RESUMEN
OBJECTIVES: To study bone shape changes as a potential early feature of post-traumatic structural knee OA development, we estimated the association between meniscal status in the anterior cruciate ligament (ACL) injured knee and longitudinal condyle changes in bone surface area. DESIGN: We used data from the KANON trial, including 121 young ACL-injured adults. We obtained baseline and 2-year follow-up knee MRIs. Our outcome was change in the bone surface areas (mean mm2, log-transformed) in 4 locations (femur, tibia, patella, and trochlea femur) in the medial and lateral compartment from baseline to 2 years. Meniscal pathology was defined as both present at baseline and newly developed (i.e., incident or progressed) using ACLOAS. We used multilevel linear regression adjusted for baseline bone area, age, sex, body mass index, treatment arm (i.e., early or optional delayed ACL reconstruction), and location. We analyzed medial and lateral compartment separately. We present results as percentage (%) bone area change difference with 95% confidence intervals (CI). RESULTS: We analyzed 109 subjects (median 27 (18-36) years, 83% men) due to missing MRI information. The bone surface area increased on average by â¼2% over 2 years. The differences between knees with and without baseline meniscal pathology were 1.1% (95%CI 0.0-2.3%) and 1.4% (95%CI 0.6-2.2%) in the medial and lateral compartment, respectively, and 1.2% (95%CI 0.3-2.0%) and 1.3% (95%CI 0.6-2.0%) for medial and lateral newly developed pathology, respectively. CONCLUSION: Our finding of â¼1% increase bone area in compartment with meniscal pathology suggests a potentially important association between meniscal integrity and early bone surface area changes after ACL injury. Trial registration number ISRCTN 84752559.
Asunto(s)
Lesiones del Ligamento Cruzado Anterior/patología , Meniscos Tibiales/patología , Adolescente , Adulto , Femenino , Humanos , Masculino , Estudios Prospectivos , Adulto JovenRESUMEN
OBJECTIVE: To compare 5-year change in femorotibial cartilage thickness in 121 young, active adults with an acute anterior cruciate ligament (ACL) tear randomized to a strategy of structured rehabilitation plus early ACL reconstruction (ACLR) or structured rehabilitation plus optional delayed ACLR. DESIGN: 62 patients were randomized to early ACLR, 59 to optional delayed ACLR. Magnetic resonance imaging (MRI) was acquired within 4 weeks of injury, at two- and 5-years follow-up. Main outcome was 5-year change in overall femorotibial cartilage thickness. Secondary outcomes included the location-independent cartilage ChangeScore, summarizing thinning and thickening in 16 femorotibial subregions. An exploratory as-treated comparison was performed additionally. RESULTS: Baseline and at least one follow-up MRI were available for 117 patients. Over 5 years, a comparable increase in overall femorotibial cartilage thickness was observed for patients randomized to early ACLR (n = 59) and patients randomized to optional delayed ACLR (n = 58, adjusted mean difference: -5 µm, 95% CI: [-118, 108]µm). However, the location-independent cartilage ChangeScore was greater in those treated with early ACLR than in patients treated with optional delayed ACLR (adjusted mean difference: 403 µm [119, 687]µm). As-treated analysis showed no between-group differences for the main outcome, while the location-independent cartilage ChangeScore was greater for patients treated with early (adjusted mean difference: 632 µm [268, 996]µm) or delayed ACLR (adjusted mean difference: 449 µm [108, 791]µm) than for patients treated with rehabilitation alone. CONCLUSIONS: In young active adults with acute ACL-injury, choice of treatment strategy for the injured ACL did not modify the magnitude of 5-year change in overall femorotibial cartilage thickness. TRIAL REGISTRATION: ISRCTN84752559.
