Soft Tissue Injuries of the Knee
Soft tissue injuries of the knee commonly involve the:
- Anterior cruciate ligament (ACL)
- Posterior cruciate ligament (PCL)
- Medial collateral ligament (MCL)
- Lateral collateral ligament (LCL)
- Menisci
Key anatomy:
| Structure | Main function |
|---|---|
| ACL | Prevents anterior translation of the tibia on the femur and contributes to rotational stability |
| PCL | Prevents posterior translation of the tibia on the femur |
| MCL | Resists valgus stress, preventing the knee from opening medially |
| LCL | Resists varus stress, preventing the knee from opening laterally |
| Menisci | Fibrocartilage structures that improve joint movement, shock absorption, and load distribution |
Recognition – Comparison Table
| Injury | Typical mechanism | Typical symptoms | Key examination finding | |
|---|---|---|---|---|
| ACL injury |
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| PCL injury | Direct blow to proximal tibia with knee flexed, such as:
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| MCL injury |
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| LCL injury |
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| Meniscal injury |
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The unhappy triad refers to combined injury of the following 3 structures:
- ACL
- MCL
- Meniscus
Investigation and Diagnosis
| Investigation | Indications | Purpose |
|---|---|---|
| X-ray | Use the Ottawa knee rule to determine whether an X-ray is needed
As per the rule, a knee X-ray is only indicated if ANY of the following is present:
|
Assess for fracture or dislocation |
| MRI knee | MRI is the imaging of choice for internal soft tissue injury (i.e. suspected cruciate ligament injury, meniscal tear) | To confirm soft tissue injury and guide management |
Management
Initial Management
Most suspected knee soft tissue injuries can be managed initially using the PRICE approach:
| PRICE component | Description |
|---|---|
| Protection | Protect the knee from further injury, such as:
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| Rest | Relative rest is preferred over complete immobilisation for a prolonged period |
| Ice | Apply ice wrapped in a damp towel for 15-20 minutes every 2-3 hours during the day
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| Compression | Use a simple elastic bandage or an elasticated tubular bandage to control swelling (remove before going to sleep) |
| Elevation | Elevate the leg above heart level where possible, until the swelling is controlled |
Definitive Management
Definitive management usually involves either:
- Conservative management with physiotherapy and rehabilitation
- Operative management (commonly arthroscopically)
- Options for cruciate ligament injury: reconstruction / repair
- Options for meniscal tear: repair / menisectomy
Generally, operative management is considered when there is:
- High functional demand (e.g. professional athlete)
- Complete ligament rupture / tear
- Displaced meniscal tear
- Multiple ligament involvement
- Failure of conservative management