A 32-year-old male, presented with pain and swelling along the anterior aspect of the distal left leg for the past 4 months. On examination, a fluctuant swelling was palpated with a deep-seated hard projection. The patient underwent an X-ray of the left leg as well as a local site ultrasound for the swelling.
Anteroposterior and lateral radiographs (Figures 1a and 1b) of the left leg showed the presence of a well-marginated, sessile bony lesion arising from the anterolateral aspect of the distal diametaphyseal region of the left tibia with continuity of trabecular pattern with the underlying bone. Soft tissue swelling is visualised overlying the bony lesion as well as along the anterior aspect of the ankle joint.
Ultrasound images of the site of swelling show the bony lesion (Figures 2a and 2b), with its surface appearing echogenic with posterior shadowing and a thin hypoechoic covering of maximum thickness ~1.5 mm, suggesting the cartilage cap.
A thickened common tendinous sheath of the left extensor digitorum longus (EDL) and peroneus tertius with tenosynovial effusion, showing a predominantly clear appearance with few internal echoes, is seen (Figures 3a and 3b). The tendons appear mildly thickened, without significant internal vascularity; however, minimal synovial thickening surrounding them shows increased peritendinous vascularity (Figure 4).
Background
Osteochondromas are benign bone tumours arising from cartilage-capped bony projections on the surface of bones. Also considered to be developmental anomalies, they commonly occur in long bones like the femur or tibia, particularly in adolescents and young adults. Though usually asymptomatic, they can cause pain or functional issues.
Clinical Perspective
Osteochondromas can be multiple or solitary, with complications most commonly seen with multiple exostoses, as seen with multiple hereditary exostosis syndrome. Complications of osteochondromas include deformities, fractures, vascular compromise and pseudoaneurysm formation, neurologic sequelae, overlying bursa formation, mechanical irritation on surrounding soft tissues (for example, localised tenosynovitis) and malignant transformation [1].
Imaging Perspective
While X-rays are the ideal modality for diagnosing the primary features of an osteochondroma, an ultrasound or an MRI will help delineate the features of its associated complications. X-rays reveal the characteristic metaphyseal bony projection, with medullary continuity with parent bone, often accompanied by signs of surrounding soft tissue swelling or deformity [2]. MRI provides detailed views of the osteochondroma’s cartilage cap and highlights surrounding soft tissue inflammation, including thickening of the tendon sheath indicative of tenosynovitis. The tenosynovitis can be classified into active exudative (associated with infection or gout, predominant fluid accumulation), acute proliferative (seen with inflammatory conditions, synovial proliferation predominant), chronic and stenosing tenosynovitis, based on the imaging findings. Chronic synovitis is seen as marked (when active) or mild sheath thickening (when inactive), fluid accumulation, hyperaemia within and around tendons, and rice bodies formation.
Outcome
Treatment of such cases typically involves surgical resection of the tumour to relieve pressure on surrounding tendons. Concurrently, anti-inflammatory medications or corticosteroid injections may manage the symptoms related to tenosynovitis. Physical therapy can aid in recovery and restore tendon function.
Take Home Message / Teaching Points
Osteochondromas, even though benign, can become symptomatic in cases of fractures, vascular damage, compression of a peripheral nerve or spinal cord, mechanical irritation of soft tissues, or malignant transformation. It is important to identify these complications for appropriate patient management and prognosis, with some of them being able to be diagnosed on ultrasound, and without the need of an MRI.
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Secondary tenosynovitis
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1. From the left lower leg X-ray:
2. Ultrasound findings:
3. Clinical signs consistent with imaging findings:
Based on imaging and clinical data, the following possibilities are preliminarily considered:
In summary, the most likely lesion is osteochondroma with concomitant local tenosynovitis.
Taking into account the patient's age (32 years), disease course (4 months of chronic pain and swelling), radiological findings (bony outgrowth continuous with the marrow cavity, surrounding soft tissue inflammatory changes), and clinical examination results, the most likely diagnosis is: Osteochondroma of the distal left lower leg with concurrent local tenosynovitis.
If further confirmation of the pathological nature is needed, in rare cases, surgical resection followed by pathological examination can be performed to rule out the extremely rare possibility of malignant transformation.
Once symptoms are under control and the wound/lesion is stable, a gradual and individualized rehabilitation program should be adopted:
Example training plan:
• Weeks 1–2: 3 sessions per week, 20 minutes of walking on flat ground each time. During walking, perform moderate ankle dorsiflexion and plantarflexion exercises.
• Weeks 3–4: Based on previous tolerance, increase total duration to 30 minutes, followed by simple stretching or light ankle strength training.
• Week 5 onward: If no significant discomfort, introduce low-impact cycling or water walking as cross-training, ensuring lower limb joint stability without excessive load.
During the rehabilitation process, follow-up imaging and re-examinations are advised. Any abnormal pain or worsening symptoms should prompt immediate medical evaluation to rule out secondary pathology or progression.
This report is for reference and analysis only. It does not replace an in-person clinical visit or professional medical diagnosis. Specific treatment should be based on the actual clinical situation and professional medical advice.
Secondary tenosynovitis
