Botulinum neurotoxin type A improves vasti muscle balance, patellar tracking, and pain in patients with chronic patellofemoral pain

Saikat Pal, Jang Hwan Choi, Scott L. Delp, Michael Fredericson

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The purpose of this study was to determine the effects of botulinum neurotoxin type A (BoNT-A) on vastus lateralis:vastus medialis (VL:VM) muscle balance, patellar tracking, and pain in patients with chronic patellofemoral (PF) pain. We recruited 13 participants (9 females, 4 males) with recalcitrant PF pain who underwent ultrasound-guided BoNT-A injections into the distal third of the VL muscle, followed by a 6-week home exercise program to strengthen their VM muscle. We imaged the participants in a C-arm computed tomography (CT) scanner before and after the intervention. We calculated VL:VM ratios from CT images from a supine, nonweight-bearing condition. We obtained patellar tilt and bisect offset values from CT images from an upright, weight-bearing condition. We recorded functional pain scores before, immediately after, and 2–4 years after the intervention. We classified the participants into normal tracking and maltracking groups based on their patellar tilt and bisect offset values. BoNT-A with home exercise reduced VL:VM ratio (18%; p < 0.001), patellar tilt (19%; p = 0.020), and bisect offset (5%; p = 0.025). Four participants classified as maltrackers before the intervention transitioned to normal tracking after the intervention. Functional pain scores improved immediately after the intervention (13%, p < 0.001) and remained improved at 2-year follow-up (12%, p = 0.011). Statement of Clinical Significance: This study provides new evidence in support of BoNT-A for treatment of PF pain. Classification of patients under weight-bearing conditions may identify individuals who will most benefit from a BoNT-A treatment.

Original languageEnglish
Pages (from-to)962-972
Number of pages11
JournalJournal of Orthopaedic Research
Issue number5
StatePublished - May 2023

Bibliographical note

Funding Information:
The study was supported in part by a grant from Ipsen Biopharmaceuticals, Paris, France. Ipsen supplied the BoNT‐A for this study. However, the company did not play any role in study design, participant recruitment, methodology, data analysis, and writing the manuscript. Next, development of the C‐arm CT weight‐bearing imaging protocol was partly supported by the Technology Development Program of MSS (S3146559) and by the Korea Medical Device Development Fund grant funded by the Korea government (the Ministry of Science and ICT, the Ministry of Trade, Industry and Energy, the Ministry of Health & Welfare, the Ministry of Food and Drug Safety) (Project Number: KMDF_PR_20200901_0016, 9991006689). Finally, we thank Rebecca Dutton for her help with participant recruitment and data analysis.

Publisher Copyright:
© 2022 Orthopaedic Research Society. Published by Wiley Periodicals LLC.


  • anterior knee pain
  • botox
  • computed tomography
  • patellar maltracking
  • quadriceps


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