Findings
In case 1, there is a striking loss of the musculature about the knee/fatty replacement. On the radiographs, there is a slightly low-lying patella with mild flexion of the knee. There are subtle growth recovery lines. In case 2, there is a marked asymmetry of the abnormal right and normal left lower extremities. The bones of the right lower extremity are much more gracile than the right. The right patella is very low lying and greater flexion is seen of the right knee. Markedly abnormal varus alignment of the right foot and ankle is present as compared to maintained alignment of the left foot and ankle.
Diagnosis: Poliomyelitis
Poliomyelitis or polio is a viral infection that has been essentially eradicated in the Western Hemisphere but does still exist in other parts of the globe. The virus typically infects children but can also infect adults. The virus infects and destroys motor neurons most commonly of the spinal cord but can also affect the brain stem and motor cortex. Only approximately 1% of those infected develop the paralytic form of polio. Although the disease has been essentially eradicated in the West from vaccine development, cases are still seen.
The findings relate to loss of the motor neurons with a complete wasting of the musculature and fatty replacement. This can lead to the abnormal alignment say of the patella or very frequently malalignment of the foot. In the growing skeleton, markedly gracile bones can develop as well as marked limb length discrepancies. Given that growth can still occur, episodic growth recovery lines are seen. Although not always the case, there is frequently an asymmetric involvement of the motor neurons and as seen in case 2, there can be marked asymmetry with involvement of one limb and a spared contralateral limb.