Anterior knee laxity in young women varies with their menstrual cycle

We studied 16 women 21-23 years old with regular menstrual cycles (28+/-4 days) and no history of knee injury. From their basal body temperatures and the serum concentrations of estradiol and progesterone, the follicular, ovulatory, and luteal phases were delineated. Using a KT-2000 arthrometer, anterior displacement at 89 N and 134 N and anterior terminal stiffness (N/mm) at 134 N were measured two or three times every week over a 4-week period. Eight men 21-23 years old were also measured. In women the anterior displacement at 89 N varied between the follicular and the ovulatory phase and between the follicular and the luteal phase ( P<0.05) and at 134 N between the follicular and the luteal phase ( P<0.05). There were no statistical differences in the anterior displacement with time in men, nor in anterior terminal stiffness in either sex. We conclude that anterior cruciate ligament laxity in women might be dependent on the concentrations of hormones.     

Inherent laxity in total knee prostheses

The anterior-posterior and rotatory laxities of 14 total knee prosthesis designs were measured in a loading rig with compressive, shear, and torque loads representative of physiologic loads. The measured laxities covered a wide range, both greater and smaller than that of the anatomic knee. This range was mainly due to the curvature or flatness of the plastic tibial surface and conformity with the femoral component. Pressure patterns showed the corresponding contact track and area on the tibial surfaces. It is proposed that for normal function, the laxity of the device should complement the remaining anatomic structures to produce a combined laxity resembling that of the normal knee. Excessive prosthetic laxity will lead to the risk of instability, soft tissue attenuation, edge-loading on components, and high contact stresses on the plastic. Inadequate prosthetic laxity may lead to altered kinematics and excessive stresses at the interface, running the risk of long-term loosening. The authors show the laxities of many currently used devices, providing important background information for assessing the role intrinsic prosthetic constraint might play in total joint performance in clinical analyses.     

Combination auto-heteroplasty in ligament repair in chronic anterior laxity of the knee]

From September 85 to September 88, 130 patients were treated by our own technique for chronic laxity of the knee. All the patients were examined at regular intervals (6, 12 and 24 months) both clinically and by arthroscopy. Neuromorphological studies, an experimental approach with the "Pivot" and evaluation of the results, show that surgery is indicated, especially in young patients, before intraarticular lesions appear.     

Objective evaluation of knee laxity in children

This study was designed to measure objectively knee laxity in children. Physical examination and the KT 1000 arthrometer were used to test the knee laxity of 150 healthy, uninjured children between 6 and 18 years of age. Data from the knee examinations and the KT 1000 measurements were compared and statistically analyzed to determine the change in knee laxity with age, laxity differences between boys and girls, and the correlation between the KT1000 measurements and subjective tests for laxity described by Carter and Wilkinson. There was no statistical difference in knee laxity between boys and girls of similar ages. We found that knee laxity, determined by measuring the millimeters of tibial translation using the KT 1000 arthrometer, was significantly greater in younger children.     

Influence of collateral ligament laxity on patient satisfaction after total knee arthroplasty: a comparative bilateral study

Introduction Correct ligamentous balancing is an important determinant of the clinical outcome in total knee arthroplasty (TKA). Many surgeons prefer a tight rather than a lax knee during implantation of a TKA. The hypothesis in this study was that patients with a slightly laxer knee joint might perform better than patients with a tight knee joint after implantation of a TKA.Patients and methods Twenty-two patients with bilateral knee arthroplasties were clinically and radiologically evaluated at a mean follow-up of 4.5 years, ranging from 2 to 7 years. There were 12 women and 10 men with an average age of 68.9 years (range 32–82 years) at the time of surgery. A modified HSS score (excluding laxity), varus and valgus stress X-rays in 30° of knee flexion, and the subjective outcome of both knees were compared. A knee was considered tight when it opened less than 4° and lax if it opened 4° or more on stress X-ray.Results There was a trend towards improved range of motion and HSS score for the laxer knee joints. However, the difference did not achieve statistical significance. Eleven of the 22 patients considered one side subjectively better than the other side. In 10 out of these 11 TKA, the slacker knee joint was the preferred side (p<0.05).Conclusions As the present study compared bilateral knee joints after TKA, the same patient could act as a control group, and subtle subjective differences were revealed which are not quantifiable. The results showed that patients with a preferred side felt significantly more comfortable on the laxer side, indicating that during intraoperative ligamentous tensioning, some varus and valgus laxity at 20–30° of flexion might be preferable to an over-tight knee joint. Further biomechanical and prospective investigations will be necessary to establish the correct soft-tissue tensioning.     

