-up to complete the subjective outcome scores, as well as the performance tests. The study was approved by the Regional Ethics Committee (202210), and consent for the study was obtained from all included patients.

Clinical Examination

Pivot Shift Test

Each patient was examined separately by 2 specialists (J.Z. and F.G.) in the field of sports medicine. These 2 surgeons were independent examiners with no previous involvement in patient care. The absence or presence of specific criteria during flexion of the affected knee at the follow-up was classified according to the grading method proposed by Jakob et al.¹⁴ Patients with consistent grade 1 PST results were included in the mild rotational instability group (MIG), while those with grade 0 PST results were included in the stable group (SG). In cases of disagreement between examiners, the PST under anesthesia was performed. Ultimately, 5 patients were excluded from the study because they had grade 2 PST results under anesthesia.

KT-2000

We used the KT-2000 arthrometer (Medmeric) at 133 N (30 Lb) force for assessment, and the knee was flexed between 20° and 25°. The results were expressed as the side-to-side difference (SSD) between the affected side and the healthy side measurements.

Lower Extremity Muscle Strength

The patient’s peak knee extensor and flexor moments were assessed using the American Biodex system 4 isokinetic muscle strength testing system (Figure 2). This system is primarily employed to evaluate the capacity of knee flexor and extensor muscle groups to generate maximum muscle force at low-speed dynamics. Patients underwent comprehensive warm-up sessions under the guidance of professional testers (J.S. and Y.Z.) to conduct the knee joint isokinetic muscle strength test with adaptive training, ensuring full adaptation before the formal assessment. The patient assumed a seated position on the testing chair, with the torso and the test leg secured by safety belts, aligning the direction of the test knee joint with that of the power arm. The range of motion for the knee was individualized for each patient, and the angular velocity of knee flexion and extension movements was standardized at 60 deg/sec for the assessment, commencing with testing the healthy side, followed by the affected side. To facilitate analysis, the limb symmetry index (LSI) was utilized to express the ratio of peak moments of the extensor and flexor muscle groups on the affected side relative to those on the healthy side (hamstring-to-quadriceps ratio [H/Q]).

Figure 2.

Schematic diagram of isokinetic muscle strength testing.

Hop Test

Three functional tests were chosen: (1) the single-leg hop test; (2) the single-leg triple hop test; and (3) the single-leg cross-over hop test (Figure 3). Before each test, the examiner (J.S. and Y.Z.) explained and demonstrated the procedures to the participants to acquaint them with the testing protocol and movements. Participants practiced each movement on both legs before the official assessment to familiarize themselves with the procedures. A successful attempt was defined as the participant maintaining the jump for at least 2 seconds after landing. Each test was repeated 3 times, and the distance achieved was recorded, with a precision of 1 cm. If the distance achieved on the third attempt was greater than previous attempts, a fourth attempt was conducted, and if the fourth attempt exceeded all previous distances, it was included in the data analysis. Test failure was defined as any instance where the participant’s contralateral lower or upper limb made contact with the ground, loss of balance occurred, or an additional jump was made upon initial landing. The time interval between attempts of the same test was 30 seconds, while the time interval between different test items was 2 minutes.

Figure 3.

Schematic diagram of the hop test.¹¹

Y-Balance Test

The YBT exercise kit (The Functional Movement Screen) was positioned on a level testing surface. The angle formed between the anterior lateral tube of the YBT kit and the posterior medial and posterior lateral tubes was set at 135°, while the angle between the posterior medial and posterior lateral tubes was set at 90°. The central area encompassed by all 3 directions constituted the support leg standing area.

Participants stood barefoot on a force platform equipped with the YBT kit, positioning 1 leg with the big toe aligned behind the center horizontal line and directly facing the subject, while the hands were crossed (Figure 4). The other leg sequentially extended in the anterior, posterolateral, and posteromedial (PM) directions, with the distance of each extension recorded in centimeters (cm). After 3 extensions in each direction, the direction of extension was rotated.

Figure 4.

Schematic diagram of YBT.

Before the formal test, participants engaged in corresponding warm-up activities. They practiced each directional extension 3 times to acquaint themselves with the movements. The formal assessment commenced after a 5-minute rest period. If a participant failed to extend in any direction during all 3 attempts, the distance was recorded as 0 cm. Testers were prohibited from utilizing the block as a support for the forward-extended leg. Failures were defined as instances of balance loss while standing on 1 leg, significant movement of the standing foot, the extended foot making contact with the ground for support, or failure of the extended leg to return to its initial position. These instances were not included in the data analysis.

