The relationship between knee strength and functional stability before and after anterior cruciate ligament reconstruction

Abstract

Functional stability of the knee is dependent on an intact ligamentous system and the timely and efficient contraction of supporting musculature. The aim of this study was to assess the relationship between muscle strength and functional stability in 31 patients pre-and post-operatively, following a unilateral anterior cruciate ligament rupture. All subjects underwent reconstructive surgery using semitendonosis and gracilis tendons. Isokinetic strength assessment of quadriceps and hamstring muscles was performed at a rate of movement of 6Oo/s and 120°/s. Functional stability was determined by performance during five functional stability tests that included the shuttle run, side step, carioca, single and triple hop tests. Pearson's correlation coefficient statistics were applied to pre-operative and post-operative data respectively. These analyses demonstrated a significant positive correlation between quadriceps strength indices at both testing speeds and the two hop tests pre-operatively (p's < 0.007) and between quadriceps strength indices at both speeds and all five functional tests post-operatively (p's < 0.01). Assessed using Steiger's formula, there was a significant increase in the correlation between quadriceps strength indices and three functional tests post-operatively compared to pre-operatively (p < 0.05). No significant correlation between hamstring strength indices and functional scores existed pre-or post-operatively. This study has shown a significant correlation exists between quadriceps strength indices and functional stability both before and after surgery, this relationship does not reach significance between hamstring strength indices and functional stability.

The Relationship Between Pre-Operative and Twelve-Week Post-Operative Y-Balance and Quadriceps Strength in Athletes With an Anterior Cruciate Ligament Tear

“…Extensive research demonstrates quadriceps deficits can be present at six months and even up to and exceeding one year. [1][2][3][4][5] Quadriceps strength has recently been shown to help predict reinjury rate. Grindem et al 20 found that individuals following ACL-R with a quadriceps strength deficit of greater than 10% are significantly more likely to reinjure their ipsilateral ACL.…”

“…However, it is well documented that quadriceps strength deficits may remain for two years and beyond, following ACL-R. [1][2][3][4][5] Multiple authors have shown that those individuals with greater quadriceps strength pre-operatively have significantly greater quadriceps strength at RTS, and those with lower quadriceps strength pre-operatively have lower functional scores on single and triple hop tests (time and distance) at time of RTS and may take longer to RTS after ACL-R. 1, 2,6 Quadriceps strength is important as it relates to outcomes and performance at time of RTS. 2,7 Recently, researchers have found that decreased quadriceps strength, and larger asymmetries between limbs, lead to shorter distances on hop tests. 1,8 This suggests that strength deficits and side to side symmetry are important to consider when looking at readiness to RTS.…”

Is there any correlation between functional and clinical tests in anterior cruciate ligament reconstructed knees after three years?

“…According to one study, quadriceps strength indices were positively correlated with hop tests 1 week before and 6 months after reconstruction; hamstring strength indices were correlated with hop tests 6 months after reconstruction. 17 A different study supported the relationship between single-legged hop distance and quadriceps strength, but not with flexor strength.…”

Return to Sport after Anterior Cruciate Ligament Reconstruction: A Literature Review

“…The same authors concluded that quadriceps strength deficits of more than 15% are negatively correlated with function and performance after ACL reconstruction. Although hamstrings are considered very important for the stability of the knee, there is no impact of hamstrings strength deficit on the performance of functional tests [68]. Yet, hamstrings are very important not only for flexing the knee but also for reducing the ACL strain [69][70][71] and their strengthening should be of high importance.…”

“…The acceptable deficit on muscle strength before returning to sport as described by different authors varies from study to study but rates between 10% to 35% [41, 68,[72][73][74][75]. Ekstrand [71] suggested that the athlete before return to team training should have regained at least 90% of the muscle strength.…”