Right Knee Pain—Running

HISTORY: A 23-year-old runner presents with 3 months of atraumatic right knee pain that began 1 day after playing pickup basketball with friends. He localizes pain to the anterior right knee and proximal tibia, and rates it 5/10. He denies any swelling or mechanical symptoms. He reports difficulty sleeping due to pain, and uses ibuprofen to fall back asleep. He denies any prior history of knee injury. He enjoys hiking and running, and reports his knee symptoms worsen after a long hike. Typically he runs 10 miles twice weekly, but has avoided running since his knee symptoms began. PHYSICAL EXAMINATION: On examination of the right knee, there is trace swelling along the right tibial tubercle. There is no joint effusion. No varus or valgus deformity. On palpation, there is maximal tenderness just inferior to the tibial tubercle. There is no tenderness in the joint line, along the patellar facets, or on the patellar poles. There is no tenderness along the pes anserine bursa. There is flexion to 160 degrees and extension to 0 degrees. There is a negative McMurray’s test, Lachman’s test, posterior drawer test, and patellar grind test. There is pain with single leg hop on the right leg. DIFFERENTIAL DIAGNOSIS: 1. Stress injury of the anterior tibia 2. Bone tumor TEST AND RESULTS: Right knee radiographs, anterior-posterior, lateral, skyline Laurin, and Rosenberg views: - no fracture, dislocation, or osteoarthritic changes - patella is well-seated in the trochlear groove bilaterally Right tibia/fibula radiographs, anterior-posterior and lateral views: - no fracture or dislocation - hardware present in the distal fibula from previous history of fracture without any obvious loosening Noncontrast MRI of the right knee: - focal marrow edema in the anterior tibia involving the tibial tuberosity without evidence of an osseous lesion Noncontrast CT of the right knee: - small lucency with surrounding sclerosis in the tibial tubercle FINAL WORKING DIAGNOSIS: Osteoid osteoma TREATMENT AND OUTCOMES: 1. Underwent CT-guided biopsy and microwave ablation of the right tibial tuberosity lesion, with pathology confirming osteoid osteoma. 2. Post-procedure, he underwent weight-bearing as tolerated with crutches for 2 weeks. 3. At one month follow-up, he reported resolution of his right knee pain. He was started on a return to running program.