Clicking Knee After Bilateral TKA: Differential Diagnosis and Management
Initial Diagnostic Approach
Begin with weight-bearing plain radiographs (AP, lateral, and axial views) of the left knee to evaluate for aseptic loosening, component malposition, polyethylene wear, osteolysis, or periprosthetic fracture, as these are the most common causes of late pain and mechanical symptoms after TKA. 1, 2
Key Clinical Characterization
- Characterize the pain pattern precisely: Pain on weight-bearing suggests aseptic loosening or component wear, while night pain or pain at rest raises concern for infection 1, 2, 3
- Assess for infection signs: Warmth, erythema, fever, or systemic symptoms warrant immediate infection workup via joint aspiration, as periprosthetic infection requires urgent management 1, 2
- Document crepitus characteristics: Note whether clicking occurs with specific movements, is associated with catching/locking sensations, or causes functional limitation 1
Differential Diagnosis
Most Likely Diagnoses (3 Years Post-TKA)
Patellofemoral crepitus is the most common cause of clicking in posterior-stabilized TKA, occurring in 14-23% of cases, with only 4-6% being symptomatic 4, 5. This is particularly relevant if the patella was not resurfaced, as non-resurfaced knees have a 23.1% crepitus rate versus 7.3% in resurfaced knees 5.
Aseptic loosening is the leading cause of late TKA failure (39.9% of revisions), often presenting with mechanical symptoms including clicking, and frequently coexists with osteolysis 1, 2
Polyethylene liner wear can produce clicking sounds and is detectable on radiographs when measuring liner thickness 1
Patellar complications including subluxation, component loosening, or impingement occur in 3.6% of cases and can manifest as clicking 1
Less Common but Important Diagnoses
- Meniscal pathology: Retained meniscal tissue or tears are associated with crepitus in native knees 6
- Component malrotation: Internal rotation of components causes patellofemoral tracking abnormalities and clicking 1
- Periprosthetic infection: Occurs in 0.8-1.9% of TKAs and can present with mechanical symptoms before systemic signs develop 1
- Patellar clunk syndrome: Fibrous nodule formation in the suprapatellar pouch causing catching 1
Diagnostic Algorithm
Step 1: Plain Radiographs (Rating 9/9)
Obtain weight-bearing AP, lateral, and axial views to assess: 1, 2
- Component positioning and alignment
- Progressive lucencies >2mm at bone-cement or cement-prosthesis interface
- Osteolysis (focal bone loss)
- Polyethylene liner thickness and wear
- Patellar tracking and positioning
- Heterotopic ossification
Step 2: Advanced Imaging Based on Radiographic Findings
If radiographs show lucencies, osteolysis, or component malposition: CT knee without IV contrast (Rating 8/9) is preferred for quantifying osteolysis and assessing the bone-implant interface 1, 2
If component rotation is suspected: CT without IV contrast (Rating 9/9) is the imaging modality of choice for measuring rotational alignment 1
If soft-tissue pathology is suspected (patellar tendon, quadriceps tendon, or impingement): MRI without IV contrast (Rating 7/9) or ultrasound (Rating 7/9) are equivalent options 1
If infection cannot be excluded clinically: Proceed to joint aspiration for cell count, culture, and sensitivity; obtain ESR and CRP (CRP >13.5 mg/L has 73-91% sensitivity) 1, 2
Step 3: Specialized Studies if Diagnosis Remains Unclear
Fluoroscopy (Rating 7/9) can demonstrate dynamic instability or abnormal patellar tracking during movement 1
Avoid routine bone scans: Positive bone scans occur in 12.5% of asymptomatic knees at 2 years post-TKA, making interpretation difficult 2
Treatment Approach
Conservative Management (First-Line for Benign Crepitus)
For asymptomatic or minimally symptomatic clicking without radiographic abnormalities: 4, 5
- Reassurance that crepitus alone does not require intervention
- NSAIDs for inflammation control if pain is present 2
- Physical therapy focusing on quadriceps strengthening and patellar tracking exercises 2
- Activity modification to avoid provocative movements
Interventional Management
If conservative treatment fails after 3 months or radiographs show concerning findings: Refer back to orthopedic surgery for evaluation 2
For symptomatic patellar crepitus with impingement: Arthroscopic debridement of fibrous nodules may be indicated 1
For component malrotation or instability: Revision TKA may be necessary 1
For confirmed aseptic loosening or significant wear: Orthopedic surgery referral for revision consideration 2, 3
For periprosthetic infection: Urgent surgical intervention with two-stage revision is typically required 1
Critical Pitfalls to Avoid
Do not dismiss clicking as benign without obtaining radiographs, as aseptic loosening can present with mechanical symptoms before pain becomes severe 1, 2
Do not assume all clicking is patellofemoral crepitus—polyethylene wear, component loosening, and infection must be excluded radiographically 1, 2
Do not delay surgical referral if pain is progressive, occurs at night/rest, or is associated with instability, as these suggest serious complications requiring intervention 1, 2, 3
Do not obtain MRI as first-line imaging—radiographs are always the initial study, with advanced imaging guided by radiographic findings 1
Follow-Up Recommendations
Annual weight-bearing radiographs are recommended for detecting subclinical wear and osteolysis, even in asymptomatic patients 2
Serial radiographs every 6-12 months if initial films show borderline lucencies or early osteolysis to monitor progression 1, 2