(3) presence of self-reported and/or biomechanically assessed knee instability. Self-reported knee instability was defined as at least one episode of buckling, shifting or giving way of the knee in the past 3 months, reported by the patient Biomechanically assessed knee instability was defined as the presence of muscle weakness (i.e., bodyweight-adjusted isokinetic hamstrings strength 0.80 Nm/kg for men or 0.55 Nm/kg for women) in combination with presence of (1) impaired proprioceptive accuracy (i.e., score 4.3 ) and/or (2) high passive varuse-valgus laxity (i.e., score 4.6 for men or 7.7For women).Mean scores from both legs were used; cut-off points were based on previous data
Exclusion criteria were (1) other forms of arthritis than OA (e.g., crystal arthropathy, septic arthritis, spondyloarthropathy) identified by radiography and/or blood- and urine samples, (2) presence ofcomorbidity resulting in severe activitylimitations, (3) total knee arthroplasty (TKA) or TKA in near future, (4) severe knee pain (i.e., numeric rating scale (NRS) >8), (5) insufficient comprehension of Dutch language, (6) inability to be scheduled for therapy, and (7) unwillingness to give informed consent.