Referred Pain to the Knee in Hip Diseases : A Case Series Study

Abstract

Patient 1, a 75-year-old woman with a past history of osteoarthritis of the right knee and Parkinson disease, had a subarachnoid hemorrhage. She complained of right knee pain during her rehabilitation. It turned out that she had sustained a right trochanteric fracture after falling out of bed in another hospital. Patient 2, an 86-year-old woman with a past history of rheumatoid arthritis, was treated with the Gamma nail technique for a left trochanteric fracture. She described experiencing pain in the region from the left knee to the lateral side of the left thigh during her rehabilitation, about two months after the hip operation. X-ray and computed tomography images showed varus displacement of the femoral head due to screw cut-out. In each of these cases, it took some time for us to detect the underlying hip diseases. The dermatome shows regions of the skin innervated by each single spinal segment. Similarly, the sclerotome shows regions of bone and periosteum innervated by each single spinal segment. According to Inman and Saunders's sclerotome, the proximal portion of the femur is mainly innervated by L3, L4 and L5. On the other hand, in dermatome perspective, L3, L4 and L5 innervate the knee and region around the knee. It means that hip diseases can cause referred pain to the knee. Untypical pain in distant regions from the hip joint makes it difficult to examine the hip joint and causes delay in an accurate diagnosis, as in the cases just described. Therefore, we should keep in mind that hip diseases can cause referred pain to the knee.