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Lesiones del Ligamento Cruzado Anterior/cirugía , Reconstrucción del Ligamento Cruzado Anterior/métodos , Cartílago Articular/diagnóstico por imagen , Articulación de la Rodilla/diagnóstico por imagen , Adolescente , Adulto , Lesiones del Ligamento Cruzado Anterior/rehabilitación , Cartílago Articular/patología , Femenino , Humanos , Articulación de la Rodilla/patología , Imagen por Resonancia Magnética , Masculino , Tamaño de los Órganos , Modalidades de Fisioterapia , Factores de Tiempo , Adulto JovenRESUMEN
BACKGROUND: To investigate changes in knee 3D bone shape over the first 5 years after acute anterior cruciate ligament (ACL) injury in participants of the randomized controlled KANON-trial. METHODS: Serial MR images over 5 years from 121 young (32 women, mean age 26.1 years) adults with an acute ACL tear in a previously un-injured knee were analyzed using statistical shape models for bone. A matched reference cohort of 176 individuals was selected from the Osteoarthritis Initiative (OAI). Primary endpoint was change in bone area of the medial femoral condyle; exploratory analyses compared results by treatment and examined other knee regions. Comparisons were made using repeated measures mixed model ANOVA with adjustment for age, sex and body mass index (BMI). RESULTS: Mean medial femur bone area increased 3.2% (78.0 [95% CI 70.2 to 86.4] mm2) over 5 years after ACL injury and most prominently in knees treated with ACL reconstruction (ACLR). A higher rate of increase occurred over the first 2 years compared to the latter 3-years (66.2 [59.3 to 73.2] vs 17.6 [12.2 to 23.0] mm2) and was 6.7 times faster than in the reference cohort. The pattern and location of shape change in the extrapolated KANON data was very similar to that observed in another knee-osteoarthritis cohort. CONCLUSION: 3D shape modelling after acute ACL injury revealed rapid bone shape changes, already evident at 3 months. The bone-change pattern after ACL injury demonstrated flattening and bone growth on the outer margins of the condyles similar to that reported in established knee osteoarthritis.
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Lesiones del Ligamento Cruzado Anterior/diagnóstico , Reconstrucción del Ligamento Cruzado Anterior/métodos , Cartílago Articular/patología , Fémur/patología , Articulación de la Rodilla/diagnóstico por imagen , Osteoartritis de la Rodilla/etiología , Enfermedad Aguda , Adulto , Lesiones del Ligamento Cruzado Anterior/complicaciones , Lesiones del Ligamento Cruzado Anterior/cirugía , Femenino , Humanos , Imagen por Resonancia Magnética/métodos , Masculino , Persona de Mediana Edad , Osteoartritis de la Rodilla/diagnósticoRESUMEN
OBJECTIVE: In patients with traumatic knee distorsion and hemarthrosis, to investigate the panorama of structural injury, as visualized on magnetic resonance imaging (MRI). DESIGN: Cohort study of 1145 consecutive patients with traumatic knee distorsion who underwent MRI within median 8 days after injury. We present structural injury as visualized on MRI in relation to age, sex and activity at injury. Population based gender specific annual incidences of common structural injuries were calculated. RESULTS: The majority of injuries (72%) occurred during sports. Overall, anterior cruciate ligament (ACL) rupture was the most common structural injury (52%), followed by meniscal tear (41%) and lateral patella dislocation (LPD, 17%). Only 12% of ACL tears were isolated with meniscal tear being the most common associated injury (55%). The annual incidence of ACL injury was 77 (70-85, 95% CI) per 100,000 inhabitants with significant differences between men (91, 80-103) and women (63, 53-73). In those aged 16 years and younger, LPD was the most frequent structural injury, both in boys (39%) and girls (43%). In this age group, the annual incidence of LPD was 88 (68-113) and higher in boys (113, 81-154) than in girls (62, 39-95). CONCLUSIONS: ACL injury occurs in one out of two knees with traumatic hemarthrosis but only 12% are without concomitant structural injury. The overall rate of traumatic knee hemarthrosis and ACL injury is higher in men. In those aged 10-19 years, ACL rupture is more common among girls than boys whereas in those 16 years and younger, LPD is more common among boys than girls.
