Isometric wall squat exercises performed to volitional fatigue significantly reduced pain sensitivity in adults with knee osteoarthritis, according to findings from a randomized controlled trial conducted in Saudi Arabian outpatient physiotherapy clinics.

The study demonstrated that both single-repetition and multiple-repetition isometric wall squat protocols decreased pressure pain thresholds vs controls, though neither intervention changed clinical pain intensity. Researchers enrolled 90 patients (mean age 49 years) with chronic knee osteoarthritis diagnosed by orthopaedic physicians using radiographic evidence and clinical judgment.

Patients were stratified by sex and randomly allocated to 3 groups: isometric single-repetition wall squat (one repetition of 3 minutes or to volitional fatigue at 100° knee joint angle), isometric multiple-repetition wall squat (3 repetitions with 30-second rest intervals), or control (quiet sitting for 7 minutes). Pressure pain threshold was measured at the calf (primary site), lumbar spine, and forearm using a Wagner Digital Force Ten FDX 25 pressure algometer with 1 cm² rubber tip. Pain intensity was assessed using visual analogue scale (0 to 10).

Primary Outcomes

The isometric multiple-repetition wall squat group demonstrated higher mean pressure pain threshold ratings immediately postintervention at the calf (mean difference = 9 N/cm²), forearm (4 N/cm²), and lumbar spine (5 N/cm²) compared with control. The isometric single-repetition wall squat group reported greater increases in pressure pain threshold vs control at the calf (6 N/cm²) and lumbar spine (4 N/cm²), but not at the forearm. In a secondary analysis that compared both exercise interventions, the isometric multiple-repetition wall squat group reported higher mean change in pressure pain threshold at the forearm (5 N/cm²), but not at the calf or lumbar region compared with isometric single-repetition wall squat. Within-group analyses showed reductions in pressure pain threshold (hyperalgesia) at the calf and lumbar regions but no change at the forearm for the control group.

No group-by-time interaction effects were observed between any groups on change in pain intensity at follow-up, despite within-group reductions across all groups. Mean baseline pain intensity was 3 for isometric multiple-repetition wall squat, 3 for isometric single-repetition wall squat, and 4 for control, with postintervention values of 2, 2, and 3, respectively.

Median total hold time was 52 seconds for isometric multiple-repetition wall squat vs 23 seconds for isometric single-repetition wall squat. Linear mixed-effects modeling demonstrated a significant 3-way interaction between total hold time, time point, and group allocation on pressure pain threshold. No significant differences in expectations for pressure pain threshold or pain intensity were observed among groups.

Study Design and Methodology

This parallel-group trial employed consecutive sampling from King Abdul Aziz Hospital and King Faisal Hospital in Makkah between November 2022 and April 2023. Inclusion criteria required patients aged 18 years or older with unilateral or bilateral symptomatic knee osteoarthritis, chronic knee pain for 3 months or longer (average intensity 3/10 or greater on visual analogue scale over the past week), and self-reported ability to perform exercise.

Exclusion criteria comprised severe musculoskeletal disorders (knee varus/valgus), neuromuscular disorders (peripheral neuropathy and balance problems), uncontrolled diabetes, sensory problems, lower limb surgery, orthopaedic impairments (ligament injuries, severe deformities, or fractures within 6 months), and contraindications to exercise per American College of Sports Medicine guidelines.

Randomization was computer-generated, and allocation concealment was maintained through sequentially numbered, opaque, sealed envelopes that were prepared by a researcher who was not otherwise involved in the study. Sample size calculation used G*Power 3.1 with ANOVA repeated measures. Estimated between-group effect size was 0.35 based on pilot data (n = 21) and within-group effect sizes were 0.5 to 0.8. Previous research reported between-group effect size of 0.6 in patients with knee osteoarthritis following isometric knee extension. Analysis indicated 81 patients were required for 80% power at 2.5% significance level (Bonferroni correction); 30 patients per group were recruited to account for missing data.

Baseline characteristics showed mean body mass index of 29 kg/m², pain frequency of 5 days per week, and Western Ontario and McMaster Universities Arthritis Index score of 38. Most patients (69%) were married, had diploma degree or below (61%), were employed full-time (64%), and were nonsmokers (83%).

Statistical Analysis and Conclusions

Linear mixed-effects models included fixed effects for Group, Time, and their interaction (Group × Time), with patient ID as random effect. Models were estimated using restricted maximum likelihood. Primary analyses examined differences in change from baseline between groups and compared each intervention group to control using group-by-time interaction effects. All patients were included in intention-to-treat analysis with no missing data because outcomes were evaluated immediately following single-session intervention.

Study limitations included lack of assessor blinding, lower-than-anticipated achieved time under tension despite instructions to hold as long as possible, absence of maximum hold capacity verification, and limited generalizability to older populations.

"This is the first study to demonstrate a reduction in pain sensitivity following isometric wall squat exercise in adults with knee osteoarthritis," wrote lead study author Jamilah Zabarmawi, of the Department of Physical Therapy at King Abdulaziz Hospital, Ministry of Health, Makkah, Saudi Arabia, and colleagues.

The researchers noted the advantages that higher volumes of isometric exercise performed to volitional fatigue may have over lower volumes in inducing exercise-induced hypoalgesia were not consistently observed for all sites, including the primary site at calf muscle. "Future research is warranted to explore the roles of intensity and duration in optimizing exercise prescriptions for pain modulation," they wrote.

The trial was registered at ClinicalTrials.gov (NCT05605444).

Disclosures

This research was funded by Taif University, Taif, Saudi Arabia. One author is affiliated with Taif University, the study funder. The funder had no role in the study design, data collection, analysis or interpretation, manuscript preparation, or the decision to submit.

Source: BMJ Open