Osteoid osteoma of the talus adjacent to the subtalar joint: a rare location and diagnostic challenge

Abstract

Introduction and importance:

Osteoid osteoma is a common benign bone tumor, but lesions located in the talus, especially those adjacent to the subtalar joint, are relatively rare and prone to misdiagnosis. Its clinical and imaging manifestations are often atypical, which can lead to delayed diagnosis and inappropriate conservative treatment. Accurate imaging evaluation and appropriate surgical management are critical for symptom relief and functional recovery.

Case presentation:

We present a 20-year-old male with chronic left ankle pain that worsened at night and with weight-bearing. Initial MRI suggested bone marrow edema and ligament injury, leading to a misdiagnosis of ankle synovitis and sprain. Subsequent CT clearly identified a 5-mm nidus at the medial inferior margin of the left talus. The patient underwent open resection with intraoperative CT-guided K-wire localization. Postoperative histopathological examination confirmed osteoid osteoma. At the 1-year follow-up, the patient was pain-free and had fully resumed daily activities.

Clinical discussion:

Talar osteoid osteoma is prone to misdiagnosis because its symptoms resemble those of ankle sprain, synovitis, or impingement. CT is the gold standard for detecting the nidus, while MRI frequently shows nonspecific bone marrow edema. Surgical excision remains a reliable treatment method. CT-guided K-wire localization improves accuracy, minimizes bone damage, and ensures complete resection, avoiding incomplete ablation and the recurrence risk associated with percutaneous radiofrequency ablation.

Conclusion:

Osteoid osteoma of the talus is a rare but significant cause of chronic ankle pain and is easily misdiagnosed. CT is essential for early and accurate diagnosis. For juxta-articular lesions, CT-guided K-wire localization followed by open resection is safe and effective, completely relieving symptoms and achieving good long-term outcomes.

Introduction

Osteoid osteoma (OO) is a benign osteoblastic tumor that was first described and defined as an independent lesion entity by Jaffe in 1935^[1^]. OO accounts for 2–5% of all primary bone tumors and 10–11% of benign bone tumors^[2,3^]. The disease commonly occurs before the age of 30, with a male-to-female ratio of approximately 2:1^[2,4^].

OO is classified into three types based on the location of the lesion within the bone: cortical, cancellous, and subperiosteal^[5^]. It often occurs in the diaphysis and metaphysis of long bones, mainly including the femur and tibia. OO in the foot is uncommon, accounting for approximately 2–10% of all cases, and is a rare cause of joint pain^[6,7^]. The preferred site of involvement in the foot is the talus, with an incidence of 2–10% and most lesions (97%) are located at the talar neck^[8^].

A typical feature of OO is pain that worsens at night and is relieved by non-steroidal anti-inflammatory drugs (NSAIDs) or salicylates^[3,6,9^], which may be present in 50–100% of cases^[6,9–11^]. Diagnosis of juxta-articular lesions is more challenging because the symptoms overlap with those of monoarticular disease. For example, in the talus, this condition can resemble ankle impingement, ankle sprains, and inflammatory arthropathy.

HIGHLIGHTS

• A talar osteoid osteoma adjacent to the subtalar joint is rare and easily misdiagnosed.

• CT is the gold standard for identifying the nidus and guiding precise resection.

• CT-guided K-wire localization followed by surgical excision achieves complete pain relief and excellent outcomes.

We report the case of a 20-year-old patient with an OO in the left talus adjacent to the subtalar joint. Histopathological examination after curettage confirmed the diagnosis. At follow-up, the patient reported no pain or other discomfort. This case report complies strictly with the updated 2025 Revised SCARE checklist^[12^]: all mandatory reporting items, including clinical timeline, patient subjective experience, medication/allergy history, and standardized complication documentation, are fully supplemented and presented within the Case Presentation.

Chronological clinical timeline

• 6 months preoperatively: Insidious left ankle aching and swelling developed; the initial MRI misdiagnosed the lesion as ankle synovitis, and the patient was treated with rest and cold compresses.

