Clinicians routinely quantify and track joint range of motion (ROM) as part of the evaluation and rehabilitation process. Limitations in tibial ROM are often overlooked due to the difficulty in measuring transverse plane motion (Makowski et al., 2005). The embedded compass app of an iPhone (iPhone 6 model A1549, Apple, Inc., Cupertino, CA, USA) has recently been shown to reliably assess tibial internal and external rotation ROM making it convenient and easy to quantify (Stanek et al., 2020). Rotational motion at the tibia is essential for knee and ankle function and is often implicated as a compensatory strategy for various lower extremity conditions (Bell-Jenje et al., 2015; Bonci, 1999; Griffin et al., 2000; Matsumoto et al., 2000; Zhang et al., 1993). Previous authors have described tibial rotation as an important, yet often understudied (Makowski et al., 2005; Matsumoto et al., 2000; Zhang et al., 1993). A thorough understanding of rotational motion of the tibia contributes to an accurate evaluation of knee mobility, as well as provides a better understanding of function at the hip, ankle, and foot.

A previous investigation described potential complications from abnormal variations in tibial rotation (Lusin and Gajdosik, 1983). These pathologies include the development of chondromalacia patella and other degenerative joint changes. Alterations in tibial rotation have also been implicated with meniscal lesions and injuries to the cruciate ligaments (Hallen and Lindahl, 1966). Furthermore, tibial external rotation, along with anterior translation of the knee, and hindfoot eversion have been implicated with dynamic valgus at the knee (Bell et al., 2008; Hewett et al., 2006). This positioning has been correlated with iliotibial band syndrome (Ferber et al., 2010), patellofemoral pain syndrome (Levinger et al., 2006; Molgaard et al., 2011), tibial stress fractures (Milner et al., 2006), posterior tibial tendon dysfunction (Ness et al., 2008), anterior cruciate ligament tears (Powers, 2010), and osteoarthritis of the knee (Chang et al., 2005).

Much of the previous literature has focused on the relationship between hip and knee alignment, especially as it relates to dynamic valgus. However, a more recent study found individuals with <17° of ankle dorsiflexion (DF) exhibited 6.5° higher hip adduction angles during an elevated step down task (Bell-Jenje et al., 2015). Interestingly, the higher hip adduction angles were normalized to the group with >17° DF with a heel lift, suggesting that lost DF ROM contributed to the valgus knee positioning. During normal lower extremity biomechanics, several motions must couple in order to achieve optimal function. For example, during closed-chain activities, the tibia must internally rotate (IR) to allow ankle DF and pronation to occur (McClay and Manal, 1997). Loss of DF ROM is commonly observed in both the athletic and general population and is believed to be a predisposing factor for lower extremity injury (Backman and Danielson, 2011; Neely, 1998; Tabrizi et al., 2000; Wang et al., 2006; Willems et al., 2005; You et al., 2009). Typically, DF ROM deficits are believed to be caused by tightness of the triceps surae, a decrease in the posterior glide of the talus, and/or accessory motion loss at the tibiofibular, subtalar, and/or midtarsal joints (Denegar and Hertel, 2002; Leanderson et al., 1993). Because the motions of DF and T-IR are coupled, lost T-IR could also contribute to deficits in DF ROM. Despite wide ranges in reported normative values for T-IR (Lusin and Gajdosik, 1983; Makowski et al., 2005; Stanek et al., 2020), findings from a previous study using the compass app showed average T-IR ROM to range from 12°–14° (Stanek et al., 2020). Anecdotally, clinicians have been performing techniques to restore T-IR and potentially improve ankle DF. Several variations of the technique using elastic bands have been published in blog or online video posts (Physical Therapy Nation, YouTube, San Bruno, CA, USA) to provide guidance for how to perform the technique, however, no peer-reviewed, published literature exists to support their efficacy. Furthermore, the use of elastic bands, such as the VooDoo floss band (Rogue Fitness, Columbus, OH, USA), is scarce amongst the literature (Kiefer et al., 2017). Therefore, the purposes of this exploratory study were to determine the effectiveness of a manual therapy, mobilization with movement (MWM) technique for improving T-IR and secondarily to examine the relationship between T-IR and DF ROM. We hypothesized that the manual therapy technique would immediately improve T-IR ROM. We also hypothesized that T-IR and DF ROM would be positively correlated.

Descriptive statistics for all data are included in Table 2. There was a statistically significant amount of T-IR increase following the intervention for the manual therapy group (m=2.03°±2.24°) when compared to the control group (m=0.62°±2.61°); t(40)= 3.53, P=0.001, effect size=1.09, 95% confidence interval=0.44–1.74. There were no significant changes in standing (t[40]=0.04, P=0.97) or kneeling (t[40]=0.81, P=0.42) DF ROM. No significant correlation was found between T-IR and both standing (r=0.20, P=0.20) and kneeling (r=0.14, P=0.39) DF ROM (Figs. 4, 5).

