Lameness Associated with the Stifle and Pelvic Regions

The reciprocal apparatus of the hindlimb means that similar lameness characteristics are shared by many causes of hindlimb lameness in both the proximal and distal parts of the limb. It is rarely possible by evaluation of gait alone to identify accurately the source of pain causing lameness, although a combination of clinical signs may lead the clinician to suspect a site of pain. It is only through the diligent use of local analgesic techniques that the source of pain can be reliably determined, and interpretation of these is not always straightforward. To my knowledge, there have been no epidemiological studies investigating the relative incidence of different sites of pain causing hindlimb lameness, and any such study would be heavily dependent on the accuracy of diagnosis. It is my impression, after 22 yr of lameness investigation, that lameness ascribed to the pelvic region is often overdiagnosed. In my opinion, comprehensive clinical examinations combined with local analgesic techniques are often under utilized, in part because of the inherent dangers of hindlimb lameness investigation. Thus, pain causing lameness in the more distal parts of the limb is often overlooked. However, in my experience these dangers are overemphasized and in a large proportion of horses thorough clinical examinations and local analgesic techniques are possible with minimal risk, provided that horses are quietly and appropriately restrained. Over a 3-yr period (January 1999 to December 2001, inclusive) I investigated 318 horses of 2 yr of age or older with hindlimb lameness in which a definitive diagnosis of the source of pain was established; 49 horses (15%) had lameness associated with the stifle region and only 29 horses (9%) had lameness associated with the pelvic region. Horses presenting with restricted hindlimb impulsion and back stiffness, which were ultimately diagnosed with sacroiliac joint pain, were excluded from this assessment. A further 22 horses (6% of 340) with unilateral hindlimb lameness were evaluated in this period and a definitive diagnosis of the source of pain causing lameness could not be established, despite thorough clinical examination, comprehensive local analgesic techniques and nuclear scintigraphic examination. These figures, based on a referral population of horses and restricted to horses 2 yr of age or older, may overestimate the incidence of upper hindlimb lameness in the general horse population. In my opinion it is critical to be able to reliably perform perineural analgesia of the tibial and fibular nerves in order to exclude definitively the hock region and distal parts of the limb as po-