Acute left knee pain
56 year old gentleman attended Accident and Emergency with acute, generalised left knee pain following a direct injury with a door. AP and lateral radiographs of his left knee were perfomed. Exostoses were identified at the distal femur and proximal tibia. The patient noted that he was known to suffer with Multiple Hereditary Exostoses (MHE). The patient's symptoms settled spontaneously and hence, the x ray findings were thought to be incidental.
Multiple Hereditary Exostoses (or Multiple Osteochondromas) is an inherited condition which causes multiple exostoses. It has an autosomal inheritence with a 96% penetrance. Approximately 10 - 20% of individuals with MHE may have the condition as a result of a spontaneous mutation. There are two known genes that cause this disease; EXT1 located on chromosome 8q23-q24 and EXT2 located on chromosome 11p11-12. It occurs in 1 out of 50 000 people and the average age of diagnosis is 3 years. The male:female ratio is 1.5:1. It is a benign condition. Osteochondromata result from the dysplasia of the periosteal growth plate. Lesions may be sessile or pendunculated. The exostoses arise from the metaphysis, point away from the epiphysis and appear to extend down the diaphysis. On plain radiographs, sessile lesions cause metaphyseal widening whist pendunculated osseous projections extend down the diaphysis. The lesions have cortical and medullary continuity with adjacent bone. The cartilaginous cap is best delineated on MR scan. It usuallly has a thickness of 1-6mm. Exostoses increase in size and number during growth, but they may become latent at skeletal maturity. They may affect multiple bones. The most common radiograhpic distribution is at the distal femur and proximal tibia, where 70% lesions are identified. They are also common at the proximal humerus (50%), scapula (40%) and ribs (40%). They may also be found at the radius, ulna, hands, ileum and feet. Clinically, patients may present with pain secondary to a fracture at the base of the pendunculated lesion or from mechanical irritation. Neurovascular compromise may be secondary to pressure from exostoses on surrounding tissues. Limb deformity, leg length discrepancy and short stature may also be identified. Exostoses can present as a painless mass. They may even as an incidental finding, as in this case. Surgery for benign lesions is reserved for those with limb deformities, leg length discrepancies and neurovascular compromise from compression. 2-5% of patients with MHE may undergo sarcomatous degeneration. This compares with 1-2% with a solitary osteochondroma. Patients with EXT1 gene, lesions occuring near the pelvis, scapula, proximal humerus and spine are at increased risk of transformation. Signs of concern include increased size of exostosis or new onset of pain. These warrant investigation. MR is the imaging method of choice. A cartilaginous cap thickness >2cm is suggestive of sarcomatous change. Dynamic gadolinium-enhanced MR can distinguish benign cartilaginous lesions from low grade chondrosarcomas.
Multiple Hereditary Exostoses
Based on the AP and lateral X-ray views of the patient’s left knee, there is a noticeable bony protrusion on both the medial and lateral sides of the distal femur (especially in the metaphyseal region of the distal femur). These protrusions are continuous with the diaphyseal medullary cavity and are primarily pedunculated in shape (or partially broad-based), with relatively clear margins. The articular surface appears intact, with no significant narrowing of the joint space or obvious soft tissue swelling. Currently, there is no clear evidence of fracture lines or significant soft tissue damage. The overall presentation is consistent with multiple osteochondromas (hereditary multiple exostoses).
Considering the 56-year-old male patient, a clinical history suggestive of multiple exostoses, and the imaging findings, the most likely diagnosis is: Multiple Hereditary Exostoses (MHE).
If subsequent clinical presentations include increased pain, rapid growth of the exostoses, or suspected soft tissue involvement, MRI evaluation (to assess cartilage cap thickness) or biopsy may be indicated to rule out malignant transformation.
Treatment Strategies:
Rehabilitation and Exercise Prescription:
Throughout the rehabilitation process, avoid excessive loading, high-impact activities, and deep knee flexion exercises. Make sure to warm up before each session and stretch afterward to reduce the risk of soft tissue injury. Progress under the guidance of a specialized physician or physical therapist.
Disclaimer: This report is based solely on the provided imaging and clinical history for reference and does not replace professional face-to-face medical diagnosis or treatment. If there are any concerns or changes in your condition, it is recommended to consult a specialist promptly.
Multiple Hereditary Exostoses