The purpose of this study was to investigate the effectiveness of a manual therapy technique aimed at improving T-IR ROM and examine the relationship between T-IR and DF ROM. Our hypotheses were only partially supported. Results showed a single session of manual therapy can increase T-IR ROM but it had no effect on DF ROM. Additionally, end-range T-IR and DF ROM do not appear to be associated as there were small, nonsignificant correlations between T-IR and both standing and kneeling DF ROM. Because of the test position for the manual therapy technique, we chose to assess both standing and kneeling DF in the event the intervention had a different impact on these measures. However, results showed neither standing nor kneeling DF ROM was impacted from the intervention.

Manual therapy interventions are commonly used within rehabilitation settings, often with the goal of improving mobility. The manual therapy MWM technique employed in this study has been demonstrated online as a method for improving T-IR. Due to the nature of the technique, it is not surprising that it can increase motion since the technique passively moves the tibia into IR with each repetition. However, the weightbearing technique also passively moves the ankle into DF, therefore it was surprising to see no changes in DF mobility. It is possible the participants in this study had adequate DF mobility, creating a ceiling effect for further increases in DF ROM. A study among people with restricted DF mobility may have shown different results.

Reduced ankle DF ROM is a commonly found deficit within athletic and non-athletic populations and is commonly observed in patients following a lateral ankle sprain (Denegar et al., 2002; Hertel, 2002; Hubbard and Hertel, 2006; Tabrizi et al., 2000). However, reduced DF is also a risk factor for sustaining a lateral ankle sprain, therefore, numerous interventions for improving DF ROM have been studied (Terada et al., 2013). Traditionally, treatments for DF ROM deficits include the use of joint mobilizations for restoring the proper accessory motion, stretching of the triceps surae, modalities, or a combination of these therapies (Young et al., 2013). To our knowledge, no previous studies have examined the impact of T-IR ROM on DF mobility. Because previous studies have demonstrated the coupled motions of knee flexion, T-IR, and ankle DF ROM during functional tasks such as squatting or during gait (Bell-Jenje et al., 2015; McClay and Manal, 1997), we hypothesized that improving T-IR may also positively affect DF ROM. However, while the manual therapy intervention was effective at improving T-IR rotation in the short-term, it does not appear that this resulted in an increase in DF ROM.

Tibial IR ROM is not commonly quantified in the clinical environment, yet rotational motion at the tibia is essential for knee and ankle function and is often implicated as a compensatory strategy for various lower extremity conditions (Bell-Jenje et al., 2015; Bonci, 1999; Griffin et al., 2000; Matsumoto et al., 2000; Zhang et al., 1993). A previous reliability study using the same measurement technique showed average T-IR ROM to be approximately 13° with SEM ranging from 2.24–2.82 (Stanek et al., 2020). Because of the large standard deviations in the reliability study, the SEM was high. Using data from the current study and using the formula SEM=standard deviation x-√1-r, with r as the reliability of the measurement, the calculated SEM was 1.46. Collectively, participants in the current study started with approximately 8° of T-IR and participants in the intervention group reached values around 9.3°. Participants in the intervention group demonstrated over a 2° change in ROM with large effect sizes. These findings suggest clinically meaningful changes in T-IR ROM, however, additional research to support these findings is needed. Methods and instrumentation for assessing T-IR ROM vary greatly throughout the literature. Therefore, it is important for clinicians to have the ability to quantify and address limitations when necessary. Our results suggest this technique could be a simple, yet effective method for increasing T-IR in the short term.

This study is not without limitations. First, we measured active, end-range T-IR and DF ROM. While previous authors have demonstrated these motions are coupled during functional tasks, it is possible T-IR occurs early within the functional task and maximum IR occurs prior to end-range DF ROM. Therefore, increasing the T-IR did not have a substantial effect on end-range DF ROM. Secondly, we used a healthy population with limited T-IR ROM, but normative values of T-IR vary considerably. Previously forthcoming work using similar methodology showed T-IR values between 12°–14° (Stanek et al., 2020). Our inclusion criteria required participants to have less than 12° of T-IR to potentially prevent a ceiling effect with the manual therapy MWM technique. Because of the wide variability within previously published normative values for T-IR (Lusin and Gajdosik, 1983; Makowski et al., 2005), less than 12° may not be a sufficiently restricted degree of mobility for T-IR. Furthermore, our population did not have a DF ROM deficit. It is possible our results for changes in DF ROM would have been different if we recruited a population with a known T-IR and DF deficit. Future research is needed to quantify consistent and accurate values for normal tibial rotation mobility. Furthermore, additional research should examine the effects of this manual therapy technique on functional tasks such as gait or squatting. Lastly, we compared a single treatment to a true control condition receiving no intervention. It is possible comparing to another intervention or a placebo intervention could have resulted in different findings.

In conclusion, a single manual therapy, MWM treatment is effective at increasing T-IR ROM in the short-term compared to no treatment. However, it did not affect closed-chain DF ROM. Clinicians are encouraged to examine tibial rotation mobility within their patients for potential deficits. Patients with deficits in T-IR mobility may benefit from using this manual therapy technique.