Keywords
anterior cruciate ligament - diagnosis - knee joint - range of motion, articular
Palavras-chave
amplitude de movimento articular - articulação do joelho - diagnóstico - ligamento
cruzado anterior
Introduction
Studies on the existence of a distinct, ligamentous structure at the knee anterolateral
aspect (ALL),[1]
[2] have once again sparked discussion on knee rotatory instability after an anterior
cruciate ligament (ACL) injury. In injured knees, instability is evident through tibial
anteriorization on the anteroposterior plane, along with enhanced knee internal rotation.
An important correlation between rotatory instability and anterolateral structures
injuries has become evident.[3] However, it is still not clear which structure bears the most important role. Historically,
knee surgeons have considered that tibial rotatory control is important to ensure
knee stability.[4]
To date, there is still no consensus on which procedure produces the best rotatory
control for ACL reconstruction, however.[5]
[6] Recent studies of systematic revisions have concluded that, in some cases, the combination
of intra- and extra-articular ACL reconstructions could improve rotatory instability.[7]
[8] Having a clinical sign that could improve the identification of the association
between ACL with ALL injuries would help identify which patients would benefit from
combined reconstruction.
This study aimed to determine the measurement of the knee internal rotation that could
clearly demonstrate the association between ACL and ALL. More specifically, this investigation
focused on the clinical assessment to aid surgeons in the diagnosis of these associated
lesions. Our hypothesis was that an associated injury of anterolateral structures
in an ACL-deficient knee could be clinically defined by the measurement of internal
rotation.
Materials and Methods
A total of 19 entire cadaveric specimens were chosen, comprising 38 knees with no
evidence of ligament, chondral, or meniscal injury, with a minimum range of motion
from 0 to 130 degrees. All cadavers were obtained from the local coroner's office,
in accordance with the protocol approved by the Ethics Committee, under the CAAE:
45087815.0.0000.5327. The mean donor age was 28.42-years-old (range 18–47). All specimens
were fresh, less than 18 hours from death, and none had been previously frozen.
Surgical Approach
A standardized protocol[9] for the ACL, iliotibial tract (ITT) and ALL of both knees was employed for dissection
of 38 knees, from 19 fresh cadavers. Before the experiment, an adequate dissection
of structures was performed, initiating the anatomical dissection through the removal
of skin from the anterior and anterolateral aspects of the knee, creating a large
rectangular window. The ITT was identified ([Fig. 1]), and medial parapatellar arthrotomy proceeded with quadriceps tendon release to
expose the intercondylar region and the ACL. The bias produced by cadaveric rigidity
was avoided, since not all specimens had the same post mortem time.
Fig. 1 View of the lateral aspect of the right knee after removing the skin on the anterior
and anterolateral surfaces of the knee, creating a large rectangular window. The Iliotibial
tract (ITT) was then identified. Abbreviations: GT, Gerdy's tubercle; FH, fibular head.
The lower limb was positioned with the hip flexed at 45 degrees, the knee flexed at
90 degrees, and the foot flat on the table. After performing medial parapatellar arthrotomy
to identify the femoral intercondylar region and structures of interest, before the
experiment was started, all specimens were assessed to identify any injuries present.
Next, with the knees positioned in 90 degrees of flexion, two parallel 2.0 Kirschner
wires (K-wires) were inserted, one on the femoral intercondylar roof and the other
into the anterior tibial tuberosity.
A lateral extension of the approach was performed, initiating over Gerdy's tubercle
and extending proximally onto the thigh by 30 cm. A sequential release of the ACL
and knee anterolateral structures was then performed, starting at the ITT and moving
to the ALL, as determined in the experiment ([Fig. 2]).
Fig. 2 View of the lateral aspect of the right knee, the iliotibial tract (ITT) is dissected
and reflected anteriorly to expose the anterolateral ligament (ALL). This way, we
can access the ALL so we can identify it and then section it during the experiment.
Abbreviations: FH, fibular head; BT, biceps tendon.
Experiment
A goniometer was employed to obtain kinematic data, measuring the angle formed between
the two previously positioned K-wires. At the beginning of the experiment, before
performing ligament release, we determined the maximum internal rotation of the tibia
in relation to the fixed femur at 90 degrees of flexion. A STC-02 dynamometer (Mundial
Comercio de Presentes Ltda.) was used to obtain a strength pattern during rotation.
