BACKGROUND: Force perception as a contributor to the neuromuscular control of the knee joint may be altered after anterior cruciate ligament (ACL) injury. OBJECTIVE: This study aimed to compare the force perception accuracy in the knee joints of patients with ACL injury and healthy subjects. METHODS: Twenty-six patients with ACL injury and 26 healthy subjects participated in this case-control study. Participants were asked to produce 50% of the maximum voluntary isometric contraction of the knee muscles as a target force and reproduce it in their limbs in flexion and extension directions. RESULTS: There were significant interactions between group and condition as well as group, condition, and limb in the force perception error respectively (P< 0.05). The highest amount of error was seen in the contralateral limb of the ACL injury group when the reference force was produced in the injured limb (P< 0.05). CONCLUSION: The findings revealed that the force perception accuracy in the knee flexor/extensor muscles of individuals with ACL injury is impaired. Moreover, error is most evident when the patient produces force in the injured limb and replicates it in the uninjured limb in both flexion and extension directions. Therefore, the rehabilitation programs should encompass neuromuscular training in both quadriceps and hamstrings after ACL injury.

[Purpose] The aim of this study was to determine the reliability of a newly designed dynamometric device for use in frequent force producing/reproducing tasks on the knee joint. [Subjects and Methods] In this cross-sectional study (Development & Reliability), 30 young healthy males and females (age 23.4 ± 2.48 years) were selected among students of Tabriz University of Medical Sciences by simple randomized selection. The study instrument was designed to measure any isometric contraction force exerted by the knee joint flexor/extensor muscles, known as the ipsilateral and contralateral methods. Participant knees were fixed in 60° flexion, and each participant completed the entire set of measurements twice, 72 hours apart. [Results] The findings showed a good intraclass correlation coefficient of 0.73 to 0.81 for all muscle groups. The standard error of measurement and smallest detectable difference for flexor muscle groups were 0.37 and 1.02, respectively, while the values increased to standard error of measurement=0.38 and smallest detectable difference=1.05 for extensor muscle groups. [Conclusion] The device designed could quantify the forces producing/reproducing tasks on the knee joint with a high rate of reliability, and can probably be applied for outcome measurements in proprioceptive assessment of the knee joint.

Objectives: Chronic low back pain (CLBP), along with physical limitations that affect the quality of life, is one of the most important problems in the health community. The pain causes a wide range of structural, functional, and neurological changes in the brain. However, these changes have not been well studied, as brain changes in other chronic pains. This study aimed to evaluate the changes in the electroencephalogram (EEG) of patients with nonspecific CLBP, and also to evaluate the effects of interferential current (IFC), as one of the common treatment methods in these patients, on the EEG. Methods: This randomized control trial was performed in the Physiotherapy Clinic of Rehabilitation Faculty of Tabriz University of Medical Sciences from July 2021 to February 2022. A total of 20 patients with nonspecific CLBP and 20 healthy individuals participated in this study. Healthy subjects were in the control group, and the patients were randomly divided into two groups: intervention and placebo. Participants’ EEG and pain intensity were recorded before and after one session of IFC. Results: The results of statistical analyses to compare the EEG of patients and healthy individuals did not show a significant difference between the two groups. The results of statistical tests to evaluate the effects of IFC on participants’ EEG showed a significant increase in alpha frequency in all three groups. In addition, a significant increase in theta frequency was recorded in the placebo group, and an increase in the beta frequency in the intervention group. Pain intensity showed a significant decrease only in the intervention group. Discussion: The results of this study suggest that changes in EEG in patients with low back pain may be related to the severity of pain and neurological involvement. In addition, the increased power of EEG following the application of IFC may be due to sensory stimulation of the skin surface.

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