Safe Return to Sports

Meredith et al²² defined RTS as a return to the type, intensity, frequency, and quality of performance as before the injury; thus, in this study, RTS was judged according to whether the postoperative Tegner athletic ability evaluation score and the Marx Activity Rating Scale reached the preinjury level. It has been found¹⁰ that when certain criteria are met, the knee reinjury rate when patients return to sports is reduced by 84%, suggesting that the criteria for RTS safely should include postoperative time, subjective outcome scores, objective assessment of knee function, and psychological readiness assessment. Therefore, the following safe RTS criteria were determined in this study in conjunction with related studies^1,3,5,32: (1) postoperative time ≥9 months; (2) lower extremity maximal muscle strength LSI ≥85%; (3) ACL-RSI >65; (4) jump test LSI ≥85%; (5) Y-balance LSI ≥85%; and (6) Tegner score restored to the preinjury level. Anyone who did not fulfill any of the above was considered to have failed to return to sport safely.

Statistical Analysis

SPSS 26.0 (SPSS Inc) statistical software was used to analyze the data. Continuous variables were expressed as means ± standard deviations, and categorical variables were expressed as numbers or percentages. All continuous variables were judged for normality using the Kolmogorov-Smirnov test, and combined with probability-probability and quantile-quantile plots. If the variables were normally distributed, they were compared between groups using an independent samples t test. All noncontinuous variables were compared between groups using the chi-square test. P < .05 was considered statistically significant.

Results

Patient Characteristics

Table 1 summarizes patient characteristics of the 2 groups. Based on the results of the PST performed by 2 surgeons specialized in sports medicine at a senior level, 81 patients were included, with a mean age of 31.47 ± 8.35 years (range, 14-48 years), and a mean follow-up of 4.19 ± 2.48 years, including 57 male (70%) and 24 female patients (30%). A total of 42 patients (52%) had negative PST results (SG), while 46 patients (48%) had positive PST results (MIG). No significant differences were found between the 2 groups in terms of sex, age at surgery, BMI, time from injury to surgery, affected side, and meniscal injury.

Table 1

Patient Characteristics ^a

	SG, N = 42	MIG, N =39	P
Sex, male/female	32/10	24/15	.093
Age at surgery, y	31.50 ± 8.74	31.44 ± 8.03	.973
BMI, kg/m²	24.70 ± 3.19	24.10 ± 3.12	.393
Time from injury to surgery, days	176.57 ± 361.37	156.54 ± 357.47	.803
Injury side, left/right	28/14	22/17	.343
Follow-up time, y	3.71 ± 2.25	4.72 ± 2.62	.064
Meniscal injuries
None	13 (31)	13 (33.3)	.994
Medial	17 (40.5)	15 (38.5)
Lateral	8 (19)	7 (17.9)
Medial and lateral	4 (9.5)	4 (8.6)
Meniscal treatment
Meniscectomy	19	11	.094
Repair	14	11	.094
Preinjury Tegner	6.52 ± 1.35	6.41 ± 0.75	.644
Preinjury Marx	12.10 ± 4.51	10.87 ± 3.65	.185

Data are presented as mean ± SD or n (%). BMI, body mass index; MIG, mild rotational laxity group; SG, stable group.

Anteroposterior Laxity of the Knees

The results of the KT-2000 joint kinematics are shown in Table 2. The results showed that the KT-2000 SSD on the healthy side and the affected side of the SG were smaller than that of the MIG; nonetheless, the difference was not statistically significant.

Table 2

Comparison of the Difference in the Anteroposterior Laxity of the Knees Between the 2 Groups ^a

	SG (n = 42)	MIG (n = 39)	P
KT-2000 SSD, mm	1 ± 1.48	1.44 ± 1.76	.230

Data are presented as mean ± SD. MIG, mild rotational laxity group; SG, stable group; SSD, side-to-side difference.

Outcomes

No significant difference was observed in the Lysholm, Marx, IKDC, KOOS, and Marx scores between the 2 groups. However, the ACL-RSI score and the Tegner motor level were significantly higher in the SG than in the MIG (69.54 ± 21.34 vs 56.70 ± 19.51; P = .006; 5.81 ± 1.70 vs 4.95 ± 1.93; P = .036) (Table 3).

