Fibrotic myopathy is a chronic, progressive, idiopathic, degenerative disorder affecting the semitendinosus, gracilis, quadriceps, infraspinatus, and supraspinatus muscles, primarily in dogs. The cause is unknown. Affected muscles are characterized by contracture and fibrosis. Normal tissues are replaced by dense collagenous connective tissue. Clinical signs include a nonpainful, mechanical lameness Overview of Lameness in Small Animals Clinical signs of musculoskeletal disorders include weakness, lameness, limb swelling, and joint dysfunction. Motor or sensory neurologic impairment may develop secondary to neuromuscular lesions... read more . Neurologic function is normal. Surgical release of affected tissues via tenotomy, myotenotomy, Z-plasty, or complete resection produces inconsistent results. Prognosis is guarded because of recurrence.