What causes severe pain in the medial malleolus after total knee joint replacement?

Severe Medial Malleolus Pain After Total Knee Replacement

Your severe medial malleolus pain after total knee arthroplasty is most likely unrelated to the knee replacement itself and represents a separate ankle pathology that requires distinct evaluation—begin with plain radiographs of the ankle (not just the knee) and consider stress fracture, accessory ossicle, or referred pain from component malrotation as potential causes.

Why the Medial Malleolus is Affected

The medial malleolus is anatomically distant from the knee joint, making direct surgical trauma unlikely. However, several mechanisms can explain your pain:

Altered Gait Mechanics Post-TKA

• Component malrotation (particularly excessive internal rotation of tibial or femoral components) can alter lower extremity biomechanics and create abnormal stress patterns at the ankle 1
• Compensatory gait changes during recovery from TKA can overload the medial ankle structures, potentially causing stress fractures 2, 3
• The medial malleolus is particularly vulnerable to stress fractures from repetitive loading, though these are rare in non-athletes 2, 4

Coincidental Ankle Pathology

• Accessory ossicles (os subtibiale) at the medial malleolus can become symptomatic and cause severe pain, mimicking fracture 5, 6
• These may be pre-existing but become symptomatic due to altered mechanics post-TKA 5
• Stress fractures of the medial malleolus present with localized pain that worsens with weight-bearing 2, 3, 4

Immediate Diagnostic Approach

First-Line Imaging

• Obtain plain radiographs of the ankle specifically, not just the knee—standard knee radiographs will not adequately visualize the medial malleolus 7, 8
• Look for vertical fracture lines, accessory ossicles, or bone abnormalities at the medial malleolus 2, 3
• Critical pitfall: Initial radiographs are frequently normal in medial malleolar stress fractures because the medial malleolus consists mainly of cancellous bone 3, 4

If Radiographs Are Negative But Pain Persists

• MRI of the ankle without contrast is the gold standard for detecting medial malleolar stress fractures, showing bone marrow edema even when radiographs are normal 2, 3, 4
• MRI will also identify soft tissue abnormalities, ligament injuries, or inflammatory changes 3
• CT can reveal subtle fracture lines or accessory ossicles not visible on plain films 5, 3, 6

Evaluate the Knee Component Positioning

While addressing the ankle pain, assess whether TKA component malrotation is contributing:

Component Rotation Assessment

• CT of the knee without IV contrast is the most accurate method for measuring component rotation if malrotation is suspected 1
• Excessive combined internal rotation of tibial and femoral components correlates with altered biomechanics and potential downstream effects 1
• The femoral component should be parallel to the transepicondylar axis, and the tibial component should be positioned in approximately 18 degrees of internal rotation relative to the tibial tubercle 1

Management Based on Findings

If Stress Fracture Is Confirmed

• Surgical treatment with internal fixation (tension band wiring) results in rapid healing (3-4 months) and return to activity, particularly important if you wish to maintain mobility 2, 3
• Conservative management with protected weight-bearing can be attempted but may prolong recovery 4
• Early surgical intervention should be strongly considered to prevent prolonged disability 2

If Accessory Ossicle Is Symptomatic

• Arthroscopic resection of the ossicle effectively relieves symptoms with minimal deltoid ligament damage and allows return to full activity within 3 months 6
• Conservative treatment often fails for symptomatic ossicles 6

If Component Malrotation Is Contributing

• Referral back to orthopedic surgery for evaluation of revision TKA may be necessary if malrotation is severe and causing persistent biomechanical problems 1

Critical Pitfalls to Avoid

• Do not assume the ankle pain is related to the knee surgery without proper ankle-specific imaging 2, 5
• Do not rely solely on plain radiographs—MRI is essential if clinical suspicion for stress fracture is high despite negative X-rays 2, 3, 4
• Do not delay diagnosis—medial malleolar stress fractures are often missed initially, leading to prolonged disability and treatment complications 2, 3
• Do not confuse accessory ossicles with acute fractures—comparison views of the contralateral ankle can help differentiate congenital variants from traumatic injuries 5