Table 3

Comparison of Subjective Scores Between the 2 Groups ^a

	SG (n = 42)	MIG (n = 39)	P
Lysholm	82.40 ± 17.17	80.82 ± 14.77	.659
IKDC	81.76 ± 12.77	79.27 ± 12.01	.370
KOOS	82.54 ± 10.89	79.03 ± 12.13	.173
ACL-RSI	69.54 ± 21.34	56.70 ± 19.51	.006
Postop Tegner	5.81 ± 1.70	4.95 ± 1.93	.036
Postop Marx	8.14 ± 5.82	6.92 ± 4.98	.315

Data are presented as mean ± SD. ACL, anterior cruciate ligament; ACL-RSI, ACL-Return to Sport after Injury Score; IKDC, International Knee Documentation Committee; KOOS, Knee injury and Osteoarthritis Outcome Score; MIG, mild rotational laxity group; Postop, postoperative; SG, stable group.

Performance

A significant difference was observed between the 2 groups in terms of LSI in the jump test, with the SG having a higher LSI in the single-leg hop, triple hop, and cross-over hop test scores than the MIG (78.51 ± 29.62 vs 59.34 ± 37.61 [P = .013]; 83 ± 27.70 vs 65.04 ± 37.22 [P = .017]; 84.24 ± 27.39 vs 68.73 ± 39.69 [P = .046]), with no significant differences in any other aspects of performance (Table 4).

Table 4

Comparison of the Performance Between the 2 Groups ^a

	SG (n = 42)	MIG (n = 39)	P
Knee peak-time strength LSI, 60 deg/sec, %
Extension	77.83 ± 29.02	80.24 ± 39.91	.755
Flexion	89.16 ± 23.53	89.99 ± 31.56	.894
H/Q	0.59 ± 0.23	0.56 ± 0.25	.555
Hop test LSI, %
Single-leg hop	78.51 ± 29.62	59.34 ± 37.61	.013
Triple hop	83 ± 27.70	65.04 ± 37.22	.017
Cross-over hop	84.24 ± 27.39	68.73 ± 39.69	.046
YBT LSI, %
A	93.94 ± 9.27	88.61 ± 23.42	.191
PL	98.51 ± 8.58	93.18 ± 23.61	.175
PM	96.90 ± 9.38	91.48 ± 23.61	.187

Data are presented as mean ± SD. A, anterior; H/Q, hamstring-to-quadriceps; LSI, limb symmetry index; MIG, mild rotational laxity group; PL, posterior lateral; PM, posteromedial; SG, stable group; YBT, Y-balance test.

Return to Sports

In this study, the overall RTS rate was 37% (30/81). The RTS rate was 38.1% (16/42) in the SG and 35.9% (14/39) in the MIG. The safe RTS rate was 7.1% (3/42) in the SG, compared with 2.6% (1/39) in the MIG (Table 5). Among those patients who returned to sports, approximately 18.8% (3/16) in the SG met the criteria for a safe RTS, compared to just 7.1% (1/14) in the MIG. However, the difference was not statistically significant between the 2 groups.

Table 5

Comparison of RTS Between the 2 Groups ^a

	SG (n = 42)	MIG (n = 39)	P
RTS	38.1	35.9	.838
Safe RTS	7.1	2.6	.342

Data are presented as %. MIG, mild rotational laxity group; RTS, return to sports; SG, stable group;

Discussion

In this study, patients exhibiting negative PST demonstrated significantly enhanced levels of postoperative physical activity compared with the MIG. Furthermore, all metrics evaluating performance in the single-leg hop, triple hop, and cross-over hop tasks exhibited statistically significant elevations in patients with negative PST, as opposed to those with grade 1 PST. Moreover, the SG yielded significantly higher scores on the ACL-RSI scale compared with the MIG, indicating that knee laxity after ACLR may exert a substantial influence on knee function during the short and medium terms, as well as on the recovery process aimed at resuming athletic activities.