• 4 months preoperatively: A minor left ankle sprain triggered recurrent severe pain; a second MRI confirmed a ligament injury, which was treated with an intra-articular corticosteroid injection and oral loxoprofen.

• Referral stage: Persistent, refractory night and weight-bearing pain prompted referral to our center; CT identified a 5 mm subperiosteal OO nidus adjacent to the subtalar joint.

• Operation day: CT-guided K-wire localization and complete open resection under spinal anesthesia.

• Two weeks postoperative: complete resolution of subjective pain and obvious improvement in ankle mobility.

• At 3 months postoperatively, MRI showed resolution of bone marrow edema and partial recovery of ankle function.

• One year postoperatively: full functional recovery; CT confirmed radical lesion removal without recurrence.

Medication and allergy history and patient’s subjective perspective

A 20-year-old male patient denied any history of drug allergy, food allergy, or chronic systemic disease. From symptom onset to definitive surgery, he received sequential conservative treatments, including rest, ice compression, intra-articular corticosteroid block, and oral loxoprofen for pain control. From the patient’s perspective, the ankle pain was persistent and markedly exacerbated at night and during walking; NSAIDs could only achieve transient, mild pain relief, and all conservative measures failed to resolve the discomfort permanently. After surgical resection, the patient reported dramatic pain relief on postoperative day 1, and all abnormal painful sensations disappeared entirely within 2 weeks.

Case presentation

A 20-year-old male student with no significant past medical or surgical history presented to the clinic. He reported chronic pain and swelling in the left ankle joint that had begun 6 months before surgery, without an obvious cause. The pain was intermittent and was aggravated by walking and at night. An ankle MRI performed at a local hospital showed bone marrow edema in the medial aspect of the left talus, accompanied by surrounding soft-tissue contusion and edema (Supplemental Digital Content Figure S1, available at: https://links.lww.com/IJSCR/A158). He was diagnosed with ankle synovitis and received non-surgical treatments, including rest, ice, and measures to reduce swelling.

But the pain recurred after the patient sprained his left ankle 2 months later. A second MRI scan was recommended due to his persistent pain (Supplemental Digital Content Figure S2, available at: https://links.lww.com/IJSCR/A158). The images showed a significant recurrence of bone marrow edema in the left talus, accompanied by injuries to the anterior talofibular ligament and the medial deltoid ligament. The patient underwent an intra-articular corticosteroid injection for block therapy and was given oral loxoprofen as an adjunct for pain management.

However, the pain in the left ankle continued to worsen during weight-bearing activities and at night. The patient was referred to our medical center for further evaluation, and CT identified a well-circumscribed, small, round, hyperdense central nidus located in the medial-inferior portion of the talus. The lesion was surrounded by rim-shaped reactive osseous sclerosis, without intra-articular bone fragments or articular-surface collapse (Fig. 1A–D). MRI showed a low-signal-intensity area on the medial side of the talus and displayed extensive high-signal bone-marrow edema surrounding the talar nidus. Diffuse perilesional inflammatory edema was observed within the talus and in the adjacent subtalar joint (Fig. 1E–G). Preoperative baseline laboratory tests were obtained at admission. All results were within normal reference limits: white blood cell count 6.33 × 10⁹/L, red blood cell count 5.56 × 10¹²/L, platelet count 304 × 10⁹/L, C-reactive protein 3.47 mg/L, erythrocyte sedimentation rate 6.28 mm/h, and serum uric acid 355.18 μmol/L. These normal inflammatory and metabolic biomarkers exclude infectious, inflammatory, and gouty etiologies as the cause of the patient’s chronic ankle pain.

Figure 1.

(A–C) CT images clearly demonstrated a 5-mm, well-circumscribed, hyperdense nidus at the medial-inferior margin of the left talus, surrounded by a thin rim of reactive osseous sclerosis. (D) Three-dimensional CT reconstruction confirmed the juxta-articular location of the nidus adjacent to the subtalar joint and superior to the sustentaculum tali, with key anatomical landmarks labeled. (E-G) MRI showed no significant change in bone marrow edema of the left talus compared with previous scans, with a low-signal-intensity shadow on the medial side of the talus, accompanied by injury to the left anterior talofibular ligament and medial deltoid ligament.

