Back on track, but still benched: Long-term impact of patellar dislocation on sport and function – A retrospective cohort study

Jesper Lykkegård Toustrup; Niklas Diget; Bogi Sørensen; Henrik Riel; Carsten Møller Mølgaard

doi:10.1016/j.jor.2025.12.012

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73 (); 303-309

doi:

10.1016/j.jor.2025.12.012

Back on track, but still benched: Long-term impact of patellar dislocation on sport and function – A retrospective cohort study

Jesper Lykkegård Toustrup^a,b,, Niklas Diget^b, Bogi Sørensen^b, Henrik Riel^b,d, Carsten Møller Mølgaard^a,b,c

a Department of Physiotherapy and Occupational Therapy, Aalborg University Hospital, Hobrovej 18-22, 9000, Aalborg, Denmark

b Department of Health Science and Technology, Faculty of Medicine, Aalborg University, Selma Lagerløfs Vej 249, 9260, Gistrup, Denmark

c Department of Orthopedic Surgery, Aalborg University Hospital, Hobrovej 18-22, 9000, Aalborg, Denmark

d Department of Physiotherapy, University College of Northern Denmark, Selma Lagerlöfs Vej 2, 9220, Aalborg, Denmark

⁎Corresponding author: Jesper Lykkegård Toustrup. jespert49@gmail.com

Received: 2025-10-24, Accepted: 2025-12-7, Published: 2025-12-8

The Authors

Disclaimer:
This article was originally published by Reed Elsevier India Pvt. Ltd. and was migrated to Scientific Scholar after the change of Publisher.

Abstract

To assess the long-term clinical outcomes following patellar dislocation, including patients with primary and recurrent dislocations and those treated surgically.

A retrospective cohort study of patients with patellar dislocation between January 2019 and December 2022. Participants completed a questionnaire >6 months after their most recent dislocation or >1 year following patellar stabilization surgery. The primary outcome was the Kujala score. Secondary outcomes included the Tegner Activity Scale, Knee Self-Efficacy Scale (K-SES), Patient Acceptable Symptom State (PASS), and the Sporting Activity Questionnaire (SAQ). Comparisons were made between primary dislocations, recurrent dislocations, and those who underwent surgery.

228 participants were included: 66 with primary dislocation, 88 with recurrent dislocations, and 74 who had undergone surgery. The median Kujala score was 89 (78–96) for primary, 82 (72–92) for recurrent, and 78 (65–89) for the surgical group (p < 0.001). The SAQ showed a decline in high-impact sport participation and an increase in no sport participation from pre-to post-injury. These changes were statistically significant in the recurrent group (p < 0.001) and the surgery group (p < 0.001), but not in the primary group (p = 0.143). According to PASS, 49 % of participants reported dissatisfaction with their current knee function.

Patellar dislocations may cause long-term physical limitations and reduced sports participation, with about half of patients dissatisfied with knee function after 2–3 years. Surgery does not appear sufficient to restore patients to full physical function.

Keywords

Patellar dislocation

Patellar instability

Knee function

Patient-reported outcome

Sports participation

TT-TG

REDCap

K-SES

PASS

SAQ

IKDC

SD

IQR

MCID

MRI

ESSKA

1 Introduction

Patellar dislocation is a common orthopaedic injury, particularly in adolescents, and often occurs during sports.¹^,² It accounts for 3.3 % of all knee injuries and substantially burdens healthcare systems and individuals, affecting their ability to participate in physical activities and social life.³^,⁴ Numerous studies have identified key risk factors for recurrence, including trochlear dysplasia, patella alta, and younger age.⁵^,⁶ However, uncertainty remains regarding the optimal treatment for achieving the best outcomes,⁷^,⁸ with the ESSKA consensus statement highlighting the low quality of evidence in this population.⁹^,¹⁰ A central question is whether surgical or non-operative treatment is preferable. Generally, conservative treatment is recommended after a primary dislocation,¹¹ whereas surgery is considered after a second dislocation.⁷ Although recent reviews indicate a current shift toward surgical treatment.⁸^,¹²^,¹³

