Introduction: Diffuse pigmented villo-nodular synovitis (DPVNS) of the knee remains a difficult tumor to eradicate. We report our experience with a combined posterior and open synovectomy technique.

Method: A single surgeon operated on 40 patients averaging 35 years old (14 to 68 years). The patients were placed into one of three groups: group I received surgery alone (five patients), group II had surgery and intra-articular radiation synovectomy using Dysprosium-165 (165Dy) (30 patients), and group III had surgery and external beam radiation (5 patients). The adjuvant radiation was performed three months postoperatively. MRI evaluation was used preoperatively and post-operatively.

Results: The average combined Knee Society Scores and range of motion improved. Thirty-seven patients (92.5%) had a good or excellent results; two (5%) had a fair result; and one (2.5%) had a poor result. There were seven recurrences (17.5%). None occurred in group I; five occurred in group II (12.5%); and two occurred in group III (5%).

Discussion & Conclusions: This technique allowed excellent visualisation and removal of intra- and extra-articular DPVNS tissue with excellent functional results and few recurrences documented by MRI. Adjuvant intra-articular radiotherapy may be beneficial for small foci of residual disease but complete resection of all DPVNS tissue was the key to prevent recurrence. External beam radiation did not prevent recurrence and possibly predisposed patients to pain and less improvement in knee flexion. Extensive pre-operative degenerative joint disease predisposes patients to continued pain.