We applied maximum traction to the point that rotation was contained by ligament action
on the normal knee, before releases were performed. Then, we recorded the dynamometer
reading to determine the maximum force that could be applied to that specimen for
the rest of the experiment. The rotation force was applied after every release, until
the same value as the normal knee was obtained on the dynamometer. Assessment bias
was controlled in such way ([Fig. 3]). Measurements were taken as soon as the maximum rotation was attained.
Fig. 3 Anterior view of right knee showing the K-wires placed, (B) one on the roof of the femoral intercondylar and another placed on the anterior
tibial tuberosity. Maximum internal rotation was (A) performed using a dynamometer and (C) measured with a goniometer.
With the knee maintained at 90 degrees, we reached maximum internal rotation and measured
the angle between the two K-wires with a goniometer (PVC, 35 cm). Such data were collated
and grouped as Intact Anterior Cruciate Ligament (INT ACL). Continuing with the experiment,
the ACL was surgically cut ([Fig. 4]), and the same measurements were performed and collected in a group named Injured
Anterior Cruciate Ligament (INJ ACL).
Fig. 4 Anterior view of right knee in 90 degrees of flexion, the white arrow shows the section
of the ACL with the scalpel. The internal rotation of the tibia was then measured.
In the next stage of the experiment, the ITT was surgically cut proximally and reflected
inferiorly ([Fig. 2]). The researchers took care to avoid disturbing the site of ITT tibial insertion.
Measurements were obtained with the same technique as described previously, and data
were gathered in a group named Injured Anterior Cruciate Ligament associated to ITT
release (INJ ACL + ITT). At this stage of the procedure, once the ITT was reflected,
the ALL of the knee was dissected, applying a varus and internal rotation force at
30 and 60 degrees of flexion to elicit the effect of these structures under tension,
such as ALL, described as a resistance to such motion,[4] as shown in [Fig. 5].
Fig. 5 View of the lateral aspect of the right knee after dissection, anterior reflection,
and removal of the ITT. The ALL can be individualized and dissected, separating it
from the LCL. Next, we will cut the ALL and proceed to measure the internal rotation
of the tibia.
Once the area of interest containing the ALL had been exposed, the lateral collateral
ligament (LCL) and the popliteus tendon (PT) were identified ([Fig. 6]). The LCL was identified by palpation of its cylindrical structure at the site of
distal attachment to the fibular head, just above the biceps femoris tendon attachment.
Then, it was posteriorly exposed so that no tissue at the anterolateral aspect was
ruptured. In order to confirm that no part of the LCL had been mistaken for any other
additional structure, it was completely isolated from all other surrounding structures
by following its fibers from distal to proximal with a blunt dissector. Under this
ligament, the popliteus tendon was isolated and identified by traction of the popliteal
fibular ligament.
Fig. 6 View of the lateral aspect of the right knee showing the lateral structures of the
knee. From back to front, lateral gastrocnemius head (LG), lateral collateral ligament
(LCL), anterolateral ligament (ALL), and lateral meniscus (LM). The popliteal tendon
cannot be seen as they lie deep to LCL and ALL.
After identification of the LCL and PT, the ALL was recognized and identified by tensioning
its fibers and visualizing its femoral and tibial attachment sites. In the final stage
of the experiment, a transverse surgically section of the ALL was performed, and the
internal measurements were recorded, similar to previous stages of the experiment.
Data were gathered in a group named Injured Anterior Cruciate Ligament, severed Iliotibial
Tract, and severed Anterolateral Ligament (INJ ACL + ITT + ALL). The experimental
procedure was the same for both knees.
Statistical Analysis
Variables were described as the mean and standard deviation (SD). In order to compare
the range of motion among procedures, analysis of variance (ANOVA) was applied for
repeated measures, complemented by Bonferroni's post-hoc test where appropriate. The
adopted level of significance was set at 5% (p < 0.05), and analyses were performed with the IBM SPSS Statistics for Windows (IBM
Corp.) software, version 21.0. A t test for paired samples was performed to compare mean internal rotation measurement
values with the presence of ACL lesions and the addition of ALL sections. For this
analysis, we adopted a significance level of 1% (p < 0.001).
