Other dogs may refuse to go up stairs or jump. Lameness may be evident. The leg may be carried with the stifle joint flexed, but may be touched to the ground every third or fourth step at fast gaits. In more severe disease, the dog may exhibit a crouching, bowlegged stance with the feet turned inward. Most of the dog's weight will be borne on its front legs.
Permanent luxation renders the quadriceps muscle ineffective in extending the stifle.
Diagnosis is accomplished by palpating the knee joint to ascertain extent of movement of the patella. This may require sedation or light anesthesia. The severity of the condition will be assigned one of four grades. The dog may occasionally carry the affected limb. The patella easily luxates manually at full extension of the stifle joint, but returns to the trochlear groove when released.