Avulsion Fracture at the Femoral Origin of the Medial Head of the Gastrocnemius in an Adolescent: A Case Report with Two-Year Clinical Follow-Up

Abstract

Avulsion fractures at the femoral origin of the medial head of the gastrocnemius are exceptionally rare, particularly in skeletally immature patients, and may be overlooked when evaluating acute posterior knee pain. A previously healthy 13-year-old boy developed acute posteromedial left knee pain and felt a sudden pop while running. He could bear weight with difficulty and held the knee in slight flexion because terminal extension was painful. Examination showed focal posteromedial tenderness, preserved motion with pain at full extension, and an intact distal neurovascular status. Plain radiographs demonstrated a small osseous fragment posterior to the distal femur. Magnetic resonance imaging (MRI) identified a 1.2 × 0.5 cm minimally displaced, partially corticated fragment arising from the femoral origin of the medial head of the gastrocnemius, with no associated ligamentous, meniscal, or musculotendinous injury. The patient was managed with a long-leg cast at 30° of knee flexion for six weeks, followed by six weeks of supervised range-of-motion, stretching, and strengthening exercises. He regained painless full range of motion, normal strength on clinical examination, and a stable knee, and subsequently returned to sports without reported pain or functional limitation. At two-year clinical follow-up, he remained asymptomatic without instability or treatment-related complications. This case adds to the limited pediatric literature on this uncommon injury and highlights the role of MRI in characterizing the lesion and excluding associated injuries. Because no follow-up imaging was obtained, the outcome represents clinical recovery rather than radiographically confirmed osseous union.

Introduction

Injuries of the medial gastrocnemius most commonly involve the musculotendinous junction, whereas avulsion of a bone fragment from its femoral origin is distinctly uncommon. Only a small number of isolated cases have been described, and pediatric evidence remains limited.^1–6 Because symptoms overlap with meniscal, ligamentous, hamstring, and proximal gastrocnemius injuries, a subtle fragment posterior to the distal femur may be missed on initial radiographs.^2,3

We present an additional pediatric case of an isolated, minimally displaced osseous lesion at the femoral origin of the medial head of the gastrocnemius. Given the small number of reported pediatric cases, this report contributes further clinical and imaging detail regarding presentation, diagnostic evaluation, conservative management, and long-term clinical outcome, without implying superiority of the specific immobilization protocol used.

Case Report

A previously healthy 13-year-old boy presented to the pediatric orthopedic clinic with acute pain in the posterior aspect of his left knee after an injury while running during sports. He reported a sudden pop without a direct blow or fall and was unable to continue the activity. There was no locking or giving way.

He could bear weight with difficulty and preferred to keep the knee slightly flexed because terminal extension aggravated the pain. Examination demonstrated a mild antalgic gait and focal tenderness over the posteromedial distal femur, corresponding to the femoral origin of the medial head of the gastrocnemius. There was no gross deformity or substantial swelling. Active and passive knee motion were preserved, although full extension caused marked pain. Ligamentous testing was limited by pain, but no gross instability was appreciated. Motor and sensory examination was normal, and distal pulses were palpable.

Plain anteroposterior and lateral radiographs of the left knee demonstrated a small osseous fragment adjacent to the posterior distal femur, raising suspicion for an avulsion injury (Figure 1). MRI showed a 1.2 × 0.5 cm partially corticated osseous fragment with minimal posterior displacement arising from the femoral origin of the medial head of the gastrocnemius (Figure 2). No associated injury of the cruciate or collateral ligaments, menisci, physis, or adjacent musculotendinous structures was identified.

Figure 1.

Plain radiographs of the left knee. (A) Anteroposterior view. (B) Lateral view demonstrating a small osseous fragment adjacent to the posterior aspect of the distal femur (arrow), suspicious for an avulsion injury.

Figure 2.

Magnetic resonance images of the left knee. (A and B) Selected sequences demonstrate a 1.2 × 0.5 cm minimally posteriorly displaced, partially corticated osseous fragment (arrow) arising from the femoral origin of the medial head of the gastrocnemius. No associated ligamentous, meniscal, physeal, or musculotendinous injury is identified.

Given the minimal displacement, absence of associated injury, and lack of clinical instability, non-operative treatment was selected. The knee was immobilized in a long-leg cast at 30° of flexion for six weeks. Protected weight-bearing and avoidance of sports were advised during immobilization.

After cast removal, the patient completed six weeks of supervised physiotherapy comprising progressive range-of-motion exercises, gastrocnemius and quadriceps stretching and strengthening, and gradual functional rehabilitation. At completion, he had painless full knee motion, restored strength on clinical examination, and a clinically stable knee. He subsequently returned to sports without reported pain or functional limitation. The competitive or recreational level of participation, formal return-to-sport testing criteria, exact timing of return beyond completion of the treatment course, and confirmation of return to the exact pre-injury performance level were not prospectively documented. At two-year clinical follow-up, he remained asymptomatic with full knee motion and no reported instability, recurrent symptoms, or treatment-related complications; continued participation at the same level was not specifically documented.

Discussion

This case demonstrates that an adolescent with an isolated, minimally displaced osseous lesion at the femoral origin of the medial gastrocnemius can achieve a favorable long-term clinical outcome following non-operative management. The central clinical lessons are to consider this injury in a young athlete with acute posteromedial knee pain, obtain MRI when radiographs show a subtle posterior femoral fragment or symptoms remain unexplained, and base management on displacement, stability, and associated injury.