Hop tests are generally used to assess the neuromuscular control of the knee, which is poor in ACLR knees during jump landings.⁷ Among the 3 jump tests, the single-leg jump test is more sensitive for assessing return to motion after ACLR,¹² and the results of the triple and cross-over hop tests are strongly correlated with the recovery of muscle strength of the quadriceps and hamstrings in the lower extremity; nonetheless, the association with the rotational laxity of the knee is not clear.² In this study, no significant difference was observed in the 60 deg/sec isometric muscle strength test between the 2 groups, and the H/Q ratio was similar on the affected side (0.59 vs 0.56; P > .05), whereas the LSI of the hop test in the SG was significantly higher than that of the MIG, which suggests that knee stabilization during dynamic activities affects the function of neuromuscular control, and this functional deficit may result in excessive damage to ligaments, excessive loading on such structures as the joint capsule, and ultimately increasing the risk of ACL reinjury.³² In other words, this hop test could be used to make a tentative judgment about laxity and objectively evaluate the efficacy of ACLR and the safety of RTS. In previous studies, Jonsson et al¹⁵ found that the difference between the single-leg hop test results of patients with negative PST results and those of patients with positive PST results was not statistically significant at 5 to 9 years of follow-up. Sundemo et al²⁹ found that the single-leg hop test results of patients with negative PST were better than those of patients with positive PST results at the 2-year postoperative follow-up after ACLR; nevertheless, the difference in findings was not significant, whereas a significant difference was observed at 16 years.

The ACL-RSI scale has been recognized as a reliable and valid tool for evaluating RTS in recent years. In the present study, the ACL-RSI scores of the SG were significantly higher than those of the MIG (69.54 ± 21.34 vs 53.60 ± 21.67; P = .001). According to the Albano¹ standard for ACL-RSI scores in RTS, 54.8% of the SG met the standard, compared with just 35.9% of the MIG. This result suggests that the rotational laxity of the knee after ACLR may influence the psychological status during RTS. Faleide et al⁴ showed that the degree of laxity of the knee could be predicted by the ACL-RSI scores, and the psychological scores of the lax knee scores were lower. McPherson et al²¹ hypothesized that this was due to the fear of reinjury caused by the inherent instability of the knee, which lowered the psychological score. In contrast, Webster et al³⁰ found no association between the degree of anteroposterior laxity of the knee and ACL-RSI scores in a 1-way correlation analysis. However, this may be because the patients included in the study were all athletes or sportsmen with high basal muscle strength, which compensated to a certain extent for the mechanical laxity of the knee through plyometric and neuromuscular feedback, thus creating this difference. Thus, the results of this study may not apply to the general population. Psychological monitoring is often overlooked in rehabilitation. This study shows that the ACL-RSI score is associated with knee rotational laxity postoperation, emphasizing the need to address psychological readiness during rehabilitation.

The ultimate goal of testing on performance is also to assess the safety of patients to RTS. RTS is characterized by achieving the preinjury level of sports participation as defined by the same type, frequency, intensity, and quality of performance as before injury in the Panther Consensus.²² Grindem et al¹⁰ found that even when patients returned to sports after ACLR, they still had a high risk of reinjury, while when certain criteria were met, the rate of knee reinjury when patients returned to sports was reduced by 84%. In this study, the RTS rate in the SG was 38.1% (16/42), of which 18.8% (3/16) met the safe RTS criteria, while the RTS rate in the MIG was 35.9% (14/39), of which 7.1% (1/14) met the safe RTS criteria; however, none of the differences between the groups were statistically significant. The rate of meeting safe RTS criteria was approximately 3 times higher in the SG than in the MIG, and even though the difference between the groups was not significant, the authors concluded that the role of rotational laxity of the knee on safe RTS still could not be ignored. The results of this study showed that patients in the SG had significantly higher postoperative Tegner scores than those in the MIG, and that patients with stable knees had a high level of athletic ability, suggesting that return to preinjury levels may be easier with a stable knee. Zhou et al³² showed that patients who did not meet the safe return criteria postoperatively had greater lateral tibial translation distances and more pronounced external tibial rotational angles. This seems to indicate that the restoration of knee rotational laxity after ACLR is important for safe RTS.

