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Objective To investigate the efficacy of two volumes of acute isometric wall squat exercise on pain sensitivity (primary outcome: pressure pain threshold (PPT)) and intensity (secondary outcome) in adults with knee osteoarthritis.Design A parallel-group randomised controlled trial.Setting Outpatient physiotherapy clinics at hospitals in Saudi Arabia.Participants Participants (n = 90; mean (SD) age 49.0 (13.0) years) with chronic knee osteoarthritis, diagnosed by a specialist orthopaedic physician using radiographic evidence and clinical judgement, were recruited via two tertiary hospitals in Saudi Arabia.Intervention Participants were stratified by sex and randomly allocated to one of three groups: isometric single-repetition wall-squat (ISO-SR; one repetition of a 3-min wall squat or to volitional fatigue at a 100° knee joint angle), isometric multiple-repetition wall-squat (ISO-MR; three repetitions of the same intervention) and control (quiet sitting for 7 min).Primary and secondary outcome measures PPT was measured at the calf (primary site of interest), lumbar spine and forearm using a pressure algometer. Pain intensity was assessed using a visual analogue scale. Primary analyses compared changes between intervention and control groups. All participants were included in the ITT analysis.Results The ISO-MR group had higher mean PPT ratings immediately postintervention in the calf (mean difference=9.4 (95% CI 5.6 to 13.2), p<0.001), forearm (4.0 (95% CI 1.2 to 6.9), p=0.006) and lumbar spine (5.4 (95% CI 2.4 to 8.4), p<0.001), compared with control. The ISO-SR group reported a greater increase in PPT when compared with control at the calf (5.8 (95% CI 2.0 to 9.6), p=0.003) and lumbar spine (3.7 (95% CI 0.7 to 6.8), p=0.015). There were no differences in clinical pain intensity between the groups.Conclusions Both the ISO-SR and ISO-MR exercises to volitional fatigue reduced pain sensitivity in patients with knee osteoarthritis. Neither exercise volume changed clinical pain intensity.Trial registration number ClinicalTrials.gov registry (ID: NCT05605444).