HINDLIMB INJURIES

In the hindlimb, hip dysplasia and osteoarthritis of the hip, stifle, and tarsus are not uncommon and usually a consequence of preexisting developmental orthopedic disease.⁴² Sporting dogs can also develop gracilis-semitendinosus myopathy and contracture, iliopsoas muscle trauma leading to femoral neuropathy, cruciate ligament rupture, patellar tendonitis, long digital extensor tendonitis due to proximal luxation, and gastrocnemius head or popliteal muscle avulsion injury.^24,36,43,44 Chronic injuries of the hindlimb include Achilles tendon rupture, iliopsoas myopathy, partial cruciate ligament rupture, and lumbosacral disease.^5,45,46

Below are specifics on identifying and treating iliopsoas muscle injury, popliteal muscle avulsion, gastrocnemius muscle avulsion, superficial digital flexor tendon luxation, and Achilles tendon injury—conditions many practitioners may not be as familiar with.

The psoas major muscle arises from the transverse processes of the second and third lumbar vertebrae and the ventral vertebral bodies of the fourth through seventh lumbar; it then joins with the iliacus muscle (which arises from the ilium) to become the iliopsoas muscle that inserts on the lesser trochanter of the femur.⁶ The femoral nerve passes through the muscle fibers of the psoas and iliopsoas muscles, and with hemorrhage in this area or tearing of the muscle, compression and stretching of the nerve from the hematoma may cause a femoral neuropathy.^44,47,48

Injury to the iliopsoas muscle is not as uncommon as once thought.⁴⁹ Dogs that are infrequently active and overextend themselves can experience this injury as well as athletes. Affected dogs may not be lame but may show signs of decreased performance, difficulty rising, and a shortened stiff gait in the hindlimbs.⁵⁰ In severe cases, they may have signs of femoral nerve paralysis. A sprain of the muscle will be mildly painful on palpation, but when there has been hemorrhage into the muscle fibers, severe pain can be present because of compression and inflammation of the closely related femoral nerve.⁴⁷

The injury can be diagnosed on ultrasonographic examination.⁴⁹ Treatment of mild cases often involves therapeutic ultrasonography, passive range of motion exercises, and a gradual return to activity.⁴⁹ If this therapy fails, surgical resection of the iliopsoas tendon of insertion can resolve the clinical signs.⁴⁷

Popliteal muscle avulsion

The popliteal muscle flexes the stifle and internally rotates the tibia in relation to the femur. It originates on the lateral femoral condyle with its sesamoid near its origin, crosses the stifle joint caudally, and then inserts on the proximal medial tibia.⁶

When avulsion occurs, it is at the lateral femoral condyle, and pain will be present on extension of the stifle as well as when the caudal aspect of the stifle is palpated.⁵¹ On radiographs, the popliteal sesamoid at the caudal aspect of the stifle joint will be displaced distally. Surgery to reattach the muscle to the lateral femoral condyle is recommended, but as with gastrocnemius avulsion (see below), return to peak performance is unlikely.⁴