KEA vs Towel for Early Quad Activation Post Anterior Cruciate Ligament Reconstruction

BACKGROUND Rupture of the anterior cruciate ligament (ACL) and its surgical reconstruction are followed by substantial deficits in quadriceps muscle function. In the early postoperative period, reflexive inhibition of the quadriceps, known as arthrogenic muscle inhibition (AMI), leads to drastically reduced voluntary muscle activation. Quadriceps activation failure contributes to weakness, which is concerning since quadriceps strength is strongly related to knee function and stability. Without effective intervention, patients can experience persistent strength deficits, delayed functional recovery, and even altered knee biomechanics due to inadequate quadriceps activation. Notably, one study reported that by 2 weeks after ACL reconstruction, the electromyographic (EMG) activation amplitude of the vastus medialis was less than 50% of normal levels, highlighting the severity of early postoperative quadriceps inhibition.

Early rehabilitation therefore prioritizes reactivation of the quadriceps. Standard ACL rehabilitation protocols universally include quadriceps setting exercises beginning immediately after surgery. Quadriceps setting is an isometric contraction of the knee extensors (quadriceps) with the knee in extension, often performed with a rolled towel or bolster placed under the knee to provide a slight knee flexion angle and a target to press down against. This simple exercise is aimed at recruiting the quadriceps muscle and counteracting AMI as soon as possible. Clinical guidelines and expert consensus recommend initiating such isometric quadriceps contractions on post-op day 1 to restore active knee extension and prevent loss of motion. The conventional method using a rolled towel under the knee is easy and requires no special equipment; however, it provides minimal feedback to the patient. The patient or therapist typically counts repetitions, and the assessment of contraction quality (e.g. how hard the muscle is engaging) is largely subjective.

Enhancing feedback during early exercises may improve quadriceps muscle recruitment. Prior studies have shown that adjunctive biofeedback modalities can significantly improve quadriceps activation and outcomes in early ACL rehabilitation. For example, it's demonstrated that adding electromyographic biofeedback (visual EMG signal feedback) to standard exercises in the first weeks after ACL reconstruction led to greater quadriceps EMG output and better knee extension range than exercise alone. Similarly, neuromuscular electrical stimulation (NMES) is often used alongside exercise to help activate the quadriceps, with evidence that combined NMES and exercise yields stronger quadriceps than exercise alone in the early phase post-ACL. These findings underscore the importance of maximizing muscle activation through innovative rehabilitation strategies during the vulnerable immediate postoperative period.

The Knee Extensors Activation (KEA) Device was developed to address the need for objective feedback and standardization in early quadriceps rehabilitation. The KEA device is a novel, portable tool consisting of an inflatable cushion, a hand-held air pump, an integrated pressure gauge, and a digital repetition counter. The inflatable cushion (placed under the patient's knee) provides resistance during isometric contraction, similar to a rolled towel but with adjustable pressure. The built-in pressure gauge displays the pressure inside the cushion, and is equipped with sensor markers that indicate when a full contraction (sufficient pressure threshold) is achieved. When the patient contracts the quadriceps and presses the knee down on the cushion, a pressure indicator moves; reaching the end-range sensor triggers the digital counter to register a successful repetition. The counter only increments when the pressure has risen above a preset threshold (indicating an adequate contraction) and then returns to baseline, ensuring that only correct, full-effort repetitions are counted. By providing visual feedback of pressure and an automatic rep count, the device aims to engage the patient and encourage maximal activation of the quadriceps with each contraction. In doing so, it standardizes the quad set exercise and reduces reliance on the therapist's subjective judgment of effort or on the patient's inconsistent self-monitoring.

It's hypothesized that using the KEA device in the first week after ACL reconstruction will result in greater quadriceps muscle activation compared to the conventional rolled towel method. It's further hypothesized that patients using the device will report equal or better early functional outcomes, such as reduced pain and kinesiophobia, due to potentially greater confidence in knee contraction and improved knee extension ability. This paper presents the protocol for a two-arm randomized controlled trial designed to test these hypotheses. The trial's primary objective is to compare the quadriceps muscle EMG amplitude during a maximal contraction on day 5 post-surgery between patients trained with the KEA device versus those performing standard care (towel under knee). Secondary objectives include comparing patient-reported outcomes (knee function, pain, and fear of movement) between the two groups at the end of the intervention. We anticipate that the findings will provide evidence on whether an inexpensive, feedback-enhanced device can improve early ACL rehabilitation outcomes, which could have implications for standard postoperative care.

METHODS/DESIGN Study Design and Setting This study is a single-centre, two-arm randomized controlled trial (RCT) employing parallel groups, conducted at a tertiary-care orthopedic hospital. Participants will be enrolled during their inpatient stay following ACL reconstruction. The study design aligns with SPIRIT guidelines for clinical trial protocols, and reporting will adhere to CONSORT standards. Ethical approval has been bending for review process at the Scientific Research Ethics Committee at Jouf University. All participants will provide informed consent prior to enrollment. Figure 6 illustrates the participant flow from recruitment and eligibility screening through randomization, intervention allocation (KEA device versus rolled towel), and subsequent outcome assessments performed at Day 5 postoperatively.

