Bent leg is the result of a calcium:phosphorus imbalance. It is seen in young, rapidly growing kids (more often in males than in females) and in young does in the later stages of their first pregnancy or in the early stages of their first lactation. These does are either young (eg, 12 mo), extremely heavy milkers, or carrying twins or triplets. Bent leg is sometimes compounded by rickets (see Rickets).
Clinical Findings and Diagnosis
Bent leg starts with lateral or medial bowing of one or both radii. Later changes may consist of lateral deviation of the digits on the fore- or hindfeet; lameness and reluctance to walk; an arched back; and soft swelling and pain in the carpal, metacarpophalangeal, tarsal, and metatarsophalangeal joints. Diagnosis of the epiphysitis that occurs in bent leg can be confirmed with radiography.
Conditions that have been implicated in the cause include an excess of dietary calcium with a calcium:phosphorus ratio of >1.4:1 (generally >1.8:1), excess protein intake (has caused epiphysitis in other species), excess dietary iron (has reduced serum phosphorus levels in lambs by decreasing vitamin D metabolite formation), and housing of kids or lack of vitamin D caused by prolonged overcast weather and low vitamin D levels in the feed. Carotene has an antivitamin D effect. Vitamin D has poor stability in prepared feed, especially when mixed with minerals. Alfalfa is high in calcium (1.4% calcium to 0.2% phosphorus) and protein. Owners frequently keep kids on fresh milk for prolonged periods because often no commercial outlet for the milk is available.
Treatment and Control
Once the probable cause(s) is identified, the diet should be corrected and the appropriate supplement given—usually injectable vitamin D and phosphorus or oral balanced calcium/phosphorus supplements (or both).
Predisposing factors also must be corrected. The diet of growing kids should be changed to slow their growth rates. The mating of very young does should be discouraged. Buck kids should be separated from doe kids by 3 mo of age to avoid unplanned matings. Young does in milk with limb deformities should be managed so that full lactation is discouraged, eg, by not milking out fully and drying off as early as possible.
Treatment stops limb deformities from worsening and should improve them to a great extent. However, a return to completely normal limbs is rare.
Last full review/revision March 2012 by David M. Sherman, DVM, MS, DACVIM