Bilateral Medial Tibiofemoral Joint Stiffness in Full Extension and 20° of Knee Flexion

Abstract

Context:The valgus stress test is used clinically to assess injury to the medial knee structures in 2 positions: full extension and some degree of flexion. The amount of flexion used to ''isolate'' the medial collateral ligament is not consistent in the literature, but most studies have shown that stiffness of the ligaments was consistent between the limbs.Objective: To determine (1) if the stiffness of the medial knee structures was the same bilaterally, and (2) if the stiffness was different in full extension compared with 206 of knee flexion.Design: Criterion standard, before-after design. Setting: University research laboratory.Patients or Other Participants: Both knees of 45 healthy and active volunteers (26 females, 19 males; age 5 23.2 6 3.96 years, height 5 170.6 6 7.75 cm, mass 5 74.2 6 15.14 kg) were studied.Intervention(s): A valgus force of 60 N was applied to the lateral aspect of both knees in full extension and in 206 of flexion. Main Outcome Measure(s):The slope of the force-strain line of the medial knee during a valgus force was calculated using the LigMaster arthrometer.Results: Slope means in full extension were 16.1 6 3.3 (right knee) and 15.8 6 3.1(left knee). Means for 206 of flexion were 12.2 6 3.1 (right) and 11.7 6 2.8 (left). Stiffness was greater when the knee was in full extension versus 206 of flexion (t 44 5 12.04, P , .001). No difference was noted between the slopes of the 2 knees in extension (t 44 5 0.74, P 5 .46) or in flexion (t 44 5 1.2, P 5 .27).Conclusions: These findings support the use of the contralateral knee as a control. Further, the valgus stress test should be performed in full extension and in some degree of flexion to assess the different restraining structures of the medial tibiofemoral joint.

Tibiofemoral Joint Positioning for the Valgus Stress Test

“…We applied a valgus force to the medial tibiofemoral joint while the resistance was calculated and represented by the slope of the force-strain line generated by the software (version 1.33) embedded in a LigMaster arthrometer (Sport Tech Inc, Charlottesville, VA). We 28 have reported on repeatability and reliability of this arthrometer in a previous paper.…”

“…positioned and performed all measurements on each volunteer in a single session. Specific positioning has been previously described 28 and is shown in Figure 1.…”

“…We have found that holding the limb and joint in a small amount of flexion is more manageable than maintaining a larger amount of flexion while applying a valgus stress. In our initial study 28 on this topic, we found a difference in the resistance of the medial tibiofemoral joint when measured in full extension and at 206 of flexion using an arthrometer, but we did not determine the specific angle between 06 and 206 at which the slope of the force-strain line differed from extension. The purpose of our current study was to identify the tibiofemoral joint angle between 06 and 206 of flexion at which the slope of the force-strain line differs for the medial knee structures.…”

Medial Tibiofemoral-Joint Stiffness in Males and Females Across the Lifespan

“…The positioning of each participant has been described previously in detail. 24,25 We positioned and secured the side arms of the LigMaster in place at equal distance from the pressure plate and just superior to the lateral aspect of tibiofemoral joint line. In addition, we positioned the side arms closer to the pressure plate in the children to accommodate shorter legs ( Figure 2).…”

“…Examining the material properties of a ligament, such as stiffness, provides a way to detect joint structural differences between sexes and across age groups, thus elucidating structural differences in the ligament material properties secondary to the exposure to sex hormones. Aronson et al 24,25 measured stiffness of the medial tibiofemoral joint in full extension because of the important role the medial joint structures play in minimizing valgus positioning (abduction of the joint), which has been suggested to contribute to ACL injury risk. 3,5,[15][16][17] Additionally, Aronson et al 24,25 examined the extracapsular MCL in 208 of flexion to reduce the confounding contributions of possible changes in intracapsular structures, such as meniscal injury and articular degeneration, to stiffness measurements.…”