The clinical signs for dogs with ACL tears are quite variable. Subtle lameness, exacerbated by exercise often occurs. These patients also exhibit lameness when first getting up in the morning. The lameness may subside with rest but recurs with activities like hiking or ball playing. However, many dogs have persistent, moderate to severe lameness. The degree of lameness is influenced by the progressive osteoarthritis seen with ACL pathology, degree of tearing and concurrent meniscal tears.
Almost all dogs with ACL problems sit to the side, even when sitting for a treat. Sometimes the lameness comes on quickly but often it's a gradual progressive problem. It is not uncommon for the problem to wax and wane for weeks or even months.