A Rare Cause of Knee Pain in a Healthy Male Ultra-marathon Runner

Abstract

HISTORY: A 58-year-old healthy male ultra-marathon runner presented with a 3-month history of atraumatic, gradually worsening right-sided anterior knee pain, aggravated by activity and associated with prominent morning stiffness and pain. Night pain was absent. Oral and parenteral NSAIDs provided no relief, nor did massaging. No history of smoking, alcohol or prior corticosteroid use was reported. PHYSICAL EXAMINATION: The R-knee was slightly swollen with no obvious deformities. No clinical intra-articular effusion was noted. Palpation revealed tenderness over the quadriceps tendon insertion and superomedial knee. In addition, the patient showed significant weakness of the right gluteus medius and quadriceps muscles. Tests for mechanical disruption and intra-articular injury were negative. Further examination of the hip and ankle joints as well as the general systemic examination were unremarkable. DIFFERENTIAL DIAGNOSIS: Quadriceps tendinopathy Patellar tendinopathy Patello-femoral pain syndrome Chondromalacia patellae Patellofemoral osteoarthritis Iliotibial band syndrome Other sources of knee pain (such as arthritis and gout) TEST AND RESULTS: Ultrasound: No soft tissue abnormalities. Suggestive area of a bony infarct in the distal femur. Plain radiographs (R-knee): Hypo-lucent area-distal femur (proximal to the condyles) MRI Knees: Bilateral areas of increased signal in the distal femoral shaft, suggestive of bilateral bony infarcts, were identified. Blood tests: within normal limits. FINAL WORKING DIAGNOSIS: Spontaneous osteonecrosis of the knee (SPONK)/ Ahlback`s Disease. TREATMENT AND OUTCOMES: 1. Initial management: Conservative - physical therapy and eccentric strengthening exercises. 2. Final outcome: Returned to physical activity, but it is still debated whether this athlete should return to full participation in ultra-marathon running.