Results
The knee ALL was identified as a distinguished anatomical structure in all 38 specimens,
but only after the reflection of all ITT layers from its distal tibial attachment
site. In all 38 knees, the ALL insertion to the lateral meniscus could be anatomically
identified. Manipulation of the lateral meniscus in all directions showed that ALL
attachment fibers headed in the same direction as the lateral meniscus when this structure
was moved. Anterolateral ligament insertion over the tibia was, on average, halfway
between the midpoint of Gerdy's tubercle and LCL insertion into the fibular head.
The isolated cut of the ACL induced a significant increase (+55.6%, p < 0.001) in internal rotation of the knee at 90 degrees of flexion when compared
to the intact knee.
After ACL section, the association of ITT release induced a further increase of the
knee internal rotation at 90 degrees of flexion (+31.6%, p < 0.001), and a very significant increase (+104%, p < 0.001) when compared to the intact knee.
After ACL and ITT section, the additional ALL release induced a significant increase
in knee internal rotation at 90 degrees of flexion (+27.8%, p < 0.001), and when compared to the intact knee (+162%, p < 0.001).
A significant increase in knee internal rotation was observed as the ligament releases
were performed. The specific section of the ACL led to a 55.6% increase in the mean
internal rotation of the knee in relation to the femur when compared to the mean of
the intact ACL group.
The addition of the ITT release increased the mean internal rotation of the knee by
up to 102%. Finally, after the additional section of the ALL, the mean internal rotation
of the knee increased even further, up to 162%.
There was a significant difference between the mean internal rotation measurements
(21.13 ± 3.68) obtained for the isolated section of the ACL when compared to the mean
internal rotation (35.57 ± 6.81) obtained when an ALL section was added ([Table 1]). Therefore, this association created a 68.3% increase in internal rotation when
compared to the measurements after the isolated section of the ACL ([Table 2]).
Table 1
Rotational differences after serial section in 90 degrees of flexion
|
Range of motion
|
INT ACL
|
INJ ACL
|
INJ ACL +ITT
|
INJ ACL + ITT +ALL
|
p-value
|
|
Mean ± SD
|
Mean ± SD
|
Mean ± SD
|
Mean ± SD
|
|
|
Right knee internal rotation
|
13.6 ± 3.9
|
21.0 ± 3.8
|
27.4 ± 5.0
|
36.5 ± 7.4
|
< 0.001
|
Abbreviations: INJ ACL, injured anterior cruciate ligament; INJ ACL + ITT, injured anterior cruciate
ligament and iliotibial tract; INJ ACL + ITT + ALL, injured anterior cruciate ligament,
iliotibial, tract, and anterolateral ligament; INT ACL, intact anterior cruciate ligament;
SD, standard deviation.
Note: The table indicate a statistical difference at a level of 5% by Bonferroni's post
hoc test.
Table 2
Increased internal knee rotation after sequential ligament releases
|
Condition
|
Mean ± SD
|
|
Displacement (%)
|
|
INT ACL
|
13.57 ± 4.195
|
|
0
|
|
INJ ACL
|
21.13 ± 3.684
|
|
55.6
|
|
ACL + ITT
|
27.81 ± 4.543
|
|
104
|
|
ACL+ ITT + ALL
|
35.57 ± 6.812
|
|
162
|
Abbreviations: ACL + ITT, anterior cruciate ligament and iliotibial tract-associated injuries; ACL + ITT + ALL,
anterior cruciate ligament, iliotibial tract, and anterolateral ligament-associated
injuries; INJ ACL, isolated anterior cruciate ligament injury; INT ACL, intact anterior
cruciate ligament; SD, standard deviation.
Note: Comparison of means, standard deviation and percentage of anterolateral displacement
of internal rotation between groups.
The INJACL group (isolated ACL deficiency) had lower internal knee rotation (p < 0.001) when compared with the ACL injury associated with the INJ ACL + ITT + ALL
group.
This experiment shows a pronounced increase in the internal knee rotation, when the
ALL injury was added to the ACL-deficient side, related to the release of the ALL.
Discussion
Isolated ACL sections show a significant increase of the internal rotation of the
knee at 90 degrees of flexion when compared to the intact knee. The associated ITT
release on an ACL-deficient knee induced a further significant increase in the internal
rotation of the knee at 90 degrees flexion when compared to an intact knee, highlighting
its relevance. An additional ALL release significantly increased the knee internal
rotation.
