Acute Knee Injuries

Anterior cruciate ligament Injury:
The most disabling knee injury for a sportsperson involved in pivoting and turning activities e.g. basketball, netball, football, hockey.

The ACL is intracapsular, covered by synovium and positioned within the intercondylar notch attaching proximally on the posterolateral femur with an oval-shaped 2cm attachment and fans out in three bands to attach distally on the tibial spine. The three bands of the ligament (anterolateral, intermediate and posterolateral) are taught in different degree of knee flexion.

Functions and injury occurrence

  • It screws home the tibia on the femur by external rotation of the tibia on the femur as the knee extends
  • In the sidestep, excessive internal rotation of the tibia occurs and the ACL is tightened. In this position the ACL is most commonly torn. Any forces acting against the screw home mechanism compound the tear of the ACL
  • The second important function is to resist anterior displacement of the tibia on the femur.
  • In netball, sudden stoping forces the femur to slide forward over the tibia due to momentum of the upper body with the foot and tibia fixed to the ground

Other causes of injury:

  • An external tibial rotation force which causes a third degree tear of the tibial collateral ligament followed by a rupture of the ACL
  • A direct anterior draw, particularly of assisted by a quadriceps contraction, such as a skier falling backwards
  • A Varus (causing a bow legged stance) force applied to the inside of the knee resulting in disruption of the lateral capsular structures, the fibular collateral ligament and the ACL
  • A hyperextension force which causes disruption of the ACL first and then the posterior cruciate ligament

The majority of persons, who present with an ACL tear state they turned, pivoted or landed from a jump with a subsequent giving away.


  • Painful knee
  • Loss of knee extension due to the bundle of the ACL within the intercondylar notch that produces a “soft end feel”
  • Tenderness that is most obvious due to lateral capsular tearing or lateral meniscus damage
  • Tenderness along the medial joint line usually indicates an associated medial meniscus tear

Posterior cruciate ligament:


  • The PCL is intra-articular but extrasynovial
  • Is twice as strong as the ACL, works reciprocally with the ACL, and is tightest in the mid ranges of motion
  • Because of its fan-shaped insertion some parts of it are tight during each degree of knee motion
  • It becomes tighter with internal rotation of the tibia and it resists an anterior slide of the femur when the athlete is weight-bearing
  • The PCL resists hyperextension and contributes to medial stability of the knee


  • Intensive strengthening of the quadriceps and improved flexibility of the hamstrings are important in the rehab process before a gradual return to participation

Medial Collateral

Mechanisms of injury:

  • The two fundamental mechanisms of injury to the MCL are a direct valgus force applied to the knee and an external tibial force or a combination of these usually
  • The lateral meniscus may also be damaged by compression as the femur causes a valgus compression during impact
  • Occurs when a rugby player is tackled from the side, two soccer players kicking the ball simultaneously, and a downhill skier catching the inside edge of the ski
  • Return to training can occur when there is:
  1. Full ROM
  2. Full strength and proprioception function
  3. Minimal ligament tenderness
  4. Minimum symptoms
  5. Pain-free at the endpoints of knee joint movement
  6. Confident pain free running and change of direction


Some relevant strengthening

  • Balance exercises (single leg standing) for proprioception and knee stabilization (balance board or balance pad)
  • Wobble board in later stages of recovery as knee stabilizes
  • Unloaded knee bends (passive) then gradually increased the level of weight bearing
  • Hip lifts: lying supine load the affected leg with about 90° flexion. Extend the other leg off the ground and hold for 6 seconds
  • Knee bends with loading: Start with body weight (supported if necessary with a brace) then progress to ½ squats with gradually increasing weight (pain free)
  • Step-ups: stand on healthy leg and ascend a step gently on the affected leg. Increase reps as permitted pain free. Start with a step that is not very high
  • Step-downs: as above but obviously descending a step
  • Hamstrings standing hip extension against resistance: Standing on healthy leg work with affected leg.
  • Hamstrings: resisted sitting knee flexion
  • Straight line running
  • Straight line sand running on level sections i.e. not on a camber. Increased co-contraction about the knee when running on sand should create an added strengthening stimulus to the supporting structures about the knee

Lateral Collateral Ligament: 

  • The LCL (Fibula Collateral) provides resistance to varus stress on the knee and is usually more lax than the medial ligament
  • An LCL tear is rare and is usually caused by a direct varus force
  • 1st and 2nd degree tears are treated similar to MCL tears. 3rd degree tears are more problematic and are usually associated with ACL rupture

Rehab of LCL tears:

  • Similar to that for MCL tears except that a brace or tape is placed to support the lateral aspect of the knee

Meniscal Tears:

  • One of the most commonly injured parts of the knee
  • Meniscus helps the knee joint to carry weight, glide and turn in many directions. It also reduces friction between the femur and tibia
  • Meniscal tears often result from twisting the knee, pivoting, cutting or deceleration and often occurs in conjunction with other injuries such as ACL tear


  • Stiffness and swelling
  • Tenderness in the joint line
  • Collection of fluid
  • Catching or locking of the knee
  • Knee buckling


  • The principles of rehabilitation are generally the same as for MCL and LCL injuries
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Malcolm Calcutt

In the last century, a mechanical fitter by trade. Now re-invented as a Soft Tissue Therapist that uses past skill sets to enable better understanding of your presentation. Loving the ability to have a difference in peoples lives through greater awareness and education. Quiet time is traveling, exploring our past around the world, Antiquities hold so much lost knowledge and understanding about being human.
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