Preoperatively, the patient underwent CT-guided percutaneous localization in the operating room under spinal anesthesia (Fig. 2A). A K-wire was inserted percutaneously toward the lesion under continuous axial CT guidance, with repeated adjustments of the needle path until the tip of the K-wire was confirmed to have precisely reached the center of the 5 mm talar lesion. The K-wire was then temporarily fixed to serve as an intraoperative navigation marker (Fig. 2B). A medial approach to the subtalar joint was adopted for open resection. After skin incision and blunt dissection of the subcutaneous tissue and flexor retinaculum, the medial aspect of the talus and the subtalar joint capsule were exposed. Under direct visualization, we followed the pre-inserted K-wire to identify the lesion location. Intraoperatively, the lesion presented as a well-circumscribed, firm, hyperemic bony nodule located immediately superior to the sustentaculum tali and adjacent to the medial subtalar articular surface (Fig. 2B). The overlying subtalar articular cartilage was grossly intact with no evidence of erosion or focal defect. Using a small osteotome and curette, we performed en bloc resection of the nidus along with a thin rim of surrounding reactive sclerotic bone, guided by the pre-positioned K-wire. The resected specimen measured approximately 5 mm in diameter, with a gritty ossified central nidus and surrounding sclerotic bone (Fig. 2C–D). Complete resection was confirmed by intraoperative palpation and direct visual inspection of the bony cavity. The wound was closed in layers after thorough hemostasis. Postoperative histopathological examination confirmed the diagnosis of OO, demonstrating typical anastomosing osteoid trabeculae lined by osteoblasts within a vascular stroma, accompanied by surrounding reactive bone sclerosis (Fig. 3).

Figure 2.

(A) Preoperative CT-guided localization of the body surface position of an osteoid osteoma. (B) Intraoperatively, the tumor was observed to be located above the subtalar joint. (C–D) The tumor was completely resected, with a diameter of approximately 5 mm.

Figure 3.

Postoperative histopathology confirmed that the nodule was an osteoid osteoma: interconnected osteoid-woven bone trabeculae lined by benign osteoblasts within a vascularized fibrous stroma and without malignant features.

The patient’s pain was significantly alleviated on the first day after surgery, with the VAS score decreasing from 8 to 2, and it was completely resolved by 2 weeks postoperatively. The preoperative range of motion of the left ankle was as follows: dorsiflexion 5°, plantarflexion 22°, with significant limitation of inversion and eversion. At 2 weeks after surgery, dorsiflexion increased to 16° and plantarflexion to 40°. At the 1-year follow-up, dorsiflexion was 21° and plantarflexion 46°, and inversion/eversion motion returned to the level of the unaffected contralateral ankle with no movement restriction. Preoperatively, the patient scored 42 on the American Orthopaedic Foot and Ankle Society (AOFAS) ankle-hindfoot scale and 31 on the Foot and Ankle Ability Measure (FAAM) daily activity scale. At the 3-month postoperative follow-up, the AOFAS score increased to 79, and the FAAM score rose to 76. 1 year after surgery, the AOFAS ankle-hindfoot score reached 96, and the FAAM score was 94, with complete recovery of ankle function, including walking, jogging, and jumping without functional restriction.