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Hemartrosis , Estudios de Cohortes , Femenino , Humanos , Traumatismos de la Rodilla , Articulación de la Rodilla , Imagen por Resonancia Magnética , MasculinoRESUMEN
OBJECTIVE: Anterior cruciate ligament (ACL) rupture involves an increased risk of osteoarthritis. The purpose of this study was to explore changes in cartilage thickness over 5 years after ACL rupture. METHODS: A total of 121 young active adults (ages 18-35 years; 26% women) from the Knee ACL, Nonsurgical versus Surgical Treatment (KANON) study, who had acute traumatic rupture of the ACL were studied. Sagittal magnetic resonance images were acquired within 4 weeks of ACL rupture (baseline) and at the 2-year and 5-year followup assessments. Medial and lateral femorotibial cartilage was segmented (with blinding to acquisition order), and the mean cartilage thickness was computed across 16 femorotibial subregions. Total femorotibial cartilage thickness change was the primary analytic focus. Maximal subregional mean cartilage thickness loss (ordered value 1 [OV1]) and gain (ordered value 16 [OV16]), independent of its specific location in individual knees, were the secondary analytic focus. RESULTS: Overall femorotibial cartilage thickness increased by 31 µm/year over 5 years (95% confidence interval 18, 44). The increase was similar in men and women and was significantly greater in those younger, as compared with those older, than the median age (25.3 years). The rate of total cartilage thickness change did not differ significantly between the first 2 years and the later 3 years. However, the maximal annualized subregional cartilage loss (OV1) and gain (OV16) were both significantly greater (P < 0.001 and P < 0.05, respectively) during the earlier interval than during the later interval (-115 versus -54 µm [OV1] and 116 versus 69 µm [OV16]). CONCLUSION: Cartilage thickening was observed over 5 years following ACL injury, particularly in the medial femorotibial compartment and in younger subjects. Major perturbations in cartilage homeostasis were seen over the first 2 years after ACL rupture, with simultaneous subregional thinning and thickening occurring within the same cartilage plate or compartment.
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Lesiones del Ligamento Cruzado Anterior , Ligamento Cruzado Anterior/patología , Cartílago Articular/patología , Articulación de la Rodilla/patología , Adolescente , Adulto , Estudios de Cohortes , Femenino , Estudios de Seguimiento , Humanos , Estudios Longitudinales , Imagen por Resonancia Magnética , Masculino , Osteoartritis de la Rodilla/epidemiología , Factores de Riesgo , Rotura/patología , Factores de Tiempo , Adulto JovenRESUMEN
Joint injury has been recognized as a potent risk factor for the onset of osteoarthritis. The vast majority of studies using imaging technology for longitudinal assessment of patients following joint injury have focused on the injured knee joint, specifically in patients with anterior cruciate ligament injury and meniscus tears where a high risk for rapid onset of post-traumatic osteoarthritis is well known. Although there are many imaging modalities under constant development, magnetic resonance (MR) imaging is the most important instrument for longitudinal monitoring after joint injury. MR imaging is sensitive for detecting early cartilage degeneration and can evaluate other joint structures including the menisci, bone marrow, tendons, and ligaments which can be sources of pain following acute injury. In this review, focusing on imaging following acute knee trauma, several studies were identified with promising short-term results of osseous and soft tissue changes after joint injury. However, studies connecting these promising short-term results to the development of osteoarthritis were limited which is likely due to the long follow-up periods needed to document the radiographic and clinical onset of the disease. Thus, it is recommended that additional high quality longitudinal studies with extended follow-up periods be performed to further investigate the long-term consequences of the early osseous and soft tissue changes identified on MR imaging after acute knee trauma.
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Lesiones del Ligamento Cruzado Anterior , Cartílago Articular/lesiones , Traumatismos de la Rodilla/diagnóstico , Articulación de la Rodilla/patología , Osteoartritis de la Rodilla/patología , Lesiones de Menisco Tibial , Adulto , Ligamento Cruzado Anterior/diagnóstico por imagen , Ligamento Cruzado Anterior/patología , Cartílago Articular/diagnóstico por imagen , Cartílago Articular/patología , Femenino , Humanos , Traumatismos de la Rodilla/diagnóstico por imagen , Traumatismos de la Rodilla/patología , Articulación de la Rodilla/diagnóstico por imagen , Estudios Longitudinales , Imagen por Resonancia Magnética , Masculino , Meniscos Tibiales/diagnóstico por imagen , Meniscos Tibiales/patología , Osteoartritis de la Rodilla/diagnóstico por imagen , Tomografía Computarizada por Rayos X , Adulto JovenRESUMEN
OBJECTIVE: Investigate the 5-year longitudinal changes in bone curvature after acute anterior cruciate ligament (ACL) injury, and identify predictors of such changes. METHODS: In the KANON-trial (ISRCTN 84752559), 111/121 young active adults with an acute ACL tear to a previously un-injured knee had serial 1.5 T MR images from baseline (within 5 weeks from injury) to 5 years after injury. Of these, 86 had ACL reconstruction (ACLR) performed early or delayed, 25 were treated with rehabilitation alone. Measures of articulating bone curvature were obtained from computer-assisted segmentation of MR images. Curvature (mm(-1)) was determined for femur, tibia, medial/lateral femur, trochlea, medial/lateral tibia. Age, sex, treatment, BMI, meniscal injury, osteochondral fracture on baseline MR images were tested for association. RESULTS: Over 5 years, curvature decreased in each region (P < 0.001) suggesting flattening of convex shapes and increased concavity of concave shapes. A higher BMI was associated with flattening of the femur (P = 0.03), trochlea (P = 0.007) and increasing concavity of the lateral tibia (LT) (P = 0.011). ACLR, compared to rehabilitation alone, was associated with flatter curvature in the femur (P < 0.001), medial femoral condyle (P = 0.006) and trochlea (P = 0.003). Any meniscal injury at baseline was associated with a more flattened curvature in the femur (P = 0.038), trochlea (P = 0.039), lateral femoral condyle (P = 0.034) and increasing concavity of the LT (P = 0.048). CONCLUSION: ACL injury is associated with significant changes in articulating bone curvature over a 5 year period. Higher BMI, baseline meniscal injury and undergoing ACL reconstruction (as distinct from undergoing rehabilitation alone) are all associated with flattening of the articulating bone.
