Q-angle: a factor in peak torque occurrence in isokinetic knee extension*

Correlation between the Q angle and the isokinetic knee strength and muscle activity

OBJECTIVES

The aim of this study was to investigate the correlation between the Q angle and the isokinetic knee strength and muscle activity.

PATIENTS AND METHODS

Between March 2016 and April 2016, a total of 50 healthy and right-leg dominant men (mean age 22.3±2.3 years; range, 18 to 27 years) with a Q angle between 5° and 20° and active in sports were included. An isokinetic strength test of the knee joint extensor and flexor muscles at angular velocities of 60, 120, 180, 240, and 300°·s-1 was tested who had a Q angle of 5 to 20° and were active in sports. Surface electromyography (sEMG) was used to determine these muscles' activity levels.

RESULTS

Negative correlations were between the Q angle and the average peak torque (APT) in extension (E) and flexion (F), the average power (APE,F) at all angles, the joint angle at the PT (JAPTE) at 240, 180, 120 and 60°·s-1; JAPTF at 300, 240 and 180°·s-1; and the time to PT (TPTF) at 180°·s-1. There was a positive correlation between the Q angle and TPTE (at 60°·s-1). No significant relationship between the Q angle and the level of EMG activity at any angular velocity of the muscles, as well as the VM:VL EMG activity ratio was found.

CONCLUSION

A higher Q angle is associated with decreased isokinetic knee strength, power output, and torque angles. It is thought that possible high Q angle-related knee joint disorders and sports injuries can be avoided by including proper quadriceps strength exercises in exercise prescriptions to be prepared.

The biomechanics of the patellofemoral joint

Physical therapy for patella malalignment differs from therapy for other knee conditions. In fact, accepted forms of knee therapy can be counterproductive when one is dealing with patella malalignment. This article reviews some of the biomechanical foundations of patella-specific therapy and addresses common controversies. We emphasize the concept of articular cartilage stress over that of joint reaction force. The rationale for strengthening the vastus medialis obliquus and for avoiding certain forms of open chain strengthening are discussed, and we outline some of the exciting work being done in our laboratory concerning patellofemoral tracking, contact area, and cartilage properties.

Q angle: effects of isometric quadriceps contraction and body position

The quadriceps femoral angle (Q angle) has been linked with several knee disorders, but Q-angle measurement procedures have not been standardized. The purpose of this study was to examine the effects of isometric quadriceps contraction in the standing and supine positions on the Q angle. The Q angles of the right knees of 30 men and 30 women were measured goniometrically during four test conditions: 1) quadriceps relaxed in standing, 2) quadriceps contracted in standing, 3) quadriceps relaxed in supine, and 4) quadriceps contracted in supine. The pelvic widths were also measured as the distance between the anterior superior iliac spines in standing and supine. A two-way multivariate analysis of variance showed a significant difference between genders (p < 0.001) and among the four test conditions (p < 0.001) (N = 60). Separate one-way analyses of variance (ANOVAs) with two grouping factors (contraction and position) showed significant effects of contraction (p < 0.001) for both men and women, but no significant effect of positions. A dependent t-test showed that the pelvic width differed between standing and supine for both men and women (p < 0.001). The results showed that isometric quadriceps contraction affects the Q angle with the subjects standing or supine, even though the pelvic width differed significantly between the two positions. Clinicians and researchers should consider the results of this study in order to standardize procedures for measuring the Q angle.

Maximal peak torque as a predictor of angle-specific torques of hamstring and quadriceps muscles in man

This study assessed the relationship between the isokinetic peak torque (PT) (speed of movement 1.05 and 3.14 rads-1) and the angle-specific torques (ASTs) at 0.26 and 1.31 rad of knee flexion in multiple contractions of the quadriceps and hamstrings in 70 individuals with a chronic anterior cruciate ligament (ACL) insufficiency and 78 individuals with a chronic medial collateral ligament (MCL) insufficiency in one knee. At every test speed, the Pearson product moment correlation coefficients (r) between the PT and ASTs were highly significant (P less than 0.001) in the uninjured knees (r = 0.61-0.93) as well as in the knees with ACL (r = 0.61-0.87) and MCL (r = 0.74-0.91) insufficiency. In addition, in both groups the majority of the correlation coefficients exceeded 0.80, which is generally regarded as the threshold for the relationship to be considered clinically significant. Furthermore, using regression analysis, both extremities showed completely non-systematic distribution of the residuals. It is concluded that in healthy knees or knees with ACL or MCL insufficiency, the predictability of ASTs from PT was good, and, therefore, that AST analyses may offer little additional information about thigh muscle function to that obtained from a simpler and more commonly used measurement, the PT analysis.

Relationship between Peak Torque and Angle-specific Torques in an Isokinetic Contraction of Normal and Laterally Unstable Knees

This study assessed the relationship between the isokinetic peak torque (PT) (speed of movement, 60 degrees /sec and 180 degrees /sec) and the angle-specific torques (ASTs) at 15 and 75 degrees of knee flexion in multiple contractions of the quadriceps and hamstrings in 21 subjects having a chronic lateral collateral ligament (LCL) insufficiency in one knee. At every test speed, the Pearson product moment (r) correlation coefficients between the PT and ASTs were highly significant (p < 0.001) in the uninjured (r = 0.66-0.92) as well as in the LCL insufficient (r = 0.78-0.88) knees. In both extremities, the majority of the correlation coefficients exceeded 0.80, which was the threshold set before the study for the coefficients to be exceeded before the relationship could be considered clinically important. Using regression analysis, both extremities showed completely nonsystematic distribution of the residuals. In conclusion, concerning healthy or LCL-insufficient knees, the correlations between PT and ASTs were high and consistent. Therefore, AST analyses may offer little additional information about thigh muscle function to that obtained through a simpler and more commonly used measurement, the PT analysis. J Orthop Sports Phys Ther 1991;13(2):89-94.