An Unusual Case Of Knee Pain In A Female Collegiate Runner

HISTORY: 18 yo female collegiate runner with history of functional hypothalamic amenorrhea presents with insidious onset left knee pain for 1.5 years. Pain is localized to the anterior knee at the lateral patella and exacerbated by running, jumping, descending stairs, and direct contact/pressure. She endorses swelling at the area of tenderness but denies any associated instability or mechanical symptoms. Rest and patellar taping provide temporary relief. PHYSICAL EXAMINATION: Localized mild swelling at lateral patellar facet, tender to palpation with palpable bump. No joint effusion. No tenderness at medial/lateral joint line, quadriceps/patellar tendons, or tibial tubercle. Full active range with painless extension but flexion-induced pain at end-range. Strength 5/5 in flexion and extension. No pain or laxity on valgus/varus stress test. Negative Lachman’s and McMurray’s, but positive patellar apprehension and grind tests. Valgus knee deviation with poor proprioception on single leg squat. DIFFERENTIAL DIAGNOSIS: Patellar Stress Fracture, Patellofemoral Pain Syndrome, Lateral Patellar Compression Syndrome, Chondromalacia Patella, Patellar Tendinitis TESTS AND RESULTS: -Left knee radiographs: no bony abnormality or joint effusion, normal patellar alignment (sunrise view), patella alta (lateral view) -Left knee MRI w/o contrast: inflammation and thickening with cystic vs calcific changes of lateral patellofemoral ligament (LPFL) at patellar attachment, edema within anterior and inferior aspects of patella FINAL WORKING DIAGNOSIS: LPFL interstitial tearing with associated cystic vs calcific changes, and patellar bone stress injury TREATMENT AND OUTCOME: 1. Left knee arthroscopy with excisional biopsy of LPFL insertion and lateral lengthening. 2. Post-operative plan: Weight-bearing as tolerated with hinged patellar stabilizing brace and crutches during initial period. Range of motion limited to 0° to 30° with an emphasis on full extension, progressed to 60° with quadriceps strengthening at 2 weeks and 90° at 4 weeks. Progressive strengthening exercises introduced at 6 weeks, followed by a plyometric program and initiation of forward running once there is full painless range of motion and normal strength. Gradual return to play per sport-specific rehabilitation protocol by 4 to 6 months.