A patient was seen at a physical therapy clinic of Comunidad de Madrid. The physical therapy sessions were conducted by an experienced physical therapist with 11 years of clinical practice, starting 5 days post-injury. This case report adhered to the CARE guidelines (Riley et al., 2017). The patient was a 33-year-old male recreative soccer player who described the feeling of being “stabbed” in his thigh while performing sprint training. Earlier that day, he had a feeling of general tiredness. The injury occurred during a running training session, not while playing soccer. Due to a lack of time, the warm-up on the day of the injury consisted only of jogging for 5 min. During the second set of 30-m sprints, while attempting to run at maximum intensity, the patient felt a severe pain in the inner part of his quadriceps and had to stop immediately. The sensation of functional impotence was immediate, and he was barely able to walk. He described his pain as deep, localized, and exacerbated with walking. Using an 11-point numeric pain rating scale, with 0 as no pain and 10 as maximum tolerable pain, the pain was rated 7–8/10.

The patient’s medical history included a previous muscle strain in the same location 3 years earlier. The injury affected his right thigh, which was also his dominant limb, which is essential for strength evaluation. He had been playing soccer recreationally for over 10 years, participating in both weekly matches and training sessions. His regular physical activity included running 10 km, swimming 1,500 m, and strength training for 2 hours each week. He described his pre-injury health status as “very good” and felt he was in an optimal physical condition. This detailed background provides a comprehensive understanding of his fitness level and activity patterns prior to the injury. The patient’s primary goal was to return to recreational soccer.

The initial physical examination and the follow-up (Figure 1) was performed by an 11-year experienced physical therapist. The initial physical examination was performed 5 days post-injury to allow the acute symptoms to stabilize and to obtain a clearer assessment of the injury. Early examination might have been confounded by acute inflammation and pain, potentially leading to an inaccurate diagnosis. This was done in order to rule out other pathologies that cause anterior thigh pain, such as upper-lumbar radiculopathy, femoral neuropathy, and iliopsoas or sartorius muscle injury. The severity of the rectus femoris strain was determined to be grade 1, as confirmed by ultrasonography. This classification aligns with previous research on muscle injuries (Hamilton et al., 2015; Palermi et al., 2021).

Figure 2 shows the ultrasonographic image of the rectus femoris 1 week post-injury, indicating the location and extent of the strain. The injury was localized at the mid-belly of the rectus femoris muscle, with no signs of tendon involvement. A final ultrasonographic examination was not performed as the patient had clinically recovered, meeting all functional criteria for returning to play without any reported symptoms.

During the physical examinations, pain intensity was consistently evaluated using the visual analog scale (VAS). In phase 1, femoral nerve tension was assessed with the femoral slump test, and active range of motion (AROM) of hip flexion with knee extension was measured through the active straight leg raise test (ASLR) (Liebenson et al., 2009). Additionally, AROM of hip extension with the knee extended in supine decubitus, AROM of knee flexion in prone decubitus, and passive range of motion (PROM) of knee flexion were evaluated (Liebenson et al., 2009). Hip flexor strength at 90 degrees of hip flexion in the supine position and knee extensor strength in the seated position were measured using a digital inclinometer and a hand-held dynamometer (ActivForce 2, USA) (Thorborg et al., 2013). In phase 2, rectus femoris flexibility was assessed by AROM of hip extension, AROM of knee flexion, and PROM of knee flexion, while hamstring flexibility was evaluated using the ASLR test. Hip flexor strength was measured at 90° of hip flexion and at 0° of hip flexion with the knee extended (long lever arm), and hip extensor strength was evaluated in the prone position with knee flexion. In the final phase (phase 3), the same parameters—rectus femoris flexibility, hamstring flexibility, and hip flexor and extensor strength—were reassessed to determine the patient’s readiness to return to play.

The contralateral limb was assessed during the phases 1, 2, and 3 to compare rectus femoris flexibility, hamstring flexibility, and hip flexor and extensor strength between both limbs. The criteria to progress between the phases are described in Figure 1. The physical examination was performed every week to assess all risk factors.

After the initial clinical examination (5 days post-injury), the recreational soccer player began the rehabilitation program that was controlled by the same physical therapist. The rehabilitation program (Table 1) was adapted from another protocol for hamstring strain injuries, previously published by Mendiguchia et al. (2017) Each week, the patient performed four sessions of rehabilitation and engaged in swimming to maintain cardiorespiratory fitness, which complemented the rehabilitation program by providing low-impact aerobic conditioning. During phase 1 of the rehabilitation program, the patient performed all the exercises (Table 1) adapted according to muscle flexibility, rectus femoris strength, and gluteal strength four times a week (Figure 3). During phases 2 and 3, the rectus femoris flexibility, strength, and gluteal strength exercises were modified, improving the difficulty of the exercises by adding more resistance or with greater multi-joint involvement. The patient was instructed to perform the exercises at an intensity of 8 (very heavy) on the rate of perceived exertion (RPE) scale throughout all three phases of the rehabilitation program.

The patient followed a 3-day block periodization, where day 1 included running drills and lumbopelvic control, day 2 focused on flexibility and strength training, and day 3 focused on flexibility and lumbopelvic control. During phase 3, the patient performed at least two such treatment blocks per week. Only mild discomfort (VAS ≤ 3) was allowed when performing the exercises. Sets and repetitions of strength training were performed according to previous studies (Mendiguchia et al., 2017).

Outcomes from the patient can be seen in Table 2. Final evaluations were performed by the same therapist who performed the initial evaluations and oversaw each treatment session. Following a program based on specific training of the rectus femoris, lumbopelvic stabilization, mobility exercises, and running technique exercises, the patient improved functionally and returned to play soccer 6 weeks after the injury without pain.

The patient reported pain when performing his daily tasks only during the first 2 weeks after the injury and was able to run at 10 km/h for 10 min 25 days after the injury. The criteria to return to run were having rectus femoris and hamstrings flexibility and a hip flexor and extensor strength deficit of <30% compared to the contralateral (Mendiguchia et al., 2017) (Figure 1).

Improvements were observed in the right knee flexion range of motion and the right hip flexor strength throughout the 6 weeks of treatment and then in the 12 weeks post-injury follow-up. In addition, the hip and knee extensor strength of both limbs improved throughout the 6 weeks of treatment and was maintained in the 12 weeks post-injury follow-up. Moreover, at 12 weeks post-injury, clinical deficits between limbs in hip flexion strength at 90° of hip flexion persisted. At discharge 6 weeks after the injury, the patient achieved his goal of returning to play recreational soccer. Moreover, the patient passed the criteria of each phase at week 2 for phase 1, at week 4 for phase 2, and at week 6 for phase 3 (return to sport).

The patient was grateful for being able to return to play within a reasonable period of time without having recurrences of his injury.

The patient provided verbal consent to publish his data. As only one patient was described and standard-of-care clinical services were provided, the medical center required no formal Institution Review Board approval.