Botox for Non-surgical Lateral Release in Patellofemoral Pain

The purpose of this study is to determine whether the use of botulinum toxin A injected into the lateral thigh muscle improves knee function and reduces knee pain secondary to patellofemoral syndrome. The study hypothesis is that botulinum toxin + specific exercises will be superior to specific exercises alone in improving knee function and reducing knee pain in individuals with patellofemoral syndrome.

Patellofemoral pain syndrome is a leading cause of knee pain in persons under 45 and is particularly common in women. The prevailing theory for the etiology of patellofemoral pain is an imbalance in force or timing of the pull of the knee extensor muscles on the patella resulting in improper tracking of the patella in the femoral grove. Specifically, the vastus medialis is thought to be ineffective in overcoming the lateral pull of the vastus lateralis. When exercises designed to focus on improving strength and timing of activation of the vastus medialis fail, surgical release of part of the attachment of the vastus lateralis to the patella is considered. Botulinum toxin temporarily blocks acetylcholine release from motor neurons and is used clinically to produce muscle relaxation. Subjects with patellofemoral syndrome will be recruited into the study. Half of the subjects will be given a placebo injection while the other half will be given an injection of Botox (Botulinum Toxin A, Allergen) into the vastus lateralis muscle. Group assignment will be randomized and a double blind protocol used. Prior to injection, the subject will record their level of knee pain, fill out several knee function questionnaires, and have the strength and endurance of their knee extensor muscles tested. All subjects will be given an exercise program designed to target strengthening of the medial thigh muscles as well as stretching of lateral structures. At 4, 6 and 12 weeks knee pain and knee function will again be assessed.

Injection of 100 units Botox (Botulinum toxin type A) into the Vastus Lateralis of the study leg + 12 weeks of exercise for patellofemoral pain

Injection of 2 cc placebo containing 0.1cc sodium bicarbonate 8.4% (1meq/cc), 0.9cc normal saline and 1 cc of lidocaine into the vastus lateralis of the study leg followed by 12 weeks of exercise for patellofemoral pain syndrome

Visual Analog Scale pain rating (VAS). 10 cm line with anchors at 0 (no pain) and 10 cm (worst imaginable pain). Scores are in cm (0 - 10) 0 no pain, higher values greater pain. Results given are for change at 12 weeks compared to baseline (week 12 score - baseline score)

Anterior Knee Pain Scale: a 13-item questionnaire; a TOTAL score of 0 = severe disability; a score of 100 = no pain or disability. (items are scored 0-5 or 0-10). Change scores at 12 wks are reported. Inverted so positive values reflect improvement. Included items: difficulty with: weight bearing, walking, stairs, squat, run, jump, prolonged sitting; presence of limp, swelling, patellar subluxation, atrophy of thigh, reduced knee flexion. Reference: Kujala et al: Scoring of Patellofemoral Disorders. J Arthroscopic Rel Surg, 9(2)159-163, 1993

The Functional Index Questionnaire (FIQ) is a self report functional rating scale. Individuals rate eight-activities. Each activity is rated from 0 - 2 with ) being unable to perform the activity and 2 being able to perform the activity without difficulty. The total score is summed for a final score of 0 - 16. 0 indicates that the individual is ubable to perform any of the tasks, 16 indicates that the subject is able to perform all tasks without difficulty. The eight items include: walking (1 block and 1 mile), climbing stairs (2 flights and 4 flights), squatting, kneeling, prolonged sitting, and running

The lower extremity functional scale (LEFS) is a self report questionnaire. Subjects rate 19 items related to general activities that require the lower extremities on a scale of 0 - 4. 0 = extreme difficulty or unable to perform the activity, 4 = No difficulty performing the activity. The total of all rankings are summed and divided by the maximum score (76). The score is reported as a percentage. 100% = no difficulty in performing any of the tasks. 0% = extreme difficulty or unable to perform all of the tasks.

Inclusion Criteria: retropatellar knee pain pain with two of: prolonged sitting, climbing stairs, squatting, running, kneeling, hopping, jumping pain with patellar palpation symptoms minimum 1 month Visual Analog Scale for pain (VAS) usual pain 4 of 10 on VAS [0-10 scale, anchors 0 = no pain, 10 = worst pain imaginable] Exclusion Criteria: history knee surgery history patellar dislocation clinical evidence of meniscal lesion, ligamentous instability, traction apophysitis around the patellofemoral complex, patellar tendon pathology, chondral damage, osteoarthrosis, spinal referred pain

Singer BJ, Silbert PL, Dunne JW, Song S, Singer KP. An open label pilot investigation of the efficacy of Botulinum toxin type A [Dysport] injection in the rehabilitation of chronic anterior knee pain. Disabil Rehabil. 2006 Jun 15;28(11):707-13. doi: 10.1080/09638280500301477.

Crossley K, Bennell K, Green S, McConnell J. A systematic review of physical interventions for patellofemoral pain syndrome. Clin J Sport Med. 2001 Apr;11(2):103-10. doi: 10.1097/00042752-200104000-00007.

Crossley KM, Bennell KL, Cowan SM, Green S. Analysis of outcome measures for persons with patellofemoral pain: which are reliable and valid? Arch Phys Med Rehabil. 2004 May;85(5):815-22. doi: 10.1016/s0003-9993(03)00613-0.