Efficacy of intra-articular botulinum toxin type A in painful knee osteoarthritis: a pilot study.
OBJECTIVE
To evaluate the efficacy and safety of botulinum toxin type A (BoNT-A) injected intra-articularly in 60 subjects with moderate pain and functional impairment secondary to knee osteoarthritis. The study investigators hypothesized that intra-articular BoNT-A would result in statistically significant improvements in pain and function at 8 weeks.


METHODS
Double-blind, randomized, single tertiary care academic medical center trial with 6-month follow-up.


METHODS
Sixty patients aged 40 years or older with painful osteoarthritis of the knee who had failed physical therapy, medications, and/or injection therapy presenting to the musculoskeletal or orthopedic outpatient clinics at a large tertiary care medical institution. All 60 patients completed 8-week follow-up, but only 32 patients completed the 26-week follow-up.


METHODS
Subjects were randomized to receive a single injection of corticosteroid, low-dose BoNT-A (100 units), or high-dose BoNT-A (200 units). Outcome measures were compared at baseline, 4, 8, 12, and 26 weeks after injection.


METHODS
The primary outcome measure was pain visual analog scale (VAS) at 8 weeks. Secondary outcome measures included Western Ontario McMaster Arthritis Index, Short Form-36 scores, patient global assessment, 40-meter timed walk, and adverse effects.


RESULTS
The primary end point was pain VAS score at 8 weeks, which decreased within each group but only reached statistical significance in the low-dose BoNT-A group. In the intra-articular corticosteroid group, VAS decreased from 6.4 +/- 1.8 to 5.4 +/- 2.3 (P = .15); for low-dose BoNT-A, from 6.6. +/- 1.9 to 4.5 +/- 2.2 (P = .01); and for high-dose BoNT-A, from 6.6 +/- 1.4 to 5.9 +/- 2.4 (P = .15). All groups showed statistically significant improvements in Western Ontario McMaster Arthritis Index scores (pain, stiffness, function) at 8 weeks. No serious adverse events were noted in any group.


CONCLUSIONS
This pilot study supports a possible role for BoNT-A as a treatment option for symptomatic knee osteoarthritis; however, larger double-blind randomized studies are needed to determine whether BoNT-A is more effective than placebo in this patient population.
Boon
Andrea J
AJ
Department of Physical Medicine, Mayo Clinic College of Medicine, Rochester, MN, USA. boon.andrea@mayo.edu
Smith
Jay
J
Dahm
Diane L
DL
Sorenson
Eric J
EJ
Larson
Dirk R
DR
Fitz-Gibbon
Patrick D
PD
Dykstra
Dennis D
DD
Singh
Jasvinder A
JA
D000368:Aged; D019274:Botulinum Toxins, Type A / Q000008:administration & dosage*; D015331:Cohort Studies; D004311:Double-Blind Method; D005260:Female; D006801:Humans; D007270:Injections, Intra-Articular; D008297:Male; D008875:Middle Aged; D009465:Neuromuscular Agents / Q000008:administration & dosage*; D020370:Osteoarthritis, Knee / Q000150:complications* / Q000188:drug therapy* / Q000503:physiopathology; D010147:Pain Measurement; D010865:Pilot Projects; D020127:Recovery of Function; D016896:Treatment Outcome
D009465:Neuromuscular Agents; D019274:Botulinum Toxins, Type A