Most studies use recurrence as one of the primary outcome measures for treatment efficacy, but relying solely on dislocation recurrence is inadequate.¹⁴ Studies indicate that some patients without recurrent dislocations continue to experience physical limitations.¹⁴^,¹⁵ One study reported that only 26 % returned to activities without limitations after a primary patellar dislocation,¹⁴ while another found that over 30 % did not return to sport within 6 months.¹⁵ This is of particular concern, as reduced lower-extremity function predicts radiographic knee osteoarthritis within five years in adults with chronic knee pain.¹⁶ Additionally, adolescents with patellofemoral pain often continue to experience symptoms into adulthood.¹⁷ The incidence of patellar dislocation is particularly high among adolescents, whereas participating in sporting activities plays a major part in engagement in physical activity, psychological well-being, and social life.¹⁸ Reducing or ceasing engagement in physical activity because of knee pain may lead to an inactive lifestyle, poorer fitness, and health status.¹⁹^,²⁰

Altogether, this highlights the importance of a comprehensive long-term assessment of clinical outcomes, including patient-reported physical function, patient satisfaction, and participation in sporting and recreational activities. Such insights would be valuable for understanding the prognosis and long-term consequences of patellar dislocation. Therefore, this study aimed to assess long-term clinical outcomes in patients with primary, recurrent, and surgically treated patellar dislocations.

2 Materials and methods

2.1

2.1 Study design and recruitment

We conducted a survey-based retrospective cohort study in participants with a prior patellar dislocation. All patients with patellar dislocation treated at Aalborg University Hospital between January 1, 2019 and December 31, 2022 were contacted. Participants were eligible for inclusion if they had suffered a primary dislocation, recurrent dislocation(s), or had received patellar stabilization surgery. The exclusion criteria were: 1) latest patellar dislocation <6 months or patellar stabilization surgery <1 year ago; 2) other competing disorders limiting sports or recreational participation; 3) other previous knee injuries (e.g., ACL injury) or 4) age <15 years old. Patients were identified via the Danish National Patient Registry using ICD-11 codes: DS830; DM221; DM220. In this period, 316 patients were classified with primary patellar dislocation, 697 with recurrent dislocation, and 19 with patellar subluxation. Participants were contacted via Digital mailbox (e-Boks) containing a link to questionnaires. We used Research Electronic Data Capture (REDcap) – a secure web‐based software platform designed to support data capture. Non-responders received a reminder after seven days and a follow-up phone call after another seven days.

The local Ethics Committee confirmed that approval was not required since this was an observational study under Danish law (Committee Law Section 14(1), cf. Section 2(1)). The Danish Data Protection Agency approved the study (J.nr. K2024-074). The study was reported according to STROBE guidelines 20. Informed consent was obtained digitally from all participants at the start of the survey.

2.2

2.2 Initial treatment for patients with primary patellar dislocation

At first hospital contact, an X-ray is performed to detect any fractures. Treatment includes a Don Joy brace (0–30° knee mobility) for 14 days. Immediate full weight bearing is allowed as tolerated. After 14 days, patients are examined at the orthopedic clinic for potential referral to specialized rehabilitation. Rehabilitation includes strength and functional training, joint mobilization, and patient education. Full participation in contact sports is not recommended until 6 months after injury.

2.3

2.3 Demographics, injury history, and patella morphology

The participants' demographic and injury history data were collected, including sex, current age, age at first dislocation, age at last dislocation, number of dislocations, bilateral dislocations, time since first dislocation, time since the last dislocation, and whether they received surgery. Additionally, the number of hospital contacts since the first visit to the emergency department was accounted for in categories (0, 1–5, 6–10, and 10+). Participants were asked to identify the injury mechanism of their first dislocation by selecting the category that best matched the situation: low-intensity, high-intensity without contact, or high-intensity with contact. The patella height was measured using X-rays from the first visit to the Emergency Medicine and Trauma Center, using the Caton-Deschamps index ratio.²¹ Three physiotherapists (BS, JLT, ND) conducted the measurements after receiving training from an experienced physiotherapist (CMM).

