The primary aim of this study is to investigate whether low-dose radiotherapy is an effective treatment to reduce the pain of knee osteoarthritis. A secondary aim is to determine whether patients experience any more measurable side effects than those receiving sham treatments.

This single center, single-blinded, sham-controlled randomized controlled trial will compare low dose radiation therapy and sham radiation therapy for knee osteoarthritis. Participants with symptomatic knee OA based on clinical and radiographic criteria will be randomized 1:1 to receive 0.5 Gy LDRT over 2 weeks ideally on a Monday-Wednesday-Friday three times each week for two weeks treatment course for a total of 3 Gray or identical sham treatment (an identical procedure without the radiation). Non-responders to the initial Low-Dose Radiotherapy (LDRT)/sham treatment will receive a second treatment course of 0.5 Gy Low-Dose Radiotherapy (LDRT) or sham repeat treatment course over 2 weeks x 6 depending on their randomization (treatment arm participants receiving a second treatment course and sham arm participants receiving a second course of identical sham treatments without radiation). Intermittent and Constant Osteoarthritis Pain (ICOAP) outcome scales will be emailed to all participants for completion at baseline and weekly for six months. The study will thus terminate after all participants have completed 6 months of time in the study.

Inclusion Criteria:

• • patient's primary care provider is at Mayo Clinic in Rochester, MN

  • age 50-100 years

  • ICOAP pain scale A1 at least moderate intensity or B6 at least moderate intensity

  • diagnosed with primary knee OA ICD-10 codes M17.x

    o You have not had recurrent episodes of sudden onset of warmth, redness, or swelling of the affected knee

  • physical exam findings of medial or lateral joint line tenderness on palpation that is in the same location as the knee pain.

  • absence of primary knee pain in the pes anserine or hamstring or gastrocnemius, quadriceps, or patellar tendons on exam.

  • radiographic Kellgren-Lawrence grade 2-3 on 4-view knee x-rays taken within the last year ability to complete surveys electronically by email

Exclusion Criteria:

• • Kellgren-Lawrence grade 1 or 4

  • pregnancy or women 54 years and younger with potential for pregnancy (if they or their partner have not had tubal ligation, hysterectomy, or vasectomy)
  • history of ipsilateral intraarticular knee surgery
  • use of injected corticosteroids within 3 months or hyaluronans within 6 months or within 1 month if there was no sustained improvement post-injection of either corticosteroid or hyaluronan.
  • history of trauma to this knee in the last year that clearly caused the pain now present
  • history of RA, gout, pseudogout, hemarthroses (eg, hemophilic arthropathy) or other inflammatory arthritis involving this knee
  • history of symptomatic hip OA
  • history of psychosis, personality disorder, uncontrolled affective disorder
  • history of fibromyalgia
  • malignancy requiring active treatment current regular use of opiate analgesics, PRP, or acupuncture for the knees