Subchondral Insufficiency Fracture in the Elderly: A Radiologic and Clinical Review Based on a Case Study

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 Subchondral Insufficiency Fracture in the Elderly: A Radiologic and Clinical Review Based on a Case Study

노인의 연골하 부전 골절: 증례 연구를 기반으로 한 방사선학적 및 임상적 고찰

Introduction

Knee pain is a common presenting symptom in elderly individuals, often attributed to osteoarthritis or meniscal injuries. However, subchondral insufficiency fracture (SIF) represents an underrecognized but critical cause of acute knee pain, particularly in postmenopausal women. SIF occurs due to stress on weakened subchondral bone, usually in the context of osteopenia or osteoporosis. This post presents a detailed case of a 66-year-old woman with subchondral insufficiency fracture of the medial femoral condyle (MFC), explores radiological findings, differential diagnosis, and clinical implications, and includes quizzes for academic engagement.

Case Overview

Patient: 64-year-old female
Chief Complaint: Acute right knee pain after twisting injury
History: Sudden severe pain exacerbated by movement
Imaging: Plain radiographs and MRI of the right knee

Radiographic Findings

Figure 1. Anteroposterior and Lateral Knee Radiographs

Mild sclerosis of the medial femoral condyle with small joint effusion. No obvious fracture line.

→ Suggestive of subtle findings requiring further evaluation with MRI.

MRI Findings

MRI was crucial in identifying the pathology, especially given the limitations of radiography in early-stage subchondral fractures.

Figure 2. Proton Density Fat-Saturated Sagittal MRI

Curvilinear subchondral low-signal line at the weight-bearing surface of the medial femoral condyle with adjacent bone marrow edema.

Figure 3. T2-weighted Coronal SPACE MRI

Fluid-filled cleft adjacent to the subchondral plate indicates subchondral collapse and cartilage disruption.


Diagnostic Summary

MRI demonstrated the following:

  1. Primary lesion: SIF at the weight-bearing surface of the medial femoral condyle with subchondral collapse and extensive marrow edema.

  2. Secondary lesion: Small SIF at the central and posterior tibial plateau with mild surrounding edema.

  3. Cartilage: Full-thickness loss at the MFC and tibial plateau.

  4. Meniscus: Extrusion due to posterior horn tear (not shown).

  5. Ligaments: High-grade sprain to partial tear of the medial collateral ligament (MCL).

Pathophysiology

Subchondral insufficiency fractures result from repetitive stress on subchondral bone that is structurally weakened, often due to osteoporosis or abnormal biomechanics. In the elderly, particularly postmenopausal women, decreased bone mineral density plays a crucial role.

Mechanism:

  • Repetitive microtrauma on weakened subchondral bone.

  • Impaired bone remodeling → fracture formation.

  • Possible progression to articular surface collapse and secondary osteoarthritis if untreated.

Differential Diagnosis

ConditionDistinguishing Features
OsteoarthritisJoint space narrowing, osteophytes
Osteonecrosis (AVN)Geographic necrosis, double-line sign on MRI
Transient Bone Marrow Edema SyndromeSelf-limiting, no fracture line
Osteochondral FractureYounger age, associated with trauma
SIFCurvilinear low-signal line, marrow edema

Prognostic Indicators

Poor prognostic signs for SIF progression include:

  • Fluid-filled subchondral cleft

  • Subchondral collapse

  • Full-thickness cartilage loss

  • Meniscal extrusion

  • Low-signal fracture line > 1 cm

Management Strategy

Conservative:

  • Protected weight bearing

  • NSAIDs

  • Osteoporosis treatment

  • Close imaging follow-up

Surgical (in case of failure):

  • Unicompartmental knee arthroplasty (UKA)

  • High tibial osteotomy

  • Total knee replacement (TKR)

Quiz

1: Which subtle radiographic component may require further imaging?

(1) Inferior pole of the patella
(2) Medial femoral condyle
(3) Medial epicondyle
(4) Tibial tuberosity
(5) Quadriceps tendon

2: A curvilinear low signal along the MFC subchondral bone is:

(1) False
(2) True

3: Which structure is also damaged in this case?

(1) Medial tibial plateau
(2) Medial meniscus
(3) Medial collateral ligament
(4) All of the above

4: Which finding is a poor prognostic indicator?

(1) Extensive bone marrow edema
(2) Meniscal extrusion
(3) Subchondral cleft filled with fluid
(4) Subchondral fracture line > 1 cm
(5) All of the above

5: Which mechanism can cause osteochondral lesions?

(1) Acute trauma
(2) Avascular necrosis
(3) Subchondral bone weakening
(4) All of the above

Answer & Explanation

1. Answer: (2) Explanation: Subtle sclerosis at the MFC raises suspicion for an underlying subchondral lesion.

2.  Answer: (2) True Explanation: It represents a hallmark MRI finding of subchondral insufficiency fracture.

3.  Answer: (4) Explanation: MRI reveals SIF in the tibial plateau, meniscal extrusion, and MCL strain.

4. Answer: (5) Explanation: All represent signs of subchondral plate collapse and joint degeneration.

5.  Answer: (4) Explanation: All mechanisms contribute to osteochondral injury patterns.

Conclusion

Subchondral insufficiency fracture should be considered in elderly patients presenting with acute knee pain, especially in the absence of trauma history or obvious osteoarthritic change. MRI is the gold standard for early diagnosis, and recognition of poor prognostic signs can help guide therapeutic decisions. Prompt diagnosis and appropriate management can prevent progression to irreversible joint destruction.

References

  1. A. Yamamoto and S. Bullough, “Subchondral insufficiency fractures of the femoral head and knee: a review,” Radiology, vol. 264, no. 3, pp. 732–743, 2012.

  2. B. D. Miller, L. J. Staron, and D. S. Feldman, “Subchondral insufficiency fractures of the knee,” AJR Am J Roentgenol, vol. 197, no. 5, pp. 1190–1196, 2011.

  3. C. T. Mandell et al., “MRI of the knee: detailed assessment of subchondral bone,” Radiol Clin North Am., vol. 58, no. 5, pp. 933–951, 2020.

  4. J. C. Hayes and K. J. Mont, “Management of subchondral insufficiency fracture of the knee in elderly women,” Clin Orthop Relat Res., vol. 472, no. 12, pp. 3597–3605, 2014.

  5. N. Theodorou et al., “Subchondral insufficiency fractures of the knee: MRI features,” Skeletal Radiol., vol. 43, no. 5, pp. 611–617, 2014.

  6. K. Nishii et al., “MR imaging of subchondral insufficiency fracture of the femoral condyle,” Radiographics, vol. 27, no. 4, pp. 1111–1120, 2007.

  7. T. Yamamoto, “Subchondral insufficiency fracture of the knee: a preventable cause of secondary osteoarthritis,” Clin Orthop Surg., vol. 7, no. 2, pp. 206–211, 2015.

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