In addition, the present study found that the percentage of patients who met the criteria for RTS safely was low, regardless of knee stabilization. A study by Sheean et al²⁷ showed that even if postoperative patients were able to RTS, there was a higher likelihood of reinjury due to functional deficits or insufficient recovery. The results of this study showed a significant decrease in the Marx scores of all postoperative patients, suggesting that the reconstructive surgery affected the patients’ lives and exercise habits, and most of the patients exercised less frequently. The results of the study by Longstaffe et al¹⁹ showed that the RTS rate after ACLR in professional soccer players was 69.8%, which was significantly higher than the RTS rate in the results of the present study. This is mainly due to the difference in the study population. Lindanger et al^18,19 also suggested that postoperative rehabilitation is one of the most important factors influencing RTS participation, and rehabilitation under the supervision of a professional rehabilitation therapist is more effective than self-rehabilitation or no rehabilitation at all.⁹ However, the goal of professional athletes after surgery is to RTS as soon as possible as well as to regain their original level of competition, and they usually have more comprehensive medical care, receive continuous and individualized rehabilitation and fitness-specific training, et cetera. These are the reasons why the rate of athletes’ RTS is higher than that of the general population in the present study; nonetheless, there are few reports on whether athletes who RTS meet the criteria of safe RTS, and it needs to be explored in greater depth. The results suggest that clinicians should further strengthen patient education, guide patients to set correct rehabilitation goals, and fully inform patients about the importance of postoperative rehabilitation for functional recovery and RTS to encourage them to adhere to rehabilitation training for a safe RTS.

There are certain strengths of this study. Most current reports on knee laxity after ACLR focus on short-term follow-ups and anteroposterior laxity. This study, however, examines the effect of rotational laxity on RTS with a longer follow-up of 2 to 15 years, incorporating PST results. In addition, the present study was more specific about RTS, not only using questionnaires, but also taking into account the objective performance of various aspects of sports, including lower extremity muscle strength tests, hop tests, and YBTs.

Limitations

There are some limitations to this study. First, the PST is a subjective assessment, and there may be bias or inaccurate results due to the patient's muscle tension during the test. However, in this study, the tests were initially conducted without anesthesia by 2 sports medicine experts separately. If the results were inconsistent, further testing was performed under anesthesia to minimize this potential error as much as possible. In addition, our population was not composed of athletes, and that likely could have affected observations of activity levels. Moreover, we have set stricter criteria for assessment of “safe RTS,” thus, comparison to other studies with different criteria may not be valid.

Meanwhile, this was a study with a short-to-medium-term follow-up, and a long-term follow-up will also be conducted.

Conclusion

Mild rotational laxity of the knee after ACLR results in poorer performance in single-leg hop, triple hop, and cross-over hop tests as well as lower-level athletic ability. Patients with stabilized knees had higher ACL-RSI scores than unstable patients, and the stabilized group scored at the return-to-exercise standard while the unstable group did not. In addition, the rotational stability of the knee significantly affected patients’ postoperative exercise levels, with rotational instability of the knee showing lower levels of exercise. In the general population, RTS rates were lower in the short- to medium-term after ACLR, regardless of rotational stability, with most patients failing to meet safe RTS criteria.

Footnotes

Final revision submitted February 10, 2025; accepted March 17, 2025.

The authors have declared that there are no conflicts of interest in the authorship and publication of this contribution. AOSSM checks author disclosures against the Open Payments Database (OPD). AOSSM has not conducted an independent investigation on the OPD and disclaims any liability or responsibility relating thereto.

Ethical approval for this study was obtained from the Regional Ethics Committee (202210), National Institute of Sports Medicine.

ORCID IDs

Jingyi Sun

Yingqi Zhao

Feng Gao

Jingbin Zhou

References

Albano

Rodrigues

CAS

Melo

AKP

de Paula

Almeida

GPL

. Clinical decision algorithm associated with return to sport after anterior cruciate ligament reconstruction. J Athl Train. 2020;55(7):691-698. doi:10.4085/1062-6050-82-19

Al-Gburi

Kristiansen

Christensen

Krogsgaard

MR.

Functional performance tests, clinical measurements, and patient-reported outcome measures do not correlate as outcomes 1 year after anterior cruciate ligament reconstruction. Knee Surg Sports Traumatol Arthrosc. 2023;31(12):5905-5912. doi:10.1007/s00167-023-07648-w

Burgi

Peters

Ardern

, et al. Which criteria are used to clear patients to return to sport after primary ACL reconstruction? A scoping review. Br J Sports Med. 2019;53(18):1154-1161. doi:10.1136/bjsports-2018-099982

Faleide

AGH

Magnussen

Bogen

, et al. Association between psychological readiness and knee laxity and their predictive value for return to sport in patients with anterior cruciate ligament reconstruction. Am J Sports Med. 2021;49(10):2599-2606. doi:10.1177/03635465211021831

Fältström

Hägglund

Kvist

Patient-reported knee function, quality of life, and activity level after bilateral anterior cruciate ligament injuries. Am J Sports Med. 2013;41(12):2805-2813. doi:10.1177/0363546513502309

Galway

MacIntosh

DL.