The proposed mechanism is sudden traction at the femoral attachment during eccentric gastrocnemius loading, often with knee extension and rotational stress.^1–3 In the immature skeleton, the developing osseous attachment may fail before the tendon or musculotendinous junction. Our patient’s injury while running, without direct impact, is consistent with an indirect traction mechanism.

An important imaging feature in this case was the partial cortication of the osseous fragment. Although the acute onset of posteromedial knee pain with a sudden pop during running and focal tenderness at the medial gastrocnemius origin supported an acute traction-related event, partial cortication raises the possibility that at least part of the fragment represented pre-existing ossification or a chronic traction-related process. In the absence of pre-injury imaging, the chronicity of the osseous component cannot be established with certainty. Accordingly, the imaging appearance should be interpreted in conjunction with the acute clinical presentation rather than considered definitive evidence that the entire fragment developed acutely.

Diagnosis may be difficult because examination findings are nonspecific and pain may prevent reliable stability testing. Radiographs may reveal only a small posterior femoral fragment or may initially appear normal.^2,3 MRI defines the attachment of the gastrocnemius tendon to the fragment, characterizes displacement, and evaluates the menisci, ligaments, physis, and other soft tissues. In the present case, MRI confirmed the diagnosis and, importantly, excluded injuries that would have altered management.

Published treatment has varied according to displacement and concomitant injury (Table 1). Maehara and Sakaguchi used open reduction and internal fixation for a displaced isolated fragment in an adult.¹ Hirotsu et al fixed the gastrocnemius and medial collateral ligament avulsions in a 15-year-old with posterior cruciate ligament injury.⁴ In contrast, Patterson et al, Naffaa et al, Ammann et al, and Carabajal-Mattar et al reported favorable outcomes after conservative treatment of isolated pediatric injuries.^2,3,5,6 These reports and the current case support non-operative care when the fragment is minimally displaced and the knee is stable after associated injuries have been excluded.

Table 1.

Published Cases Relevant to Avulsion Fracture of the Femoral Origin of the Medial Head of the Gastrocnemius

Report	Patient/Injury	Associated Injury	Treatment	Outcome
Maehara and Sakaguchi, 20041	26-year-old adult; displaced isolated fracture	None reported	ORIF	Good clinical outcome
Patterson et al, 20142	14-year-old male wrestler; minimally displaced/occult	None	Conservative	Pain-free; returned to wrestling at 8 weeks
Naffaa et al, 20183	13-year-old boy; skiing injury; <4 mm displacement	None	Brace and physiotherapy	Full motion; pain resolved
Hirotsu et al, 20194	15-year-old boy; contact soccer injury	PCL injury and femoral MCL avulsion	Operative fixation	Returned to sport; mild residual posterior laxity
Ammann et al, 20255	12-year-old girl; slightly displaced isolated fracture	None	Activity restriction and physiotherapy	Pain-free return to recreational sport at 10 weeks
Carabajal-Mattar et al, 20256	12-year-old female gymnast; minimally displaced isolated fracture	None	Conservative	Returned to gymnastics; asymptomatic at 2 years
Present case	13-year-old boy; running injury; minimally displaced	None	Cast 6 weeks, then physiotherapy 6 weeks	Unrestricted sport; asymptomatic at 2 years

Abbreviations: MCL, medial collateral ligament; ORIF, open reduction and internal fixation; PCL, posterior cruciate ligament.

The present report documents one conservative approach—six weeks in a long-leg cast at 30° of flexion followed by six weeks of supervised rehabilitation—and a favorable two-year clinical outcome. This regimen should not be interpreted as superior to previously reported conservative approaches because no comparative evidence is available. Surgical fixation remains reasonable for substantial displacement, persistent instability, failure of conservative treatment, or associated multiligament injury. Because the evidence is limited to case reports, treatment should be individualized and future studies should standardize reporting of displacement, immobilization, rehabilitation, return-to-sport criteria, imaging follow-up, and long-term outcomes.

A further limitation is the absence of follow-up radiographs, CT, or MRI. Consequently, although the patient achieved complete clinical recovery, this report cannot establish osseous union, remodeling, persistence or change in displacement of the fragment, or the presence of fibrous union or nonunion. The findings should therefore be interpreted as evidence of a favorable clinical outcome rather than radiographically confirmed fracture healing.

Funding Statement

The author received no specific funding for this work.

Data Sharing Statement

All relevant clinical information is included in this report. Additional data are not publicly available to protect patient confidentiality.

Ethics Approval

Institutional ethical approval was required for publication of this case report and was obtained from the Institutional Review Board of Imam Abdulrahman bin Faisal University (Approval No. IRB-2026-01-0603).

Consent to participate

Consent to participate was obtained from the father as his legal guardian.

Consent for Publication

Written informed consent for the publication of clinical information and radiologic images was obtained from the patient’s father, his legal guardian.

Author Contributions

All authors made a significant contribution to the work reported, whether that is in the conception, study design, execution, acquisition of data, analysis and interpretation, or in all these areas; took part in drafting, revising or critically reviewing the article; gave final approval of the version to be published; have agreed on the journal to which the article has been submitted; and agree to be accountable for all aspects of the work.

Disclosure

The author declares no conflicts of interest.