The study compares two exercise strategies in people with knee osteoarthritis. The first is aerobic exercise on a recumbent cycle ergometer, with effort controlled by the Borg scale. The second is a therapeutic exercise program with resistance, neuromuscular, mobility, and balance components. The primary objective is to determine which approach produces greater exercise induced hypoalgesia, measured by the increase in pressure pain threshold at the knee within the session across four anchor sessions during a ten week program. This is a randomized clinical trial with two parallel arms. Ninety participants, between forty five and seventy five years of age, will be allocated to one of the two groups. Allocation sequence concealment will be ensured using opaque envelopes. The outcome assessor will remain blinded to group allocation. The interventions will take place three times per week for ten weeks. Assessments will be performed at baseline and after ten weeks. Within session measurements will also be taken in weeks one, four, seven, and ten. The primary outcome is the intra session change in pressure pain threshold at the medial compartment of the knee. Secondary outcomes include exercise induced hypoalgesia in the quadriceps and trapezius, chronic adaptation of pressure pain threshold, conditioned pain modulation, pain intensity, pain self efficacy, knee related health status, functional performance, quadriceps strength, global perceived effect, and adherence. The planned sample size is forty five participants per group. The analysis will follow the intention to treat principle. The primary outcome will be compared using linear mixed models with group and time effects. Clinical outcomes at T1 will be adjusted for baseline values. Estimates, confidence intervals, and interpretation in light of minimally important differences will be reported.
Clinical diagnosis of symptomatic knee osteoarthritis for at least 3 months.
Report of knee pain for more than 3 months and average knee pain intensity ≥ 3 on the 0 to 10 Numeric Rating Scale.
Morning stiffness lasting less than 30 minutes.
Clinical signs compatible with knee osteoarthritis. crepitus, bony tenderness and absence of palpable warmth at the knee.
Signs and symptoms indicating the hip as the main source of pain.
Osteoporosis
Fibromyalgia
History of tumors or cancer
Parallel
Aerobic Exercise
Other interventionSupervised cycling on an electromagnetic recumbent stationary bicycle three times per week for ten weeks, with at least 24 hours between sessions.
Therapeutic Exercise
Other interventionIndividually supervised, land based therapeutic exercise program focusing on warm up, resisted strengthening, neuromuscular training, mobility and balance.
Exercise-induced hypoalgesia (EIH)
exercise induced hypoalgesia (EIH) of the medial compartment of the knees, measured by the change in pressure pain threshold (Δ PPT)
Exercise induced hypoalgesia of the quadriceps
Within session change in pressure pain threshold at the rectus femoris muscle, calculated as post exercise minus pre exercise values and averaged bilaterally, measured with a digital algometer and expressed in kilograms force per square centimeter.
Exercise induced hypoalgesia of the upper trapezius
Within session change in pressure pain threshold at the upper trapezius muscle descending portion, calculated as post exercise minus pre exercise values and averaged bilaterally, measured with a digital algometer and expressed in kilograms force per square centimeter.
Chronic adaptation of pressure pain threshold
Change in pressure pain threshold at the medial compartment of the knee, rectus femoris and upper trapezius between baseline and post intervention, averaged bilaterally and expressed in kilograms force per square centimeter.
Conditioned pain modulation
Change in the conditioned pain modulation effect assessed by a standardized conditioned pain modulation test, defined as the change in pressure pain threshold at the volar forearm during and after an ischemic conditioning stimulus on the contralateral arm, with pain intensity standardized around four out of ten on a numeric rating scale.
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