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Acute knee injuries



What is it?


The knee joint is designed to flex or extend only, with no rotation. It consists of three bones (thigh, leg and knee cap). The cruciate ligaments provide fore-aft stability and the collateral ligaments side-to-side stability. The knee cap is connected to the thigh muscles and helps in the action of straightening a bent knee. The two menisci (medial and lateral) are cartilages which provide padding between the thigh and leg bones.


Cruciate ligament injuries tend to occur with sudden force acceleration or deceleration injuries. Collateral ligament injuries occur with side bending injuries of the knee. Meniscal injuries occur in combined knee flexion and rotation movements. Patella injuries occur as a result of a blow to the point of the knee or with repetitive squatting or climbing. Severe knee injuries can result in a combination of crucial, collateral and meniscal injuries occurring at the same time.


Pre-patella Bursitis (“Housemaids Knee”) occurs in workers who crawl a lot (for example roofers or carpet layers).






Injuries involving either fractures of bones, or rupture of the cruciate ligaments tend to swell rapidly (within minutes of the injury), and medical injuries tend to swell slowly (within hours of the injury).


In addition to pain and swelling other symptoms include instability, locking or giving way.




Knee injuries are common. In the aging work-force (particularly the obese) degenerative knee conditions (arthritis) are also common. A prior history of a menisectomy can also lead to knee arthritis.



Key Points


The history is important.  Issues to look for include:


  • Some tears require referral and possible arthroscopies

  • Early rehabilitation should be mandatory to reduce effusion

  • Physiotherapy also maximizes range of movement, allows early strengthening and proprioceptive retraining and return to work

  • Education about re-injury is important from GP or specialist

  • Lateral tears are rarer than medial tears



History (for meniscal tears) – (ACC recommended treatment profiles)


  • Swelling usually occurs greater than four hours after injury or the next day

  • Tears are usually associated with a twisting injury, flexed knee with fixed foot

  • Determine degree of force associated with injury, amount of mobility and whether there is associated locking or giving away.



History – Collateral ligament


  • Determine mechanism of injury, whether direct or indirect blow

  • Determine location of pain or tenderness

  • Determine whether there is loss of functions

  • Differential diagnosis

  • Torn cruciate ligament

  • Torn medial/collateral ligaments

  • Osteocondral fracture

  • Degenerative joint disease

  • Meniscal injury

  • Fracture


Recommended investigations (Collateral ligament)

  • X-rays if swollen for possible fracture


Severe trauma treatment (Collateral ligament)


  • Analgaesia

  • Physiotherapy

  • Tubigrip and crutches

  • RICE (Rest, Ice, Compression, Elevation)


For meniscal tear as above:


  • Gradual mobilisation

  • Passive quadriceps exercises





When to Consider Referral to a specialist


Issue to look for:


  • The presence of any red flag conditions

  • The worker has had more than two weeks certified unfit for duties, or more than one month on selected duties

  • The worker has had more than three weeks off work, or on selected duties and has significant yellow flag conditions

  • Not back at pre-injury duties within six weeks of the injury.



Red flag conditions:


  • Immediate onset of significant knee swelling

  • Significant trauma

  • Unstable knee

  • Recurrent locking or giving way

  • Fever

  • IV drug use

  • Steroid use

  • Severe unremitting night time pain

  • Patient aged over 50 years

  • Objective evidence of thigh muscle wasting (quadriceps or VMO)



Yellow flag conditions:


  • Attitudes and beliefs about pain

  • Emotions

  • Behaviour

  • Family

  • Compensation issues

  • Work

  • Diagnostic and treatment issues

  • Workplace conflict



Possible alternate duties:


  • No weight bearing with the affected leg

  • No overhand gripping with the affected knee

  • Maximum lift 5 kgs

  • No squatting or climbing

  • No prolonged walking or standing

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