Introduction: In this study, the efficacy of platelet rich plasma (PRP) in the treatment of formaldehyde (FA) induced arthritis was evaluated. Material and Methods: Forty two adult male albino rats were divided into three groups. Group I (control group): eighteen rats were divided into I-a, I-b, and I-c subgroups. Group II (arthritic group): twelve rats were subjected to intra-articular injection with single dose of 0.02 ml of 5% FA in the right knee and were further subdivided into II-a and II-b subgroups. Group III (arthritic group treated with PRP): twelve rats were subjected to induced arthritis as in group II. Then they were subjected to intra-articular injection with single dose of 0.3 ml of PRP in the same right knee and were further subdivided into III-a and III-b subgroups. Results: After sacrifice, the knee joints were fixed, decalcified, and processed for paraffin sections. Different stains were applied and immunohistochemical staining for Caspase-3 enzyme was done. Sections were examined by light microscope. The arthritic groups revealed irregular articular surface and bone eburnation. There was apparent hypocellularity and disorganization of the chondrocytes. Osteoclasts and osteoblasts invaded the osteochondral junction. The synovial membrane showed deposition of thick collagen bundles with inflammatory cell infiltrate and numerous blood vessels. Caspase-3 immunoreactivity was apparent in many chondrocytes. All these changes were ameliorated in group III-a. Many of these changes were seen in Group III-b. The morphometric results and statistical analysis confirmed the histological findings. Conclusion: It was concluded that intra-articular injection of PRP demonstrated transient effective role on articular cartilage healing.