Analgesic and Biomechanical Effects of Intra-Articular Botulinum Toxin Type A in Chronic Knee Osteoarthritis

Impaired neuromuscular control and secondary muscle weakness in knee osteoarthritis (OA) are due to various mechanisms that pain may be the primary contributor. The purpose of this study was to investigate the two-week effects of intra-articular botulinum toxin (IA-BOTOX) on knee pain and lower-limb biomechanics. Nineteen people with knee OA (66.8±8.3 yr) were injected 2 ml BOTOX (50 units/ml) on the worse knee joints. The effect on pain was examined via Visual Analogue Scale. They walked on a level ground, and ground reaction forces (GRFs), spatiotemporal values, surface electromyography of tibialis anterior (TA), medial gastrocnemius (Gas), hamstrings (Ham), vastus lateralis (VL) and medialis (VM), and soft tissue vibration of TA and VL were collected. After IA-BOTOX injections, the knee OA increased cadences, and had a few changes in the peak values and the corresponding time of GRFs. The early activation of VM and increased amplitudes of VL and VM were observed. The knee OA significantly increased shock absorption in knee joints within 150 ms following heelstrike (HS). The present study suggested that using 50 units of IA-BOTOX analgesic and biomechanical effects were positive. Pain interruption may contribute to better neuromuscular control of lower limbs and increased shock absorption across knee joints during level-working. The future goal is to clarify the long-term effects of IA-BOTOX in the knee OA.