2.4

2.4 Clinical outcomes

The following clinical outcome measures were collected ≥6 months after the last dislocation or ≥1 year after patellar stabilization surgery, defining the post-injury period.

Kujala score: The primary clinical outcome was the Kujala score. It is a 13-item questionnaire for assessing the severity of symptoms and physical limitations in people with patellofemoral pain.²² It is one of the most commonly used PROMs and has demonstrated excellent responsiveness.⁸^,⁹^,²³ The score ranges from 0 to 100, with higher scores indicating fewer symptoms. The minimal clinically important difference (MCID) is identified at 10 points.²⁴

Sporting activity questionnaire (SAQ): This questionnaire was used to assess participants' sporting activity pre- and post-injury or surgery to detect changes in the type of sporting activity.²⁵^,²⁶ All activities were categorized into three groups: high-impact activities (soccer, handball, basketball, etc.), low-impact activities (cycling, hiking, Nordic walking, fitness training, etc.), or no sports.²⁵ It was possible to name up to three activities per participant. A “Yes"/"No” question was added to this questionnaire about whether changes in sports discipline were related to their knee injury.

Tegner Activity Scale: The participants' current work and sports activity participation level was measured using a numerical scale (0−10), with each value representing specific sports activities.²⁷^,²⁸

Knee self-efficacy (K-SES): Measured using the Knee Self-Efficacy Scale (0–10, with 10 being the highest self-efficacy).²⁹^,³⁰

Patient Acceptable Symptom State (PASS): Patients' satisfaction with their current knee function was measured with PASS, previously used in Thorlund et al.,³¹ which involves the question: “When you think about your knee function, would you assess your current condition as satisfactory? Consider your daily activities, sports and recreational activities, your pain, and other symptoms, as well as your quality of life when evaluating knee function.” (Response option “yes” or “no”).

2.5

2.5 Statistical analyses

The statistical analyses were performed using Stata version 18.0 (Stata Corp LLC, Texas, United States of America). Continuous data are presented with mean (standard deviation, SD) for normally distributed data and median (interquartile range, IQR, 25 %–75 % quartile) for non-normally distributed data. Normal distribution was tested using histograms. Categorical data are presented with frequencies and percentages.

To investigate differences in the primary outcome (Kujala score) and the secondary outcomes (K-SES, Tegner, and PASS) between the three subgroups (primary dislocation group, recurrent dislocation group, and surgery group), the Kruskal-Wallis H test was used, as the assumptions of normality and homogeneity of variances were violated. Post-hoc pairwise comparisons were conducted using the Wilcoxon rank-sum test with a Bonferroni correction to account for multiple comparisons. Results from the SAQ are presented with the number and percentage of participants in the three sport participation categories (high-impact, low-impact, and no sport) and the number participating in specific sports and recreational activities from pre-to post-injury. To assess statistically significant changes in the distribution of sport participation categories from pre-to post-injury, a chi-square test of independence was performed separately for each subgroup (primary dislocation, recurrent dislocation, and surgery). Pre- and post-injury responses were structured in long format to allow for comparison across time points. Statistical significance was set at p ≤ 0.05.

3 Results

A total of 978 people were identified by ICD-codes (Fig. 1), whereas 810 were eligible for participation. Of these, 401 completed the demographic section of the questionnaire and the Kujala score, resulting in a response rate of 49.5 %. Following further exclusion, 228 participants were included in the analysis (Fig. 1). Two hundred twenty-seven answered Tegner, 219 the KSES, 215 the PASS, 207 the SAQ, and 214 had their patella height measured. Data were collected from April 9, 2024 to April 30, 2024. The 228 included participants comprised 66 in the primary group, 88 in the recurrent group, and 74 in the surgery group, with descriptive statistics of demographics, injury history, and patella height presented in Table 1.

