This is a randomized controlled trial examining the short- and long-term effects of mechanical nonsurgical knee joint traction on knee pain, function, and quality of life.

Knee OA symptoms are known to be impacted by increased joint loading and reduced joint space width between the articulating bones.

Objectives:

• Primary objective: Investigate the short- and long-term efficacy of adding nonsurgical knee joint distraction to standard multimodal physical therapy treatment on pain, joint function and quality of life in patients with knee OA compared with standard physical therapy treatment alone.
• Secondary objective: examine whether the efficacy of mechanical traction would differ based on the mode of application (continuous vs. intermittent traction).

Design and Subjects: A prospective, active control, three-parallel-group, investigator-blinded, randomized controlled trial. 198 subjects will be recruited and randomly assigned to one of three study groups at a 1:1:1 allocation ratio (66 participants per group): a) Standard care only, b) continuous mechanical traction plus standard care, and c) intermittent mechanical traction plus standard care.

Intervention: Participants in the standard care only group will receive 16 treatment sessions (2sessions/week) over 8 weeks, followed by 4 booster sessions (1session/2months) during the one-year period of the trial. Mechanical traction groups will receive standard care in addition to 20-minute knee traction (continuous or intermittent) using an external weight applying knee traction force.

Outcome measures: The primary outcomes are physical function and pain assessed using the Knee Injury and Osteoarthritis Outcome Score (KOOS). Secondary outcomes include the Numeric Pain Rating Scale, quality of life, Timed Up and Go, 40m fast-paced walk, and 30s chair stand tests, patient's self-perceived efficacy of treatment and patient's global assessment.

Data Analysis: Data will be analyzed using the intension-to-treat (ITT) analysis with multiple imputations. The per-protocol analysis will be carried out and reported if its findings are different from those of the primary ITT analysis. The primary analysis of the primary outcomes at two- and six-month follow-up time points will be carried out using analysis of covariance (ANCOVA) test with adjustment for a set of pre-specified baseline covariates. Secondary analysis using ANCOVA test for the primary outcomes at the 12-month time point, and secondary outcomes at all follow-up time points will also be carried out.

Inclusion Criteria:

• ≥40 years of age;
• having knee pain;
• having at least three of the following additional symptoms: a-morning stiffness ≤ 30 minutes, b-crepitation, c-bone margin tenderness, d-bony enlargement or e-no palpable warmth;
• willing to provide informed consent

Exclusion Criteria:

• rheumatoid arthritis;
• serious pathological conditions (inflammatory arthritis and malignancy); total or partial arthroplasty of the affected knee joint, or on waiting list for joint replacement surgery;
• recent surgical procedure of the lower extremities in the previous 6 months;
• uncontrolled hypertension and unstable cardiovascular problems that could subject the participant to increased risk with exercise and physical exertion;
• physical incapability to safely perform exercises, walking or stationary cycling, as in: debilitating visual defects, neurological problems, exaggerated low back pain, advanced osteoporosis, and inability to walk 10 meters without an assistive device;
• use of prescribed analgesics, corticosteroid or analgesic injection intervention for knee pain within the previous 30 days;
• lack of clear comprehension of study procedures or inability to comply with instructions;
• stated inability to attend or complete the proposed course of intervention and follow-up schedule.

Both the outcome assessors and the study statistician will be blinded to group allocation.