Performing the One-Leg Rise Test to Assess Quadriceps Strength after ACLR
This study examined the usefulness of the one-leg rise test to assess quadriceps strength after ACLR
The one-leg rise test was associated with the force measured through the gold standard isokinetic strength testing
This test may be an important evaluation tool, especially early in the rehabilitation after ACLR
Introduction
The cornerstone of rehabilitation following an anterior cruciate ligament injury, whether it is treated surgically or managed nonoperatively (ACLR), is the restoration of quadriceps strength. Several measurement options exist, such as measuring isometric or isotonic strength, the latter being the gold standard. A limitation of these gold-standard measurement methods is that they require specialized and oftentimes expensive equipment. Hop tests have been previously found associated with quadriceps strength, but in the initial phases of an ACL injury, these are inappropriate to use. One-repetition maximum testing and dynamometry can be used, but also require specialized equipment. Since this is not always accessible in the rehabilitation context, it would be interesting to develop field tests that can reliably measure strength. The one-leg rise test is such a field test that has been developed to assess quadriceps strength after ACLR, but to know whether this truly reflects someone’s quad strength, this study was set up.
Methods
The current study was derived from the ongoing SUPER-Knee randomized controlled trial. A cross-sectional analysis of baseline data from the first 50 female and 50 male participants was used. They had received ACLR surgery in the previous 9-36 months and had a healthy, contralateral knee without a history of prior surgery.
This ongoing SUPER-Knee RCT investigates if SUpervised exercise therapy and Patient Education Rehabilitation (SUPER) is superior to a minimal intervention control for improving pain, function, and quality of life in young adults with ongoing symptoms following ACLR. The participants were between 18 and 40 years old when they underwent the ACLR surgery and reported a symptomatic knee, which was defined as having a mean KOOS score on the pain, symptoms, function in sports/recreation, and quality of life domains (KOOS4) below 80/100.
The included participants performed the one-leg rise test to assess quadriceps strength after ACLR. They were seated on a height-adjustable plinth with the heel of their foot 10 centimeters in front of the edge of the plinth, assuring their knee was at an angle of 90°.
They received the instruction to get up standing and squat back down until they lightly touched the plinth. They had to repeat it for as many times as possible. The rate of repetitions followed a metronome beat set at 45 beats per minute (one beat up and one beat down). In case 3 protocol violations occurred (touching the ground with the opposite foot, loss of pace with the metronome, or uncontrolled contact with the plinth) or when the participant stopped, the test was ended. The number of repetitions was recorded and it was asked what kept them from performing more repetitions. The test was repeated on the other side. Both sides were compared using the calculation of a limb symmetry index by dividing the number of repetitions in the ACLR knee by the contralateral knee and multiplying by 100.
Thereafter, the participant was tested on the isokinetic dynamometer with their leg positioned at 60° of knee flexion. Participants sat with the non-test leg and trunk stabilized to the chair and the test leg strapped to the stationary arm immediately proximal to the superior lateral malleolus. After a warm-up trial at 50% of maximal effort was performed to familiarize the participants with the test, they were instructed to kick the leg away as hard and as fast as possible. Three trials were completed and were separated by a 1 minute rest period. The highest peak torque was recorded and normalized to body weight. Also here, the limb symmetry index was calculated.
Results
A total of 100 participants (50 males and 50 females) were included in this study. They were on average 30 years old and had a mean BMI of 27 kg/m2. The median of the sample was at 31 months following ACLR (interquartile range IQR 24-35).
They performed a median of 13 (IQR 9-20) and 17 (11-24) repetitions on the one-leg rise test on the ACLR and uninjured limb respectively. The isokinetic strength measurement to assess quadriceps strength after ACLR revealed a mean strength of 2.09 Nm/kg and 2.33 Nm/kg on the ACLR and uninjured leg respectively.
When the relationship between the one-leg rise test and the isokinetic strength measurement was examined, the authors observed that both measurements were associated. This association was observed in both the ACLR and uninjured leg.
Questions and thoughts
An important aspect to highlight is the difference in measurement methods. To assess quadriceps strength after ACLR in this study, the measurements of quadriceps strength differed. The gold standard measurement requires force production at 60° of knee flexion whereas the one-leg rise test was executed starting at 90° of knee flexion. Also, the gold standard measurement is an open kinetic chain movement and it was compared to a closed kinetic chain test. Since this difference may affect joint biomechanics, it is possible that these are not directly comparable. There is on the other hand no issue for not performing these open kinetic chain movements, as these were found not to increase graft laxity (Forelli et al. 2023).
The highest peak torque on the isokinetic biodex machine was used to quantify the strength, rather than the mean of the three repetitions. Fear and hesitancy can have impacted strength production, so I understand they use the maximal recorded strength value to be as representative of the maximal strength as possible. Other studies measuring muscle force frequently use a mean value, so this has to be borne in mind when comparing results across such studies.
What was interesting about this study was the prediction of the quadriceps strength by the result of the one-leg rise test. Using the table here under, you can see that for every repetition of the one-leg rise test, the quadriceps strength can be estimated for the ACLR or uninjured limb.
The rate of increase in quadriceps strength decreased at higher values of the one-legged ascent performance. This means that the prediction of quadriceps strength from the number of repetitions on the one-leg rise test is especially useful when fewer repetitions can be done. This suggests that performance on the one-leg rise test can provide a meaningful indication of quadriceps strength, especially in less functioning individuals.
Talk nerdy to me
The table above is an estimate of the quadriceps strength, derived from the number of repetitions in the one-leg rise test. The authors mentioned that the performance on the one-leg rise test explained around 40-50% of the variance in the quadriceps strength. Other factors such as balance, motivation, and muscular endurance over a prolonged period, compared to a quick and isolated 5-second movement on the isokinetic biodex machine. Importantly, the associations between the one-leg rise test and the quadriceps strength were irrespective of the knee injury of surgery history (with or without meniscal procedure) and the presence of knee symptoms.
The authors had no data beyond 35 repetitions of the one-leg rise test. Therefore we cannot say whether or not there is a ceiling effect. It is however, important to note that when someone achieves a higher number of repetitions, this can significantly protect the knee for the development of knee OA 5 years later, even when this was controlled for age, sex, BMI, and baseline pain as studied by Thorstensson et al. (2004).
The performance on the one-leg rise test was reported to be limited by fatigue, not only in the quadriceps but also in the gluteal muscles. This may also represent that another movement strategy is used to complete the task. But pain can equally be a limiting factor. To enhance performance on this test, not only knee-dominant but also hip-focused exercises would be recommended.
Take home messages
The one-leg rise test was able to Assess Quadriceps Strength after ACLR in this sample of young adults. This test was related to the force outcomes measured by the gold standard isokinetic biodex). This way, you can estimate someone’s strength without the need for specialized equipment. This method was especially suited for low-functioning individuals since the prediction of quadriceps strength from the number of repetitions on the one-leg rise test was more accurate when fewer repetitions could be done.
Reference
Additional reference
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