Sagittal plane laxity following knee arthroplasty

We measured the sagittal laxity in 70 knee replacements at least six months after surgery, using a KT 1000 arthrometer. With an unconstrained prosthesis (the Oxford meniscal knee) anteroposterior stability was normal in joints known to have intact cruciate ligaments. There was increased laxity in those which lacked an anterior cruciate ligament. In knees with an intact anterior cruciate ligament, sagittal laxity did not increase with time.     

Sagittal laxity in vivo after total knee arthroplasty

Introduction A stress arthrometry study of 77 knees undergoing total knee arthroplasty was performed to determine the difference in anteroposterior (AP) laxity between posterior cruciate ligament (PCL)-retaining (PCLR) and PCL-substituting (PCLS) prostheses using the Genesis I TKA.Materials and methods Fifty-three knees had PCLR and 24 had PCLS prostheses. The selected patients had successful arthroplasties after a minimum follow-up of 5 years. AP laxity was measured with a KT-2000 arthrometer (Medmetric, San Diego, CA, USA) using standard protocols.Results At 30° of flexion, there was no statistical difference in anterior (PCLR: 4.7 mm, PCLS: 4.5 mm), posterior (PCLR: 1.1 mm, PCLS: 0.7 mm), or total (PCLR: 5.8 mm, PCLS: 5.3 mm) displacement. At 75°, significant differences were seen in both anterior (PCLR: 3.3 mm, PCLS: 2.3 mm) and total (PCLR: 4.8 mm, PCLS: 3.4 mm) displacement (p=0.001 and p=0.009, respectively), although there was no statistical difference in posterior displacement (PCLR: 1.5 mm, PCLS: 1.1 mm).Conclusion The above values are considered the suitable degree of AP laxity in total knee arthroplasty for a satisfactory clinical outcome 5–9 years after surgery. The PCL in a PCLR prosthesis and the central tibial spine and femoral cam in a PCLS prosthesis might play comparable roles in determining the laxity in the posterior direction in these prostheses.     

Rotational laxity and collateral ligament laxity following total knee arthroplasty with rotating platform

Purpose

The aim of this study was to evaluate laxity in knees with pre-operative (preop) valgus alignment compared to knees with pre-operative varus alignment after total knee arthroplasty (TKA).

Methods

This was a retrospective study including 81 patients, with six years follow-up, for pre-operative valgus- or varus alignment of the leg. All patients had been supplied with the same cruciate retaining (CR) TKA with rotating platform. Clinical findings were assessed by KSS, OKS and IKDC 2000 score. Rotational knee laxity was evaluated by a validated instrument (Laxitester®) with 2 Nm torque in 30° flexion. Collateral ligament laxity was tested manually in 30° flexion with a bending moment of approximately 5 Nm. Biomechanical results were compared to the contralateral side.

Results

Thirty-one patients had a preop valgus alignment of 8.96° and 50 patients a varus leg axis of 4.99° in the mean. In the preop valgus knees rotational analysis showed an increased laxity of 10.7° compared to preop varus knees (p = 0.001). There was no significant difference in medial (valgus 2.6 mm, varus 2.5 mm) and lateral (valgus 2.8 mm, varus 2.7 mm) laxity. KSS and OKS showed no significant differences in the follow-up results. In the IKDC 2000 objective score 50 % of the preop varus knees and 25.8 % of the preop valgus knees were classified as nearly normal. The difference in the IKDC objective was highly significant (p < 0.001).

Conclusion

Preop valgus knees show a significantly increased rotational laxity but no increased collateral ligament laxity compared to pre-operative varus knees six years after TKA with rotating platform. There is a significant difference in IKDC objective.     

Preoperative laxity in osteoarthritis patients undergoing total knee arthroplasty

A preoperative quantitative evaluation of soft tissues is helpful for planning total knee arthroplasty, in addition to the conventional clinical examinations involved in moving the knee manually. We evaluated preoperative coronal laxity with osteoarthritis in patients undergoing total knee arthroplasty by applying a force of 150 N with an arthrometer. We examined a consecutive series of 120 knees in 102 patients. The median laxity was 0° in abduction and 8° in adduction. The femorotibial angle on non-weight-bearing standard anteroposterior radiographs was 180° and correlated with both abduction (r = −0.244, p = 0.007) and adduction (r = 0.205, p = 0.025) laxity. The results of a regression analysis suggested that the femorotibial angle is helpful for estimating both laxities. Considering the many reports on how to obtain well-balanced soft tissues, stress radiographs might help to improve the preoperative planning for gaining the optimal laxity deemed appropriate by surgeons.