MRI re-examination at 3 months postoperatively demonstrated that the signal of bone marrow edema in the original lesion area had significantly decreased compared to preoperative imaging, the extent of high signal within the talus had markedly reduced, and no abnormal enhancing foci or new lesions were observed (Supplemental Digital Content Figure S3, available at: https://links.lww.com/IJSCR/A158). At the 1-year postoperative follow-up, the patient reported no pain and had resumed daily activities, with no complaints of discomfort. At the 1-year postoperative follow-up, CT of the left ankle and subtalar joint (Supplemental Digital Content Figure S4, available at: https://links.lww.com/IJSCR/A158) demonstrated complete resection of the previously identified OO nidus at the medial inferior margin of the talus. No residual hyperdense lesion, reactive periosteal sclerosis, or bone cystic change were detected at the surgical site. The articular surface of the subtalar joint remained intact without cartilage erosion, subchondral collapse, or secondary osteoarthritic changes. The bone remodeling in the lesion curettage area was satisfactory, with uniform trabecular reconstruction, no local radiolucent defects, and no signs of tumor recurrence.

Perioperative and postoperative follow-up complication records: No intraoperative complications occurred, including neurovascular injury, articular cartilage damage, or incomplete lesion resection. No short-term postoperative adverse events were observed, such as incision infection, hematoma, delayed wound healing, or persistent numbness. At the 3-month and 1-year long-term follow-ups, no secondary complications, including post-traumatic arthritis, bony malunion, or tumor recurrence, were detected via clinical examination and serial imaging. No reoperation or secondary intervention was required throughout the entire follow-up period.

Contribution to the literature

Although talar OO is a well-recognized entity, this case adds incremental clinical evidence in three respects: it describes a rare subperiosteal, juxta-subtalar location that is highly prone to misdiagnosis; it details a CT-guided K-wire localization technique suitable for deep, small juxta-articular lesions; and it provides complete 1-year functional and imaging prognostic data. This report provides a practical diagnostic and therapeutic reference for clinicians managing chronic ankle pain of obscure origin.

Discussion

OO is a benign bone tumor with limited growth potential, primarily involving the talus and calcaneus in the foot and ankle^[4,13^]. The lesion in this case is located in the subperiosteal region adjacent to the medial subtalar joint of the talus, which is a rare para-articular site with significant diagnostic difficulty. One of the most prominent features of juxta-articular and subperiosteal OO is a high rate of delayed diagnosis and misdiagnosis. Typical symptoms include chronic pain and swelling of the ankle joint, worsening at night, and relief with NSAIDs^[9,10^]. However, these manifestations are often misdiagnosed as ankle sprain, synovitis, impingement syndrome, and osteoarthritis. The literature has reported an average delay of 22 months from symptom onset to diagnosis^[4^]. Plain radiography is generally considered the preferred imaging examination for ankle pain, but it lacks characteristic sclerosis and periosteal reaction for subperiosteal lesions, with a detection rate of only 66%^[4^]. CT is the gold standard for the diagnosis of OO, as it can clearly show the location, size, and surrounding reactive bone of the nidus^[11,14,15^]. Holkar et al compared the diagnostic accuracy of MRI and CT and found that MRI had a diagnostic accuracy of only 3% for OO, while that of CT was 67%^[14^]. Jordan’s systematic review included 223 cases of OO in the foot and ankle and found that the rate of missed diagnoses on MRI was 34%^[4^]. We systematically considered the following differential diagnoses for chronic ankle pain in this young patient, with explicit evidence-based exclusion criteria: (1) Chronic ankle sprain with lateral ligament instability: Although the patient had a history of ankle sprain and MRI showed ligament injuries, persistent nocturnal pain and failure of repeated conservative treatments did not align with uncomplicated ligament injury, and the definitive nidus identified on CT further ruled out simple sprain as the primary etiology. (2) Idiopathic ankle synovitis: This was initially suspected at the local hospital; however, intra-articular corticosteroid injection yielded no sustained relief, and CT demonstrated an intraosseous nidus rather than isolated synovial proliferation, excluding primary synovitis. (3) Talar stress fracture: The patient had no history of high-intensity repetitive trauma or overuse, and CT showed a well-circumscribed round nidus with surrounding sclerosis rather than a linear fracture line or periosteal reaction, which was inconsistent with stress fracture. (4) Osteoblastoma: As a key differential of osteoblastic tumors, osteoblastoma typically exceeds 2 cm in diameter with expansile bone destruction, and the 5-mm lesion size in this case, along with the typical nidus-sclerosis pattern and final histopathology, ruled out osteoblastoma. (5) Gouty arthritis: Serum uric acid was within the normal range (355.18 μmol/L), and there was no history of acute episodic redness, swelling, and severe pain, and no tophi or erosive bone changes were observed on CT, excluding a gouty etiology. (6) Osteomyelitis and infectious arthritis: The patient had no systemic symptoms such as fever or chills, all inflammatory biomarkers (WBC 6.33 × 10⁹/L, ESR 6.28 mm/h, CRP 3.47 mg/L) were within normal limits, and CT showed no bone destruction, sequestrum, or extensive periosteal reaction, ruling out infection. (7) Osteochondral lesion of the talus (OLT): The lesion was located in the subperiosteal region of the medial inferior aspect of the talus adjacent to the subtalar joint, rather than the typical weight-bearing articular surface of the talar dome, and CT showed no articular cartilage collapse or osteochondral fragment, and the presence of a classic nidus did not support OLT. Whole-body bone scintigraphy was not performed in this case. Given the pathognomonic CT features, solitary lesion presentation, and definitive histopathological confirmation, a bone scan was considered not mandatory for the diagnostic workup in accordance with current clinical practice for typical OO. However, the final diagnosis still requires histopathological examination.