Our study demonstrated that there is a significant increase in knee internal rotation
with ACL and ALL insufficiency and a severed ITT, suggesting that there is no specific
structure that controls knee rotation. Nonetheless, our results demonstrate that ALL
deficiency increases rotational instability when compared to the ACL and ITT sections.
It is known that anterolateral structures are important restraints of knee internal
rotation,[4]
[10]
[11] and act in synergy with the ACL.[12]
The “clunk” produced on the pivot-shift test seems to have a weak correlation with
the association of ACL and these structures injury.[13] Monaco et al.[13] were the first to hypothesize the relevance of the ALL among other anterolateral
knee structures. A study by Parsons et al.[14] demonstrated that the contribution of the ALL increases significantly with increased
knee flexion, while the ACL significantly reduces its contribution. The contribution
of the ALL overcomes that of the ACL after 30 degrees of knee flexion. They concluded
that the ALL is an important internal rotation stabilizer of the knee after 35 degrees
of flexion. Sonnery-Cottet et al.[9] confirmed and stressed the involvement of the ALL in knee internal rotation control
among the anterolateral structures.
In cases of ACL rupture, the rotational axis is displaced towards the medial compartment
of the knee, increasing not only the anterior translation of the tibia over the femur,
but also the internal rotation of the lateral compartment.[10] As a result, a significant increase in anterolateral structure recruitment is required
to constrain such motion. The findings of our study confirm this, as seen in [Table 1]. Insufficient postoperative rotatory control, seen after classic ACL reconstruction,
could be caused by modification of the knee rotation center, but also due to the association
with a lesion of its anterolateral structures.[15]
A recent publication that reported the outcomes of ACL associated with ALL reconstruction
with a follow-up lasting more than 2 years presented promising results in terms of
clinical outcomes and rotational control.[16] Interestingly, in that series, the rate of contralateral ACL lesion (6.6%) was similar
to that described in the literature, but the rate of graft rupture associated with
ALL reconstruction (1.1%) was lower than previously published rates,[17]
[18]
[19] demonstrating that such an association may be extremely beneficial in some cases.
Regarding primary and secondary restraints, the failure of a primary restraint will
lead to the recruitment of secondary structures to resist external forces and stabilize
joint motion. In a study on the ALL, Dodds et al.[20] demonstrated that tibial internal rotation relative to the femur increases the distance
between their insertions in that ligament, leading to tightening. The authors reported
that the persistence of rotatory instability after ACL reconstruction could result
from a failure to correct insufficiency of the anterolateral structures. Our study
has shown that, in knees with ACL section (21.13 ± 4.19), that is, with simple anterolateral
rotational instability, an additional ALL release (35.57 ± 6.81) significantly increased
internal rotation (p < 0.001).
This study has some limitations. The sequence of dissections might have over- or underestimated
the individual stability of each component, due to interactions among those anatomical
structures, which could not be assessed solely through the dissection technique. The
measurement method is not electronically precise in data collection (such as navigation).
However, all measurements were submitted to a rigid execution protocol and were always
performed by the same researcher. We did not isolate or test Kaplan's fibers from
the ITT, nor test the rotations through different force torques. Thus, our results
may depend on the loads applied to those structures.
Despite meticulous dissection of the ITT, the ALL could have been injured, which would
modify the results. We did not test an isolated section because this condition does
not occur clinically. The association between ALL and LCA release was not assessed,
as this is not yet possible. This is due to the impossibility of isolating the ALL
in order to perform its release, without first retracting the ITT strictly following
the dissection technique, as was widely discussed by Sonnery-Cottet et al.[9]
Conclusion
The ACL injury increases the knee's internal rotation. There is a demonstrated correlation
between the ACL and ALL injury, leading to a pronounced increase in internal rotation
when compared to the uninjured knee (above 100%). Therefore, the presence of pronounced
internal rotation of the knee is a clinical sign of associated injury to these structures,
which can assist surgeons in the diagnosis and guide appropriate treatments.
Bibliographical Record
Geraldo Luiz Schuck de Freitas, João Luiz Ellera Gomes. The Measure of Internal Rotation
of the Knee in the Clinical Diagnosis of Association of Anterolateral Ligament and
Anterior Cruciate Ligament Injury. Rev Bras Ortop (Sao Paulo) 2025; 60: s00451811632.
DOI: 10.1055/s-0045-1811632