The lateral pivot shift: a symptom and sign of anterior cruciate ligament insufficiency. Clin Orthop Relat Res. 1980;(147):45-50.

Georgoulis

Melissaridou

Patras

, et al. Neuromuscular activity of the lower-extremities during running, landing and changing-of-direction movements in individuals with anterior cruciate ligament reconstruction: a review of electromyographic studies. J Exp Orthop. 2023;10(1):43. doi:10.1186/s40634-023-00603-1

Getgood

AMJ

Bryant

Litchfield

, et al. Lateral extra-articular tenodesis reduces failure of hamstring tendon autograft anterior cruciate ligament reconstruction: 2-year outcomes from the STABILITY study randomized clinical trial. Am J Sports Med. 2020;48(2):285-297. doi:10.1177/0363546519896333

Glattke

Tummala

Chhabra

Anterior cruciate ligament reconstruction recovery and rehabilitation: a systematic review. J Bone Joint Surg Am. 2022;104(8):739-754. doi:10.2106/JBJS.21.00688

10.

Grindem

Snyder-Mackler

Moksnes

Engebretsen

Risberg

MA.

Simple decision rules can reduce reinjury risk by 84% after ACL reconstruction: the Delaware-Oslo ACL cohort study. Br J Sports Med. 2016;50(13):804-808. doi:10.1136/bjsports-2016-096031

11.

Güzel

Genç

Yılmaz

Kehribar

The relationship between lower extremity functional performance and balance after anterior cruciate ligament reconstruction: results of patients treated with the modified all-inside technique. J Pers Med. 2023;13(3):466. doi:10.3390/jpm13030466

12.

Qiu

Cao

, et al. Effects of deficits in the neuromuscular and mechanical properties of the quadriceps and hamstrings on single-leg hop performance and dynamic knee stability in patients after anterior cruciate ligament reconstruction. Orthop J Sports Med. 2022;10(1):23259671211063893. doi:10.1177/23259671211063893

13.

Inclan

Brophy

RH.

Revision anterior cruciate ligament reconstruction. Bone Joint J. 2023;105-B(5):474-480. doi:10.1302/0301-620X.105B5.BJJ-2022-1064.R1

14.

Jakob

Stäubli

Deland

JT.

Grading the pivot shift. Objective tests with implications for treatment. J Bone Joint Surg Br. 1987;69(2):294-299.

15.

Jonsson

Riklund-Ahlström

Lind

Positive pivot shift after ACL reconstruction predicts later osteoarthrosis: 63 patients followed 5-9 years after surgery. Acta Orthop Scand. 2004;75(5):594-599.

16.

Kim

Hwang

Choi

, et al. Correlation between Y-balance test and balance, functional performance, and outcome measures in patients following ACL reconstruction. Int J Sports Phys Ther. 2022;17(2):193-200. doi:10.26603/001c.31873

17.

Lindanger

Strand

Mølster

Solheim

Inderhaug

Effect of early residual laxity after anterior cruciate ligament reconstruction on long-term laxity, graft failure, return to sports, and subjective outcome at 25 years. Am J Sports Med. 2021;49(5):1227-1235. doi:10.1177/0363546521990801

18.

Lindanger

Strand

Mølster

Solheim

Inderhaug

Return to play and long-term participation in pivoting sports after anterior cruciate ligament reconstruction. Am J Sports Med. 2019;47(14):3339-3346. doi:10.1177/0363546519878159

19.

Longstaffe

Leiter

Gurney-Dunlop

McCormack

MacDonald

Return to play and career length after anterior cruciate ligament reconstruction among Canadian professional football players. Am J Sports Med. 2020;48(7):1682-1688. doi:10.1177/0363546520918224

20.