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Résumé  Une analyse avec évaluation quantitative préopératoire des tissus mous est nécessaire dans la planification d’une prothèse totale de genou, ceci en plus des examens cliniques conventionnels, notamment en ce qui concerne l’évaluation de la mobilité. Nous avons évalué, en préopératoire, les laxités ainsi que les stades de l’arthrose chez les patients qui ont bénéficié d’une prothèse totale du genou. Ces résultats ont été réalisés à l’arthromètre. Nous avons réalisé une série consécutive de 120 genoux chez 102 patients. La laxité moyenne était de 0° en abduction et de 8° en adduction. L’angle fémoro tibial, sans appui, sur les radiographies de face et de profil était de 180° et a été corrélé avec la laxité en abduction (r = −0.244, p = 0.007) et en adduction (r = 0.205, p = 0.025). Les résultats nous montrent que l’angle fémoro tibial est utile pour estimer les laxités. Si l’on considère les différentes études et la meilleure manière d’obtenir une bonne balance ligamentaire, les radiographies en stress permettent d’optimiser le planning opératoire et d’avoir une bonne idée des laxités.

     

Relationship between outcome scores and knee laxity following total knee arthroplasty: a systematic review

Background and purpose — Instability following primary total knee arthroplasty (TKA) is, according to all national registries, one of the major failure mechanisms leading to revision surgery. However, the range of soft-tissue laxity that favors both pain relief and optimal knee function following TKA remains unclear. We reviewed current evidence on the relationship between instrumented knee laxity measured postoperatively and outcome scores following primary TKA.

Patients and methods — We conducted a systematic search of PubMed, Embase, and Cochrane databases to identify relevant studies, which were cross-referenced using Web of Science.

Results — 14 eligible studies were identified; all were methodologically similar. Both sagittal and coronal laxity measurement were reported; 6 studies reported on measurement in both extension and flexion. In knee extension from 0° to 30° none of 11 studies could establish statistically significant association between laxity and outcome scores. In flexion from 60° to 90° 6 of 9 studies found statistically significant association. Favorable results were reported for posterior cruciate retaining (CR) knees with sagittal laxity between 5 and 10?mm at 75–80° and for knees with medial coronal laxity below 4° in 80–90° of flexion.

Interpretation — In order to improve outcome following TKA careful measuring and adjusting of ligament laxity intraoperatively seems important. Future studies using newer outcome scores supplemented by performance-based scores may complement current evidence.     

Shoulder instability Assessment of anterior-posterior translation with a knee laxity tester

We developed a simple method to measure the anterior-posterior (AP) translation of the shoulder joint: by positioning the Donjoy® Knee Laxity Tester horizontally over the shoulder girdle, the AP translation was measured after applying a standardized sagittal force.

Measurement of AP-translation during two tests on the same shoulder was reproducible with an intraclass correlation coefficient (ICC) of 0.996.

In normal subjects the mean side difference was 0.6 mm, corresponding to a p-value of 1.00. In patients with unilateral instability AP-translation was significantly larger on the injured shoulder. Furthermore, the intraindividual differences in AP-translation were significantly larger in patients with unilateral instability than in normal subjects. Individuals with multidirectional instability had significantly higher values than any of the other groups.     

Anterior knee pain in females

There are clear differences between men and women regarding anterior knee pain. Anatomic factors including increased pelvic width and resulting excessive lateral thrust on the patella are primary factors that predispose females to anterior knee pain. Effects of estrogen on connective tissue synthesis have been reported, but there is no clear mechanism by which this would affect anterior knee pain. Postural and sociologic factors such as wearing high heels and sitting with legs adducted can influence the incidence and severity of anterior knee pain in women.     

Instrumented testing for evaluation of sagittal knee laxity

Seventy-one patients with untreated ruptures of the anterior cruciate ligament of at least four years' duration had their knee laxity examined with a laxity testing device. Twenty of the 71 patients were tested by two examiners independently. Another 30 patients without previous knee injury were chosen as a reference group and tested. Patients with anterior cruciate-deficient knees had significantly increased anterior and total laxity. If the testing procedure was altered, the laxity changed. Thus, an increase of knee flexion from 15 degrees to 25 degrees resulted in an increased anterior laxity. Changes in the amount and placement of the tibial load also affected laxity. Inter-examiner reproducibility was high if a standardized testing procedure was followed. Sensitivity was 92% if the difference in total laxity between involved and uninvolved knees was determined with a high tibial load (180 N), whereas specificity was 70%. Therefore, the laxity tester has disadvantages as a diagnostic tool, but it is still valuable for evaluation of anterior cruciate ligament ruptures and their treatment.     

