Intra-articular injections for the treatment of knee pain due to osteoarthritis are performed when conservative therapies have failed. The intra-articular injection of lidocaine may be an effective treatment modality due to its neuronal membrane-stabilizing effect and long-lasting anti-inflammatory action. In this study, we compared the efficacy of intra-articular 0.5% lidocaine versus saline injection on pain, stiffness and physical function in patients with osteoarthritis.

Patients with osteoarthritis were randomly allocated to two groups. Group I (n=26) received 7mL 0.5% lidocaine and group II (n=26) received 7mL saline into the painful knee for a series of three injections spaced by 1 week intervals under ultrasound guidance. Knee pain was measured with a numeric rating score (NRS) at baseline and 3 months after the 3rd injection. WOMAC scales, including pain (WOMAC-P), stiffness (WOMAC-S) and physical function (WOMAC-F), were assessed and recorded at baseline, 30minutes after the 1st injection, immediately prior to the 2nd and 3rd injections and 3 months after the 3rd injection.

Demographic data were comparable between groups. The NRS after 3 months was significantly lower in group I (P=0.001). The WOMAC-P, immediately prior to the 3rd injection and 3 months afterwards, was significantly lower in group I (P=0.006, P=0.001, respectively). The WOMAC-S was improved prior to the 3rd injection and sustained until 3 months in group I (P=0.035, P=0.004, respectively). The WOMAC-F was improved after the 1st injection and sustained until 3 months in group I (P=0.002, P<0.0001 and P<0.0001, respectively).

Intra-articular 0.5% lidocaine injection under ultrasound guidance has a potential role in the management of chronic knee pain due to osteoarthritis for a 3-month period.