Flowchart of participant enrollment: from ICD-11 identification to inclusion in the analysis of the Kujala score.

Table 1 Participant demographics, injury history and patella morphology.

	Primary dislocation	Recurrent dislocation	Surgery	Overall
Participants, n	66	88	74	228
Sex, n (%) male	36 (54.6)	27 (30.7)	20 (27)	83 (36.4)
Age, mean (SD)	24.6 (7.9)	25.8 (10.2)	26.4 (8.7)	25.6 (9.1)
Age at first dislocation, mean (SD)	21.6 (8.1)	16.25 (6.2)	15.6 (6.5)	17.7 (7.3)
Age at last dislocation, mean (SD)	21.6 (8.1)	23.8 (9.9)	23.1 (8.8)	23 (9.1)
Years since first dislocation, median (IQR)	3 (2–4)	6 (4–10.5)	9 (5–13.8)	5 (3–10)
Years since last dislocation, median (IQR)	3 (2–4)	2 (1–3)	2 (1–4)	2 (1–4)
Number of dislocations, median (IQR)	1	3 (2–5,5)	5 (3–8)	2 (1–5)
Bilateral dislocations, n (%)	0 (0)	39 (44.3)	28 (37.8)	67 (29.4)
Hospital contacts, n (%)
0	5 (7.6)	4 (4.6)	1 (1.3)	10 (4.3)
1 to 5	43 (65.1)	56 (63.6)	26 (35.1)	125 (54.8)
6 to 10	9 (13.6)	14 (15.9)	14 (18.9)	37 (16.2)
10+	9 (13.6)	14 (15.9)	33 (44.5)	56 (24.6)
Injury mechanism at first dislocation, n (%)
Low intensity	19 (28.8)	25 (28.4)	18 (24.3)	62 (27.2)
High intensity without contact	36 (54.5)	47 (53.4)	45 (60.8)	128 (56.1)
High intensity with contact	11 (16.7)	16 (18.2)	11 (14.9)	38 (16.7)
Patella height, n	63	82	69	214
Caton-Deschamps index, mean (SD)	1.14 (0.2)	1.18 (0.14)	1.22 (0.2)	1,18 (0.17)

The median time since last dislocation was 2 years (IQR: 1–4), with a median Kujala score of 84 (IQR: 70–93). The Kujala score for the three groups was 89 (IQR: 78–96) for primary dislocation, 82 (IQR: 72–92) for recurrent dislocation, and 78 (IQR: 65–89) for surgery. The Kruskal-Wallis H test showed a statistically significant difference in Kujala scores between the three groups (H(2) = 18.25, p < 0.001, as presented in Table 2). Post-hoc pairwise comparisons showed significantly better Kujala scores in the primary dislocation group compared to both the recurrent dislocation group (p = 0.017) and the surgery group (p < 0.001). No significant difference was found between the recurrent dislocation and surgery groups (p = 0.177).

Tabel 2 Differences in clinical outcomes between the three groups primary dislocation, recurrent dislocation and surgery at a median of 5 years (IQR: 3–10) since first dislocation.

	Overall	Primary dislocation	Recurrent dislocation	Surgery	p-value
Kujala score^a, nMedian (IQR)	22884 (70–93)	6689 (78–96)	8882 (72–92)	7478 (65–89)	0.0001
Tegner^b, nMedian (IQR)	2274 (3–5)	665 (4–6)	874 (2–5)	744 (3–5)	0.0054
K-SES^b, nMean (SD)	2197.0 (2.4)	638.3 (1.7)	846.5 (2.4)	726.3 (2.5)	0.0001
PASS^d, nYes (%)	215110 (51.2)	6139 (63.9)	8439 (46.4)	7032 (45.7)	0.062

a Score from 0 to 100 with higher scores indicate less symptoms.

b Score from 0 to 10 with higher score indicating higher work and sport activity level.