Body type and rotational laxity of the knee

Forty young adult males were somatotyped according to the Health-Carter Modified Method and were separated into 2 groups. One group was a meso-endomorphic body type (5-6-1) and the other was ectomorphic body type (3-2-4). Measurement of rotational laxity of the knee in 90 degrees flexion showed a statistically significant increase (p less than .001) in external rotation and total rotation in ectomorphs compared to meso-endomorphs. Rotational laxity of the knee is associated with body type. Lateral radiographs were used to measure patellae alta in each group. No statistical difference was found, and patellae alta does not appear to be associated with body type.     

Coronal laxity in extension in vivo after total knee arthroplasty

We performed stress arthrometric studies on 77 knees (71 patients) with total knee arthroplasty to determine the presence and magnitude of femoral abduction and adduction in knee extension. A total of 53 knees (49 patients) had posterior cruciate ligament-retaining (PCLR) prostheses, and 24 (22 patients) had PCL-substituting (PCLS) prostheses. The selected patients had successful arthroplasties with no clinical complications a minimum of 5 years after primary surgery. Each patient was subjected to a successive abduction and adduction stress test at 0°–20° of flexion using a Telos arthrometer. The mean values for abduction and adduction were 4.8° and 4.5° with a PCLR prosthesis, respectively, and 4.6° and 4.0° with a PCLS prosthesis. There were no statistical differences between PCLR and PCLS knees. The results suggest that approximately 4° of laxity in these directions is suitable in total knee arthroplasty for a satisfactory clinical outcome 5–9 years after surgery.     

Changes in ligamentous laxity after posterior stabilized total knee replacement and factors correlated with postoperative laxity

Instruction

Total knee arthroplasty (TKA) performed with the gap technique can achieve rectangular gaps during flexion and extension by proper bone resection and subsequent soft tissue release. Acquisition of appropriate soft tissue balance is important for successful TKA. It is unknown, however, whether the intraoperative well-balanced ligamentous laxity changes postoperatively over time. We hypothesized that even if good soft tissue balance was achieved intraoperatively the lateral ligamentous laxity would increase with time postoperatively. This phenomenon depends on preoperative background factors.

Methods

We used the angle between the component surfaces of the tibia and femur to define ligamentous laxity. Changes in ligamentous laxity after posterior stabilized minimally invasive surgery (MIS)-TKA were analyzed retrospectively in 150 knees based on radiographic measurements. At 12 months after the operation, the cases were divided into two groups in which the lateral ligamentous laxity in flexion was either ≤3° (balanced group) or >3° (unbalanced group). Factors with a potential to encourage postoperative ligamentous laxity were analyzed.

Results

Our data show that the postoperative ligamentous laxity in extension did not change, whereas the lateral ligamentous laxity in flexion increased with time. This change was significantly related to the preoperative lateral ligamentous laxity, body weight, body mass index, and age.

Conclusion

The results of this study should be taken into account by surgeons performing MIS-TKA with the gap technique.     

Anterior knee pain after total knee arthroplasty: a narrative review

Anterior knee pain is one of the most common causes of persistent problems after implantation of a total knee replacement. It can occur in patients with or without patellar resurfacing. As a result of the surgical procedure itself many changes can occur which may affect the delicate interplay of the joint partners in the patello-femoral joint. Functional causes of anterior knee pain can be distinguished from mechanical causes. The functional causes concern disorders of inter- and intramuscular coordination, which can be attributed to preoperative osteoarthritis. Research about anterior knee pain has shown that not only the thigh muscles but also the hip and trunk stabilising muscles may be responsible for the development of a dynamic valgus malalignment. Dynamic valgus may be a causative factor for patellar maltracking. The mechanical causes of patello-femoral problems after knee replacement can be distinguished according to whether they increase instability in the joint, increase joint pressure or whether they affect the muscular lever arms. These causes include offset errors, oversizing, rotational errors of femoral or tibial component, instability, maltracking and chondrolysis, patella baja and aseptic loosening. In these cases, reoperation or revision is often necessary.