Working Diagnosis:
Synovial osteochondromatosis

Treatment:
Discussion regarding symptomatic treatment with oral NSAIDs or intra-articular steroid ensued. Due to the patient's previous treatment failures, hyaluronic acid injections were not recommended. It was explained that some of the pain may be due to mechanical obstruction within the joint by the loose body. Removal of loose body was recommended for treatment. It was also explained that even with excision, osteochondromatosis can recur and there may be residual pain due to underlying osteoarthritis.

Outcome:
The patient underwent left knee arthroscopy, debridement and extensive removal of osteocartilaginous loose bodies (multiple from 5-8 mm to 1.5 - 2 cm in size). Partial synovectomy was also performed. (Case Photo 3)

The patient experienced complete resolution of symptoms one week post-operation.

Author's Comments:
Synovial Osteochondromatosis

Definition
-Rare benign condition involving synovial lining of joints, synovial sheaths, and bursae
-Metaplastic process of synovium causes conversion to cartilage, which eventually becomes detached from joint lining to become a loose body
-Exact reasoning for metaplasia is not clearly understood

Epidemiology
-Most common in third to fifth decades of life
-Affects men more than women by 2:1 ratio

Presentation
-Usually involves a single large joint (knee, hip, shoulder)
-Less common involvement of smaller joints (MTP, MCP, tibio-fibular)
-Sensation of floating objects in knee
-Pain, swelling, restriction of movement, mechanical symptoms

Editor's Comments:
In current practice, the literature suggests that arthroscopic removal of loose bodies for mechanical symptoms is the best surgical treatment. This strategy minimizes postoperative stiffness associated with open procedures and successfully accomplishes synovectomy and loose body removal. Longer follow-up has validated the success described in early arthroscopic reports. Arthroscopic treatment in other joint is also supported by current evidence

References:
Jeffreys, T. (1967). Synovial Osteochondromatosis. The Journal of Bone and Joint Surgery, 530-534.

Milgram, J. (1977). Synovial osteochondromatosis: a histopathological study of thirty cases.
Journal of Bone and Joint Surgery, 792-801.

Mackenzie, H., Gulati, V., & Tross, S. (2010). A rare case of a swollen knee due to disseminated synovial chondromatosis: a case report. Journal of Medical Case Reports. http://dx.doi.org/10.1186/1752-1947-4-113

Rangoako, ST, Raubenheimer, EJ, & Mafeelane, K. (2015). Synovial chondromatosis: A review of the literature and report of two cases. SA Orthopaedic Journal, 14(1), 48-51. Retrieved June 14, 2016, from http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S1681-150X2015000100009&lng=en&tlng=en.

McKean, J. (2014, April 7). Synovial Chondromatosis. Retrieved June 14, 2016, from Ortho Bullets
website: http://www.orthobullets.com/pathology/8051/synovial-chondromatosis

Acknowledgments:
Special thanks to the patient and her family for allowing presentation of this case for educational purposes

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