As presented in Fig. 2, the SAQ showed that the number of participants engaged in high-impact sports in the primary group decreased by 11 (31 %), low-impact participation increased by 5 (50 %), and no sport participation increased by 6 (35 %). In the recurrent group, the number of participants engaged in high-impact sports decreased by 29 (59 %), low-impact participation decreased by 5 (29 %), and no sport participation increased by 34 (189 %). In the surgery group, the number of participants engaged in high-impact sports decreased by 25 (58 %), low-impact participation increased by 2 (18 %), and no sport participation increased by 23 (144 %). Statistical analysis showed that high-, low-, and no-sport participation changes from pre-to post-injury were not statistically significant in the primary dislocation group (χ²(2) = 3.88, p = 0.143). In contrast, significant differences were found in both the recurrent dislocation group (χ²(2) = 29.56, p < 0.001) and the surgery group (χ²(2) = 20.03, p < 0.001). The proportion of participants who responded that their decrease in sports participation was related to their knee injury in the primary, recurrent, and surgery groups was 35 %, 58 %, and 74 %, respectively.

Changes in the three categories of sporting and recreational activities (high-impact, low-impact, and no sport) from pre-to post-injury.

The median Tegner score was 4 (IQR: 3–5) for the overall group, 5 (IQR: 4–6) for the primary group, 4 (IQR: 2–5) for the recurrent group, and 4 (IQR: 3–5) for the surgery group. Participants who were satisfied with their current knee function (PASS) were 51.2 % overall, 63.9 % for the primary group, 46.4 % for the recurrent group, and 45.7 % for the surgery group. Their mean (SD) knee self-efficacy was 8.3 (1.7) in the primary group, 6.5 (1.7) in the recurrent group, and 6.3 (2.5) in the surgery group. Results from the statistical analysis for differences between groups in these secondary outcomes are presented in Table 2.

4 Discussion

To our knowledge, this is the first study to assess clinical outcomes and participation in sporting and recreational activities in patients with prior patellar dislocation, including both surgical and conservative treatments. At a median follow-up of 2–3 years, recovery appears inadequate, with a median Kujala score of 84 (IQR: 70–93), and approximately half of participants report dissatisfaction with their current knee function via PASS. The SAQ shows a decrease in high-impact sports participation and an increase in the proportion of participants reporting no sport from pre-injury to post-injury.

4.1

4.1 Clinical outcome, sporting and recreational activities

Our results showed a median Kujala score of 89 (IQR: 78–96) in the primary and 82 (IQR: 72–92) in the recurrent groups. These results align with the Cochrane review, where the non-surgical group scored a mean of 82 after 2–9 years.⁸ Additionally, a systematic review found that patients reach only 80 % of the maximum score across clinical outcome measures after non-operative treatment.³² The review concluded that although clinical outcomes improve, function does not return to pre-injury levels. Our results indicated that the surgery group scored significantly lower on the Kujala score than the primary dislocation group. Due to the observational design, we cannot conclude on the effectiveness of surgery, since lower post-surgery Kujala scores may reflect greater preoperative severity.

Our findings suggest that patellar dislocations may cause long-term reductions in physical function, contributing to a shift from high-to low-impact or cessation of sports activities. A meta-analysis of longitudinal studies has shown an age-related decline in physical activity from adolescence to adulthood,³³ which may partly explain our findings. Nevertheless, Aira et al. emphasized the role of sports club participation in preventing such declines.³⁴ Our results show decreased participation in team sports such as football and handball (Fig. 3) and a shift away from high-impact activities (Fig. 2). This change in sport participation is reflected in a median Tegner score of 4 (IQR: 3–5), compared to 6.5 in uninjured 18–30-year-olds.³⁵ According to a systematic review on return to sport after patella stabilization surgery, the reasons for reducing the level of play were most commonly fear of reinjury, followed by loss of function.³⁶

Sport-specific changes following patellar dislocation. Describes the number of participants engaging in sporting activities regularly prior and 6 months post injury.