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Lesiones del Ligamento Cruzado Anterior , Fémur/patología , Traumatismos de la Rodilla/complicaciones , Traumatismos de la Rodilla/terapia , Tibia/patología , Adolescente , Adulto , Ligamento Cruzado Anterior/patología , Reconstrucción del Ligamento Cruzado Anterior , Índice de Masa Corporal , Femenino , Humanos , Traumatismos de la Rodilla/patología , Estudios Longitudinales , Imagen por Resonancia Magnética , Masculino , Modalidades de Fisioterapia , Factores de Tiempo , Resultado del Tratamiento , Adulto JovenRESUMEN
OBJECTIVE: Conflicting associations between imaging biomarkers and pain in knee osteoarthritis (OA) have been reported. A relation between pain and denuded areas of subchondral bone (dABs) has been suggested and this study explores this relationship further by relating the presence, phenotype, location and size of dABs to different measures of knee pain. METHODS: 633 right knees from the Osteoarthritis Initiative (OAI) (250 men, age 61.7 ± 9.6 yrs, BMI 29.4 ± 4.7 kg/m(2)) were included. Manual segmentation of the femorotibial cartilage plates was performed on 3 T coronal fast low angle shot with water excitation (FLASHwe) images. dABs were defined as areas where the subchondral bone was uncovered by cartilage. The following measures of pain were used: weightbearing-, non-weightbearing-, moderate-to-severe-, infrequent- and frequent knee pain. RESULTS: Using pain measures from subjects without dABs as a reference, those with at least one dAB had a 1.64-fold higher prevalence ratio [PR, 95% confidence interval (CI) 1.24-2.18] to have frequent and 1.45-fold higher for moderate-to-severe knee pain (95% CI 1.13-1.85). Subjects with dABs in central subregions had a 1.53-fold increased prevalence of having weightbearing pain (95% CI 1.20-1.97), especially when the central subregion was moderately (>10%) denuded (PR 1.81, 95% CI 1.35-2.42). Individuals with cartilage-loss-type dABs had a slightly higher prevalence (PR 1.13, 95% CI 1.00-1.27) of having frequent knee pain compared to individuals with intra-chondral-osteophyte-type dABs. CONCLUSION: This study supports a positive relation between femorotibial dABs and knee pain, especially when the dABs are located centrally (i.e., in weightbearing regions) or when the respective central subregion is moderately denuded.
