Using Pressure Detecting Insoles to Reduce Knee Loading

This is a randomized longitudinal proof-of-concept study. After a telephone prescreening, an in-person visit will screen for inclusion and exclusion criteria, requiring a clinical and radiographic assessment. A total of 40 subjects with symptomatic and radiographic medial knee OA will be enrolled in the study after obtaining informed consent. A total of three study visits will occur at the following time points: baseline, 3 weeks, and 6 weeks. At all three visits, the following outcome variables will be acquired: (1) joint loads during gait using 3D motion analysis and (2) knee symptoms, stiffness, pain, daily function, recreational function, and quality of life using the validated questionnaires. At the baseline visit, every participant will receive a standardized shoe and a pressure-detecting shoe insole. Randomly assigned to one of two groups, participants assigned to group A (n=25) will train for 3 weeks in the mobility shoe with active pressure-based feedback from the shoe insole, and group B (n=15) will train for three weeks in the mobility shoe with a passive shoe insole. All subjects will be encouraged to wear the study shoes containing the shoe insoles as their primary form of footwear and for a minimum of 6 hours/day, 6 days/week. They will be given a diary to record the daily time spent wearing the shoe/insole, daily analgesic history, and adverse events. These diaries will be reviewed at the 3 and 6 week study visits. After completing the third visit, subjects will have completed the study.

Inclusion criteria

• Able and willing to give informed consent and comply with the study protocol.
• Symptomatic OA of the knee greater than 3 months, as defined by the American College of Rheumatology's Clinical Criteria for Classification and Reporting of OA of the Knee. If symptoms are bilateral, then the knee identified as more symptomatic will serve as the index knee.
• Ambulatory knee pain, defined as the presence of greater than 30 mm of pain while walking on a flat surface (corresponding to question 1 of the visual analog format of the WOMAC).
• Radiographic OA of the study knee of grade 2 or 3, as defined by the modified Kellgren and Lawrence (K-L) grading scale.
• Medial compartment OA, defined as either qualitative joint space narrowing of ≥ 1or the presence of medial bone cyst, sclerosis, or osteophyte.
• Able to walk at least 10 minutes without a break.
• Age of 40 years or older

Exclusion criteria

• Unwillingness to wear study shoes for at least 6 hours/day for 6 days of the week
• Knee flexion contracture of > 15 degrees or inability to ambulate without assistance.
• Presence of clinical OA of the ankle or hip or ankle/hip pain>10 mm (WOMAC).
• Predominant lateral compartment OA, defined as narrowing of the lateral joint space in excess of the narrowing of the medial joint space in either knee.
• Concurrent systemic inflammatory arthropathy
• Prior knee or hip arthroplasty, or surgical arthroscopy within the previous 3 months.
• Intrinsic foot disease: hallux rigidus, hallux abducto-valgus, metatarsalgia, plantar fasciitis, peripheral neuropathy, or any foot condition that may be exacerbated particular footwear.
• Intra-articular knee injection: steroids within 6 wks, hyaluronan derivatives within 4 mos.
• Body mass index greater than 38.