Topical capsaicin has shown some efficacy in treating pain associated with knee OA.57 One meta-analysis of RCTs concluded that topical NSAIDs and capsaicin may be equally efficacious for OA-associated pain relief, although none of the RCTs directly compared the two.58 The major limitation of capsaicin is a patient-reported mild-to-moderate burning sensation with application that may decrease compliance.
Emerging treatments: IA PRP & extended-release IA triamcinolone acetonide
IA platelet-rich plasma (PRP) has been investigated for efficacy in treating knee OA. PRP is thought to decrease inflammation in the joint, although its exact mechanism remains unknown.59 Multiple studies have shown some benefit of PRP in reducing pain and improving function in individuals with knee OA, but nearly all of these studies have failed to show a clear benefit of PRP over HA injections.59-63 Additionally, the authors of most of these studies mention a high risk of bias. PRP therapy is expensive and generally is not covered by insurance companies, which precludes its use for many people.
Extended-release (ER) IA triamcinolone acetonide (Zilretta) has shown some superiority to standard IA triamcinolone acetonide in both degree and duration of pain relief for knee OA.64-66 The ER version tolerability did not differ from placebo and also showed prolonged synovial presence, lower systemic absorption, and lower blood glucose elevations compared with standard triamcinolone.64-66
Surgical intervention: A last resort
Select patients with severe pain and disability from knee OA that is refractory to conservative management options should be referred for consideration of knee arthroplasty. Age, weight, OA location, and degree of OA are all considered with respect to knee arthroplasty timing and technique.
There is good evidence that arthroscopy with debridement, on the other hand, is no more effective than conservative management.67
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