4.2

4.2 Strengths and limitations

The strengths of this study are: 1) the large number of participants, which is among the most extensive studies to date, thereby enhancing the external validity, and 2) the participants were both surgical and non-surgical individuals, different from previous studies. This improves generalizability by representing a wide range of patients, from patients with single to multiple dislocations and surgical cases, and offers insight into clinical outcomes across treatment types. While direct comparisons between surgical and non-surgical treatments are not possible, the results suggest that surgery is insufficient to restore patients to full physical function.

A limitation of self-reported retrospective studies is recall bias, which may affect the response accuracy of some outcomes.³⁷ A 49.5 % response rate introduces potential non-response bias. Nonetheless, our response rate is comparable to that reported among men aged 16–35 in a Danish National Health Survey,³⁸ and higher than the 29.8 % reported by Magnusson et al.¹⁴ Non-responders often have lower sociodemographic status,³⁸^,³⁹ a risk factor for musculoskeletal pain.⁴⁰ However, age and sex were similar between responders and non-responders, with 35 % male and a mean age of 27 years. Another limitation is the unknown prevalence of osteochondral injuries, commonly seen following patellar dislocation,²^,⁴¹ and a risk factor for poorer clinical outcomes.⁴² Even a single dislocation can initiate cartilage deterioration and lead to patellofemoral osteoarthritis.⁴³ However, a thorough assessment of osteochondral lesions requires MRI, which was not routinely performed in this population.

4.3

4.3 Clinical implications and future perspectives

The overall PASS score shows that 48.8 % are unsatisfied with their current knee function, suggesting a need for changes in treatment to improve patient satisfaction. K-SES scores were lower in recurrent dislocation, and surgery did not appear to improve self-efficacy sufficiently. This may be an important factor, as studies on other knee injuries show that higher self-efficacy predicts lower pain, higher levels of physical activity, and higher return-to-sport rates.⁴⁴^,⁴⁵ Most studies examining associations between clinical outcomes and relevant factors are retrospective and inherently subject to various biases, so future prospective studies are needed. Moreover, studies should investigate risk factors for patellar dislocation, such as trochlear dysplasia and TT-TG distance,⁶ and their association with clinical outcomes.

5 Conclusion

Patellar dislocations may cause long-term physical limitations and reduced sports participation, with about half of patients dissatisfied with knee function at 2–3 years’ follow-up. surgical treatment does not appear sufficient to restore full function. These findings underscore the need for further research to improve treatment and rehabilitation.

Ethical statement

Written informed consent was obtained from all individual participants included in the study. The study was exempt from ethical approval under Danish law (Committee Law Section 14(1), cf. Section 2(1)). Approved by the Danish Data Protection Agency (J. nr. K2024-074).

Credit author statement

Jesper Lykkegård Toustrup: Conceptualization, Methodology, Investigation, Formal analysis, Writing- Original draft preparation, Writing- Reviewing and Editing.

Niklas Diget: Conceptualization, Methodology, Investigation, Writing- Original draft preparation.

Bogi Sørensen: Conceptualization, Methodology, Investigation, Writing- Original draft preparation.

Henrik Riel: Methodology, Formal analysis Writing- Reviewing and Editing.

Carsten Møller Mølgaard: Conceptualization, Methodology, Writing- Reviewing and Editing.

Declaration of generative AI and AI-assisted technologies in the writing process

During the preparation of this work, the authors used ChatGPT in order to improve readability, spelling, and grammar checking. After using this tool, the authors reviewed and edited the content as needed and take full responsibility for the publication's content.

Funding statement

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

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Show Sections

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Back on track, but still benched: Long-term impact of patellar dislocation on sport and function – A retrospective cohort study

Abstract