Magnussen

Reinke

Huston

, et al. Neither residual anterior knee laxity up to 6 mm nor a pivot glide predict patient-reported outcome scores or subsequent knee surgery between 2 and 6 years after ACL reconstruction. Am J Sports Med. 2021;49(10):2631-2637. doi:10.1177/03635465211025003

21.

McPherson

Feller

Hewett

Webster

KE.

Smaller change in psychological readiness to return to sport is associated with second anterior cruciate ligament injury among younger patients. Am J Sports Med. 2019;47(5):1209-1215. doi:10.1177/0363546519825499

22.

Meredith

Rauer

Chmielewski

, et al. Return to sport after anterior cruciate ligament injury: Panther Symposium ACL Injury Return to Sport Consensus Group. Knee Surg Sports Traumatol Arthrosc. 2020;28(8):2403-2414. doi:10.1007/s00167-020-06009-1

23.

Meyer

CAG

Gette

Mouton

Seil

Theisen

. Side-to-side asymmetries in landing mechanics from a drop vertical jump test are not related to asymmetries in knee joint laxity following anterior cruciate ligament reconstruction. Knee Surg Sports Traumatol Arthrosc. 2018;26(2):381-390. doi:10.1007/s00167-017-4651-2

24.

Michel

Jordan

Canovas

Bouchdoug

Dagneaux

Gaillard

Influence of residual anterior laxity on functional outcomes after anterior cruciate ligament reconstruction. Orthop Traumatol Surg Res. 2022;108(3):103264. doi:10.1016/j.otsr.2022.103264

25.

Noyes

Huser

Levy

MS.

The effect of an ACL reconstruction in controlling rotational knee stability in knees with intact and physiologic laxity of secondary restraints as defined by tibiofemoral compartment translations and graft forces. J Bone Joint Surg Am. 2018;100(7):586-597. doi:10.2106/JBJS.16.01412

26.

O’Connor

King

Richter

Webster

Falvey

ÉC

. No Relationship between strength and power scores and anterior cruciate ligament return to sport after injury scale 9 months after anterior cruciate ligament reconstruction. Am J Sports Med. 2020;48(1):78-84. doi:10.1177/0363546519887952

27.

Sheean

Jin

Huston

, et al. Predictors of return to activity at 2 years after anterior cruciate ligament reconstruction among patients with high preinjury Marx activity scores: a MOON prospective cohort study. Am J Sports Med. 2023;51(9):2313-2323. doi:10.1177/03635465231172769

28.

Snoeker

Turkiewicz

Magnusson

, et al. Risk of knee osteoarthritis after different types of knee injuries in young adults: a population-based cohort study. Br J Sports Med. 2020;54(12):725-730. doi:10.1136/bjsports-2019-100959

29.

Sundemo

Sernert

Kartus

, et al. Increased postoperative manual knee laxity at 2 years results in inferior long-term subjective outcome after anterior cruciate ligament reconstruction. Am J Sports Med. 2018;46(11):2632-2645. doi:10.1177/0363546518786476

30.

Webster

Nagelli

Hewett

Feller

JA.

Factors associated with psychological readiness to return to sport after anterior cruciate ligament reconstruction surgery. Am J Sports Med. 2018;46(7):1545-1550. doi:10.1177/0363546518773757

31.

Zhang

Qian

Gao

, et al. High anteromedial insertion reduced anteroposterior and rotational knee laxity on mid-term follow-up after anatomic anterior cruciate ligament reconstruction. PeerJ. 2023;11:e15898. doi:10.7717/peerj.15898

32.

Zhou

Zhang

, et al. Multiplanar knee kinematics-based test battery helpfully guide return-to-sports decision-making after anterior cruciate ligament reconstruction. Front Bioeng Biotechnol. 2022;10:974724. doi:10.3389/fbioe.2022.974724

The Effect of Mild Residual Rotational Laxity on Performance After Anterior Cruciate Ligament Reconstruction

Abstract

Background:

Purpose:

Study Design:

Methods:

Results:

Conclusion:

Keywords

Methods

Participants

Clinical Examination

Pivot Shift Test

KT-2000

Lower Extremity Muscle Strength

Hop Test

Y-Balance Test

Safe Return to Sports

Statistical Analysis

Results

Patient Characteristics

Anteroposterior Laxity of the Knees

Outcomes

Performance

Return to Sports

Discussion

Limitations

Conclusion

Footnotes

ORCID IDs

References