Objective: The objective of this study was to categorize and quantify the most common causes of joint- or leg-associated lameness by summarizing available information from cases presented to the Iowa State University Veterinary Diagnostic Laboratory (ISU VDL) between 2010 and 2015.

Materials and methods: All cases of lameness or locomotor dysfunction in 7- to 40-week-old pigs submitted to the ISU VDL between May 1, 2010 and April 30, 2015 were retrieved. After removing cases that did not meet the inclusion criteria, the remaining cases were individually reviewed and assigned a primary and secondary diagnosis.

Results: Of the 1847 cases retrieved, 464 met the inclusion criteria. The 4 most common primary diagnosis categories were Mycoplasma hyosynoviae (93 cases; 20%), metabolic bone disease (86 cases; 18.5%), infectious arthritis due to non-Mycoplasma bacterial infection (81 cases; 17.5%), and lameness with inconclusive findings (101 cases; 21.8%). There were 23.3% of the cases (108 of 464 cases) that had a secondary diagnosis with metabolic bone disease (28.7%; 31 of 108 cases) identified as the most common secondary diagnosis.

Implications: This study reinforces the importance of careful clinical examination, proper sampling, and confirming causes with appropriate diagnostic testing for accurate diagnosis of lameness.