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Artralgia/patología , Articulación de la Rodilla/patología , Imagen por Resonancia Magnética , Osteoartritis de la Rodilla/epidemiología , Osteoartritis de la Rodilla/patología , Anciano , Cartílago/patología , Femenino , Fémur/patología , Humanos , Masculino , Persona de Mediana Edad , Osteofito/epidemiología , Osteofito/patología , Dimensión del Dolor , Fenotipo , Prevalencia , Índice de Severidad de la Enfermedad , Tibia/patologíaRESUMEN
OBJECTIVE: To assess the presence, location, type and size of denuded areas of subchondral bone (dAB) in the femorotibial joint, measured quantitatively with 3T MRI, in a large subset of OAI participants. METHODS: One knee of 633 subjects (250 men, 383 women, aged 61.7+/-9.6 y) were studied, spanning all radiographic osteoarthritis (OA) stages. dABs were determined quantitatively using segmentations of coronal FLASHwe images, representing areas where the subchondral bone was not covered by cartilage. Post hoc visual examination of segmented images determined whether dABs represented full thickness cartilage loss or internal osteophyte. RESULTS: 7% Of the knees were Kellgren & Lawrence (KL) grade 0, 6% grade 1, 41% grade 2, 41% grade 3, and 5% grade 4. 39% Of the participants (48% of the men and 33% of the women) displayed dABs; 61% of the dABs represented internal osteophytes. 1/47 Participants with KL grade 0 displayed 'any' dAB whereas 29/32 of the KL grade 4 knees were affected. Even as early as KL grade 1, 29% of the participants showed dABs. There were significant relationships of dAB with increasing KL grades (P<0.001) and with ipsi-compartimental JSN (P< or =0.001). Internal osteophytes were more frequent laterally (mainly posterior tibia and internal femur) whereas full thickness cartilage loss was more frequent medially (mainly external tibia and femur). CONCLUSIONS: dABs occur already at earliest stages of radiographic OA (KL grades 1 and 2) and become more common (and larger) with increasing disease severity. Almost all KL grade 4 knees exhibited dABs, with cartilage loss being more frequent than internal osteophytes.
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Cartílago Articular/patología , Articulación de la Rodilla/patología , Osteoartritis de la Rodilla/patología , Anciano , Estudios de Cohortes , Estudios Transversales , Femenino , Humanos , Articulación de la Rodilla/diagnóstico por imagen , Imagen por Resonancia Magnética , Masculino , Persona de Mediana Edad , Osteoartritis de la Rodilla/complicaciones , Osteoartritis de la Rodilla/diagnóstico por imagen , RadiografíaRESUMEN
OBJECTIVES: To investigate changes in the knee during the first year after acute rupture of the anterior cruciate ligament (ACL) of volumes of joint fluid (JF), bone marrow lesions (BMLs), and cartilage volume (VC), and cartilage thickness (ThCcAB) and cartilage surface area (AC). To identify factors associated with these changes. METHODS: Fifty-eight subjects (mean age 26 years, 16 women) with an ACL rupture to a previously un-injured knee were followed prospectively using a 1.5T MR imager at baseline (within 5 weeks from injury), 3 months, 6 months, and 1 year. Thirty-four subjects were treated with ACL reconstruction followed by a structured rehabilitation program and 24 subjects were treated with structured rehabilitation only. Morphometric data were acquired from computer-assisted segmentation of MR images. Morphometric cartilage change was reported as mean change divided by the standard deviation of change (standard response mean, SRM). RESULTS: JF and BML volumes gradually decreased over the first year, although BML persisted in 62% of the knees after 1 year. One year after the ACL injury, a reduction of VC, AC and ThCcAB (SRM -0.440 or greater) was found in the trochlea femur (TrF), while an increase of VC and ThCcAB was found in the central medial femur (cMF) (SRM greater than 0.477). ACL reconstruction was directly and significantly related to increased JF volume at 3 and 6 months (P<0.001), BML volume at 6 months (P=0.031), VC and ThCcAB in cMF (P<0.002) and decreased cartilage area in TrF (P=0.010) at 12 months. CONCLUSION: Following an acute ACL tear, cMF and TrF showed the greatest consistent changes of cartilage morphometry. An ACL reconstruction performed within a mean of 6 weeks from injury was associated with increased ThCcAB and VC in cMF and decreased AC in TrF, compared to knees treated without reconstruction. This may suggest a delayed structural restitution in ACL reconstructed knees.
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Lesiones del Ligamento Cruzado Anterior , Médula Ósea/patología , Cartílago Articular/patología , Traumatismos de la Rodilla/patología , Líquido Sinovial/metabolismo , Adulto , Ligamento Cruzado Anterior/cirugía , Artroscopía , Médula Ósea/lesiones , Femenino , Estudios de Seguimiento , Humanos , Traumatismos de la Rodilla/rehabilitación , Traumatismos de la Rodilla/cirugía , Imagen por Resonancia Magnética/métodos , Masculino , Factores de Riesgo , Rotura , Adulto JovenRESUMEN
The aim of this study is to investigate if self-reported activity level or knee functions are influenced by subject characteristics, level of competition and history of knee injury. Cross-Sectional study using questionnaires distributed at a personal visit. One hundred and eighty-eight (65 women) amateur football players in 10 football clubs from each division below national level participated in the study. Self-reported Tegner Activity Scale, and the Knee injury and Osteoarthritis Outcome Score (KOOS) are the main outcome measures. Older age, female gender and lower level of competition (football division) were independently associated with lower self-reported Tegner Activity Scale (P < 0.001). Subjects reporting history of knee injury had significantly worse KOOS scores (P < 0.001 for all subscales). In future studies, a clear description of how the Tegner Activity Scale was administered is recommended. We suggest that self-reported Tegner Activity Scale scores should be adjusted for age, gender and level of competition. In amateur football players, KOOS scores do not need adjustment for age and gender.
