Femoral neck stress fractures (FNSFs) are rare but potentially serious injuries caused by repetitive subthreshold loading that exceeds the bone’s capacity for remodeling. Although commonly reported in athletes and military personnel, they may also occur in the general population without obvious predisposing factors [1].

FNSFs are frequently underdiagnosed because of their insidious onset and nonspecific presentation. Patients commonly report groin or hip pain; however, referred pain to the thigh or knee may occur and contribute to diagnostic confusion [2]. Occult fractures, defined as fractures not visible on plain radiographs, further complicate early diagnosis and often require advanced imaging modalities such as magnetic resonance imaging (MRI) for confirmation [3].

In primary care settings, isolated knee pain is often attributed to local pathology, potentially delaying recognition of proximal causes. Failure to diagnose FNSFs early may result in fracture displacement, nonunion, or avascular necrosis of the femoral head [4]. This case report describes an unusual presentation of an occult femoral neck stress fracture manifesting solely as knee pain and emphasizes the importance of comprehensive clinical assessment and appropriate imaging.

A 35-year-old previously healthy male presented to the family medicine clinic with a 2-week history of progressive right knee pain. The pain was insidious in onset, worsened with weight-bearing, and was not associated with trauma, swelling, locking, or instability. Initial differential diagnoses included patellofemoral pain syndrome, meniscal pathology, tendinopathy, early degenerative disease, and referred pain from the hip or lumbar spine. The patient reported recent increased physical activity related to manual labor but denied participation in sports.

The patient denied smoking, excessive alcohol consumption, corticosteroid use, prior stress fractures, endocrine or metabolic bone disease, nutritional deficiencies, or recent weight loss. There was no known history of osteoporosis or chronic systemic illness.

Physical examination demonstrated a normal right knee with full range of motion, no effusion, no joint-line tenderness, and no ligamentous instability. However, discomfort was elicited during internal rotation of the right hip, raising suspicion for a proximal source of pain and prompting extension of the diagnostic workup to the hip. Neurovascular examination was otherwise unremarkable.

Initial plain radiographs of the right knee were normal. Conservative management with nonsteroidal anti-inflammatory drugs (NSAIDs), activity modification, and rest was initiated.

Due to persistent symptoms after 10 days and lack of clinical improvement, further evaluation was undertaken. Radiographs of the pelvis and hip were inconclusive and showed no visible fracture. Because persistent symptoms and hip examination findings remained unexplained despite negative radiographs, MRI was obtained as the preferred imaging modality for suspected occult femoral neck stress fractures due to its high sensitivity for early bone stress injury and bone marrow edema [5][7].

MRI of the right hip revealed a nondisplaced inferomedial (compression-side) femoral neck stress fracture associated with surrounding bone marrow edema [5].

Figure 1. Coronal fat-suppressed T2-weighted MRI of the right hip demonstrating a linear hypointense fracture line (red arrow) at the superolateral aspect of the femoral neck with surrounding bone marrow edema (white arrow), consistent with an occult nondisplaced femoral neck stress fracture.

Following diagnosis, the patient was urgently referred to orthopaedics (see Figure 1Figure 1). Management consisted of strict non-weight-bearing with crutches for 6 weeks and serial clinical and radiographic follow-up. Repeat radiographs obtained at 6 weeks demonstrated interval fracture healing without displacement. Progression to partial and subsequently full weight-bearing was guided by complete resolution of pain during ambulation and evidence of radiographic healing. Surgical intervention was not required because the fracture remained stable throughout follow-up.

At 3-month follow-up, the patient had resumed normal daily activities without pain or functional limitation.

Occult femoral neck stress fractures may rarely present with atypical symptoms such as isolated knee pain, potentially delaying diagnosis. Clinicians should consider proximal pathology when persistent symptoms and examination findings are not adequately explained by knee pathology alone.

MRI is particularly valuable when ongoing symptoms and clinical suspicion raise concern for an occult proximal source despite negative radiographs. Early recognition and appropriate multidisciplinary management are essential to prevent complications and optimize patient outcomes.

This report describes a single clinical case, limiting the generalizability of the findings. In addition, long-term follow-up was not available to evaluate for late complications such as avascular necrosis or recurrent stress injury.

No external funding was received for this study.

Written informed consent was obtained from the patient for publication of this case report and accompanying images. Ethical approval was not required according to institutional guidelines for single case reports.

[Sandy M]: Conceptualization, patient evaluation, manuscript drafting.

[Zayd A]: Orthopaedic management, literature review, manuscript revision.

No artificial intelligence tools were used in the preparation of this manuscript.