Knee arthroplasty
Knee replacement and NSW CTP permanent impairment
Knee replacement is assessed by a point system, not a fixed surgical percentage. Clause 6.101 directs the assessor to Table 66, where some points are deducted before the result is converted through Table 64.
Motor accident injury
How can this injury happen?
Car or passenger collision
Severe plateau, femoral or patella injury may cause post-traumatic arthritis and later replacement.
Motorcycle accident
Complex fracture or cartilage damage after a motorcycle fall can lead to arthroplasty.
Pedestrian or cyclist impact
Direct knee trauma may eventually require replacement after fracture, instability or cartilage loss.
Injuries that can occur
- total or unicompartmental knee replacement
- revision arthroplasty
- replacement after post-traumatic arthritis
- post-operative stiffness, instability, infection or loosening
Symptoms and functional problems
- limited flexion or extension
- walking, stairs and transfer difficulty
- instability, swelling or persistent pain
- need for a walking aid or revision
Seek urgent medical assessment
Suspected infection, acute prosthetic instability, threatened circulation or inability to weight-bear requires urgent assessment.
Clinical evidence
What findings matter?
The Table 66 result uses the actual replacement outcome. Operative records, alignment, pain, function, stability and movement should be consistent with the point items.
| Record or examination | What it may establish | What it cannot prove alone |
|---|---|---|
| Table 66 clinical score | Applies the knee replacement point items and deductions. | Exact row points require the readable AMA4 table. |
| X-ray and operative record | Shows components, alignment, fixation and complications. | A well-positioned implant does not decide all functional points. |
| Movement, stability and walking evidence | Records the practical replacement result. | Do not add a separate gait or ROM percentage for the same outcome. |
Movement in daily life
How movement affects real activities
Replacement function includes flexion for sitting and stairs, extension for stable walking, and overall stability and walking tolerance. Table 66 integrates these rather than assigning WPI by surgery alone.
Flexion
Sitting, stairs and rising from a chair.
Measured as part of the replacement result, not duplicated under Table 41.
Extension
Stable standing and normal walking.
Fixed extension loss affects the Table 66 result.
Stability and walking
Safe community mobility and sustained weight bearing.
Aid use and functional evidence must be genuine and consistent.
Threshold injury is a separate question: replacement is treatment. Threshold classification depends on the underlying fracture, cartilage rupture or other accident-related injury.
Part 6 permanent impairment
How is CTP WPI assessed?
Clause 6.101 requires Table 66 for knee replacement. Unlike Table 65, some points are deducted in Table 66, and the total is converted to an impairment rating from Table 64.
Measurement rules that apply
- Clauses 6.69 and 6.70 require the method that most specifically addresses the lower-limb impairment. Gait should not replace a joint, nerve, fracture or replacement method that can be applied reliably.
- Clause 6.84 requires active range of motion, a goniometer where clinically indicated and consistent repetitions when reliability is uncertain. Passive movement may inform the examination but does not set the impairment value.
- Clause 6.85 says only the most severe deficit in one direction or axis from the same lower-limb ROM table is rated. Deficits from separate tables may be combined only as the Guidelines permit.
| Method | CTP source | When it is relevant | Important limit |
|---|---|---|---|
| Knee replacement point score | Clause 6.101; AMA4 Table 66 | Permanent result after knee arthroplasty. | Some points are deducted; exact rows require readable AMA4. |
| Conversion | Table 64 and Table 6.4 | Converts the Table 66 result to WPI. | Do not add surgery, gait or ROM again. |
| Permanence | Clauses 6.19-6.21 | Assessment after recovery is static or well stabilised. | Pending revision may make assessment premature. |
- Use the actual post-treatment result.
- Document complications and revision plans.
- Do not assume all total or partial replacements have the same score.
What cannot be combined?
- Table 66 result with gait derangement
- separate Table 41 ROM for the same replaced knee
- surgery or pain as extra values
What does not establish WPI by itself?
- operation name
- implant X-ray
- pain score
- walking aid alone
Motor accident examples
Replacement after tibial plateau fracture
The Table 66 result assesses the current replaced knee; the historical fracture is not added again for the same impairment.
Replacement with revision recommended
If the result may change substantially after revision, permanence must be considered before assessment.
Claim file preparation
Evidence checklist
Assessment source
Knee replacement WPI source
Assessment source: Motor Accident Guidelines v10.1 clauses 6.19-6.21 and 6.101; AMA4 Tables 66 and 64; Table 6.4 conversion.
Threshold injury: Replacement is treatment; threshold status follows the underlying accident-related injury.
What the assessor checks
- Table 66 point system
- deduction rule
- Table 64 conversion
- no fixed surgical value
What does not establish the result by itself
- surgery
- implant
- pain
- aid use
Official sources
Related NSW CTP guides
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Frequently asked questions
- Does knee replacement have fixed WPI?
- No. Clause 6.101 requires the actual result to be scored under Table 66.
- Are all Table 66 points added?
- No. Clause 6.101 says some points are deducted when Table 66 is used.
- Can knee ROM be added?
- Not when it duplicates the replacement result.
- Can gait be combined?
- No. Gait derangement cannot be combined with another lower-limb evaluation.
- Does revision surgery matter?
- It may affect permanence and the eventual result, but it does not create an automatic percentage.