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Fútbol Americano/psicología , Traumatismos de la Rodilla/fisiopatología , Traumatismos de la Rodilla/psicología , Actividad Motora/fisiología , Recuperación de la Función/fisiología , Autoimagen , Adolescente , Adulto , Factores de Edad , Índice de Masa Corporal , Conducta Competitiva , Estudios Transversales , Femenino , Fútbol Americano/lesiones , Fútbol Americano/fisiología , Humanos , Masculino , Factores Sexuales , Adulto JovenRESUMEN
OBJECTIVES: To map by magnetic resonance imaging (MRI) and quantitative MRI (qMRI) concomitant fractures and meniscal injuries, and location and volume of traumatic bone marrow lesions (BMLs) in the acutely anterior cruciate ligament (ACL) injured knee. To relate BML location and volume to cortical depression fractures, meniscal injuries and patient characteristics. METHODS: One hundred and twenty-one subjects (26% women, mean age 26 years) with an ACL rupture to a previously un-injured knee were studied using a 1.5T MR imager within 3 weeks from trauma. Meniscal injuries and fractures were classified by type, size and location. BML location and volume were quantified using a multi-spectral image data set analyzed by computer software, edited by an expert radiologist. RESULTS: Fractures were found in 73 (60%) knees. In 67 (92%) of these knees at least one cortical depression fracture was found. Uni-compartmental meniscal tears were found in 44 (36%) subjects and bi-compartmental in 24 (20%). One hundred and nineteen (98%) knees had at least one BML, all but four (97%) located in the lateral compartment. Knees with a cortical depression fracture had larger BML volumes (P<0.001) than knees without a cortical depression fracture, but no associations were found between meniscal tears and BML volume or fractures. Older age at injury was associated with smaller BML volumes (P<0.01). CONCLUSION: A majority of the ACL injured knees had a cortical depression fracture, which was associated with larger BML volumes. This indicates strong compressive forces to the articular surface and cartilage at the time of injury, which may constitute an additional risk factor for later knee osteoarthritis development.
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Lesiones del Ligamento Cruzado Anterior , Médula Ósea/lesiones , Traumatismos de la Rodilla/diagnóstico , Enfermedad Aguda , Adulto , Traumatismos en Atletas/diagnóstico , Médula Ósea/patología , Femenino , Fracturas Óseas/diagnóstico , Fracturas Óseas/etiología , Humanos , Traumatismos de la Rodilla/etiología , Imagen por Resonancia Magnética/métodos , Masculino , Estrés Mecánico , Lesiones de Menisco TibialRESUMEN
OBJECTIVES: To determine the incidence of anterior cruciate ligament (ACL) injuries in the general population; the pathology associated with a knee sprain verified by magnetic resonance imaging (MRI); and the agreement between clinical findings and MRI. MATERIAL AND METHODS: Inclusion criterion was an acute rotational trauma to the knee associated with effusion. One hundred and fifty-nine consecutive patients, mean age 27 years and 36% women, were included after clinical assessment at the orthopedic emergency unit. Patients were referred to an MRI examination (1.0 or 1.5 T) performed within a median of 8 days of the initial visit. RESULTS: The annual incidence of MRI verified ACL injuries was 0.81/1000 inhabitants aged 10-64 years. Fifty-six percent (n=89) of those included had sustained an ACL injury of whom 38% had an associated medial meniscus tear. There was a poor agreement between initial clinical antero-posterior laxity and MRI verified presence of an ACL tear (kappa 0.281). Every second patellar dislocation was diagnosed as a ligament injury. CONCLUSION: Our findings indicate that the incidence of ACL injuries is higher than previously described. We also show that the first clinical examination after an acute knee trauma has a low diagnostic value. Further assessment with MRI improves the chances of a correct diagnosis of intraarticular pathology and is recommended in the early phase after a rotational knee trauma.