In cases where non-surgical treatment fails, invasive treatment options need to be considered. Surgical excision is the preferred treatment for symptomatic OO^[16,17^]. Arthroscopic resection of the nidus offers advantages such as clear visualization, thorough excision, minimal damage to normal bone, simultaneous treatment of synovitis, and rapid recovery^[18,19^]. Percutaneous CT-guided radiofrequency ablation represents a minimally invasive alternative for OO treatment with reported satisfactory clinical outcomes. This technique relies on indirect imaging guidance without direct intraoperative visualization of the lesion boundary, and histological specimens are unavailable for intraoperative pathological confirmation^[18,20^]. For juxta-articular lesions adjacent to cartilage, the thermal ablation process may pose potential risks to adjacent articular cartilage tissue. Open resection with CT-guided K-wire localization allows direct intraoperative visualization of the nidus, permits complete gross resection, and yields specimens for definitive histopathological diagnosis. This open approach is particularly suitable for small juxta-subtalar lesions where arthroscopic access is technically challenging.

In our case, the OO was located adjacent to the medial side of the subtalar joint of the talus and above the sustentaculum tali, with a size of approximately 5 mm ×5 mm ×5 mm. When arthroscopic surgery was deemed difficult and there was concern that the lesion might not be found intraoperatively, we chose to pre-drill a K-wire into the nidus under CT guidance during surgery for localization, then follow the K-wire to locate and completely resect it.

Conclusion

In summary, OO of the talus is a rare but significant cause of chronic ankle pain. It is highly prone to misdiagnosis or to being missed due to atypical early clinical and imaging manifestations. CT is the key examination for early and accurate diagnosis. For patients with chronic ankle pain after trauma that worsens at night and is relieved with NSAIDs, and in the absence of signs or imaging abnormalities indicating ankle instability or ligament injury, OO should be included in the differential diagnosis.

Ethical approval

No ethical approval is required in this case report as per our institutional guidelines.

Consent

Written informed consent was obtained from the patient for the publication of this case report and accompanying images. A copy of the written consent is available for review by the Editor-in-Chief of this journal upon request.

Sources of funding

No funding was received for this study.

Author contributions

H.H. and L.Y.: Research conception and design, manuscript drafting. X.J.Q. and Q.L.: Collection of clinical and imaging data. G.C.C.: Revision and approval of the final version of the manuscript. All authors have read and approved the final manuscript.

Conflicts of interest disclosure

The authors declare no conflict of interest.

Research registration unique identifying number (UIN)

Not applicable.

Guarantor

Guangchao Cao.

Provenance and peer review

Not commissioned, externally peer-reviewed.

Data availability statement

Data sharing does not apply to this study, as no datasets were generated or analyzed during the current study.