Participants Inclusion criteria involes Adults aged 18-45 years undergoing primary unilateral ACL reconstruction surgery are eligible for the trial. Participants must be within this age range to capture young to middle-aged adults (who are most commonly affected by ACL injuries) and to ensure a relatively homogeneous activity level. They must be undergoing a primary (first-time) ACL reconstruction on one knee (either autograft or allograft, any surgical technique) and be willing and able to participate in postoperative rehabilitation. All participants are required to provide informed consent and comply with the study procedures for the 5-day inpatient intervention and assessments.

Exclusion criteria covers patients will be excluded if they have any condition that could confound the rehabilitation or outcomes. This includes those undergoing bilateral knee surgery (simultaneous both knees, which would make the rehabilitation protocol and EMG measures incomparable), any significant neuromuscular disorder or cognitive impairment that would interfere with performing the exercises or following instructions, or any history of major lower limb surgery in the past year (aside from the current ACL surgery) that could affect muscle function (e.g. recent fractures or surgeries on the involved leg). Patients with concomitant ligament injuries requiring additional extensive repair (other than minor meniscal trim or minor collateral ligament repair) may also be excluded to maintain a relatively uniform rehabilitation course. Table 1 summarizes the inclusion and exclusion criteria.

Sample size would include a target sample of 40 participants (20 per group) has been set. A priori power analysis was performed based on detecting a difference in quadriceps EMG activation between groups at Day 5. We drew on prior research of early quadriceps facilitation: for example, Christanell et al. reported significantly greater vastus medialis EMG output in an EMG-biofeedback group versus controls at 6 weeks post-ACL,5 even with a total sample of 16 patients. Given that finding, we conservatively anticipate a moderate to large effect size for the difference in EMG amplitude at 5 days using the KEA device. Assuming a between-group difference of approximately 15-20% in normalized EMG amplitude (device vs control) with a standard deviation of \~15% (based on variability observed in similar EMG studies),3 we estimate that 16 participants per group would provide 80% power at α=0.05 (two-tailed) to detect a statistically significant difference. Our chosen sample of 20 per group (\~40 total) accounts for potential drop-outs or exclusions. The hospital where the trial is conducted performs a high volume of ACL reconstructions, facilitating recruitment of 40 patients within the planned enrollment period (approximately 6-8 months). Participants will be withdrawn from the study if they cannot complete the intervention due to medical complications or if they request to withdraw; replacements will be recruited until the target sample size is reached.

Randomization: After confirming eligibility and obtaining consent, participants will be randomly assigned to either the KEA Device group or the Towel group in a 1:1 ratio. Randomization will be performed using a computer-generated random sequence with random block sizes (to ensure concealment and balance). Allocation will be concealed in opaque sealed envelopes prepared by an independent researcher not involved in patient recruitment or treatment. On the morning of postoperative Day 1 (the day after surgery), the treating physiotherapist will open the envelope to reveal the group assignment. Due to the nature of the intervention, blinding of participants and treating therapists is not possible, patients will know whether they are using the device or a towel, and therapists must instruct accordingly. However, to minimize bias, the outcome assessor (the physiologist conducting the Day 5 EMG tests and administering questionnaires) will be blinded to group allocation. Participants will be instructed not to reveal which training method they used, and the device or towel will not be present during outcome assessments.

Intervention Protocol Both groups will receive a structured quadriceps exercise protocol starting on Postoperative Day 1 (within \~24 hours after surgery) and continuing through Day 5. This corresponds to the typical inpatient period for post-ACL recovery at our institution (patients are kept for intensive physiotherapy and monitoring during the first 5 days). The intervention consists of two supervised exercise sessions per day (morning and afternoon), for a total of 10 sessions over 5 days. Each session focuses on isometric quadriceps contractions (quadriceps setting exercises), performed as 3 sets of 10 repetitions. For each repetition, the patient is instructed to "tighten your thigh muscle and push the back of your knee down" as hard as possible, hold the contraction for 5 seconds, then relax for 5 seconds before the next repetition. After 10 repetitions, a longer rest of 1 minute is given before starting the next set. This dosage (3×10 reps, 5 s hold) is consistent with common early-phase ACL rehab protocols 6 and is intended to provide sufficient activation stimulus without fatiguing the freshly operated limb excessively. A physiotherapist will supervise all sessions to ensure proper technique and safety.

In this study, the intervention protocol varies primarily in the exercise setup and feedback mechanisms between groups. KEA Device Group participants perform quadriceps setting exercises in a long-sitting position using the patented K

• Pain intensity at rest and during exercise (VAS) [Time frame: Postoperative Day 5]
• Knee function (KOOS) [Time frame: Postoperative Day 5]
• Fear of movement (Tampa Scale of Kinesiophobia - TSK) [Time frame: Postoperative Day 5]
• Global knee function (IKDC Subjective Knee Form) [Time frame: Postoperative Day 5]