M99.9: Biomechanical lesion, unspecified

Biomechanical lesion, unspecified (ICD-10 code M99.9), refers to a disorder that affects the body's mechanical structure or function without a specific cause identified. This condition distorts the natural movement or functioning of a part of the body, typically involving the musculoskeletal system—the body's system of muscles, bones, and joints. Common symptoms may vary widely depending on the area affected but may include discomfort, pain, swelling, and limited mobility or flexibility. The progression of the disease might also differ, with some individuals witnessing a slow increase in symptoms over time while others might experience sudden onset. Importantly, this condition should not be confused with injuries resulting from external trauma. "Unspecified" refers to cases where the exact cause or location of the biomechanical problem is not determined.