How I Rehab: Common Deficits in ACL Rehabilitation with Luke Heath

July 2nd, 2024

Luke Heath is a Titled Sports and Exercise physiotherapist with extensive experience working in elite sport across AFL (GWS Giants), A-League (Sydney FC) and Australian Rugby Union. Luke is currently the senior physio in the knee department at Aspetar where he works with an experienced team of physiotherapists treating athletes ACL injuries

In his podcast with SportsMAP founder Nick Kane Luke discusses the 3 most common deficits he sees in ACL Rehabilitation and how he addresses these.

Deficit 1: Regaining Extension 

You must do the basics well. This is as basic as it gets. 

Regaining knee extension is very important within the first 6 weeks of rehab. From Day 1 post op it is important to decrease swelling and regain an active quad contraction. The sooner this is achieved, the better it is for your knee and recovery.  In this initial phase ‘the war is won at home’ the athlete needs to be diligent with completing ROM, quad activation and putting measures around swelling management 4-5 times a day. 

Causes of a lack of knee extension:

Most likely from:

  • Swelling and lack of active control of the distal quads. And they often feed into each other. 
  • Overactive hamstrings muscles to try to support the knee during walking.  

Less likely from:

  • Cyclops lesions, graft placement/ thickness in the intracondylar notch, graft tightness.

Why is this so important?

Swelling, passive knee extension and regaining terminal knee extension with a good distal quads contraction is important as this helps:

  • The patient walk normally without the knee giving way
  • Helps with minimising quad wasting
  • Improves swelling 
  • Reduce the likelihood of developing anterior knee pain. 
  • Helps progress other streams of rehab:
    • Calf raise progressions – having a nice extended knee – leads into our toe off progression of rehab. 
    • Reactive strength stream. Strong terminal knee extension helps to develop foot/ankle stiffness and reactive strength ie toe taps, POGOS, Alt Leg POGOS, SL POGOS. 
    • Need to have 0 deg of knee extension to commence running.

How do we address it?

People often chase knee flexion over knee extension and while knee flexion is important it is often gained much more easily than extension. 

  • Active assisted ROM work with a seatbelt or strap. 
  • Educating the athlete on what position they rest in at home and sleep in. ie rest with a towel under their lower leg and avoid supporting the knee with pillows underneath it. 
  • Isolated Quad Contractions – be individualised. It’s essential to find what works for your patient here:
    • Rolled up towel / small roller under knee. Active assisted Knee extension Holds.
      • Use compex to initially to activate their quads and then use the EMG
      • Active assisted knee extension over a towel/roller reduces the hamstring co-contraction that can occur with straight leg quads activation which can occur if the athlete compensates by digging their heels into the bed.
    • Terminal knee extension in standing with a band behind their knee 
      • Can be used if the athlete is struggling in supine.
      • Compex and EMG can be used in this position to ensure good quads activation. EMG may also be used on the hamstrings to provide feedback to the athlete and reduce activation.

Deficit 2 + 3: Reactive strength/explosiveness:

Reactive strength and explosiveness of the lower limb are often both reduced in athletes post ACLR, with compensatory strategies that we need to be aware of.

Why is this so important?

  • Sports performance – everyone wants to be fast and have a great side step, accelerate fast, sprint etc. 
  • Explosiveness and reactive strength both decrease post ACLR as a result from injury, surgery, pain inhibition, period of immobilisation and swelling
  • Explosive/Reactive actions such as landing from a jump and the deceleration phase of a cutting action are where deficits lie, not only causing reduced sports performance but non-contact ACL injuries. These actions need to be measured and rehabilitated to negate recurrence of ACL injury, thereby improving the sports performance of these actions. 

How do we address it?

A common mistake in ACL rehabilitation is pushing athletes too hard when their knee isn’t ready. An athlete must earn the right to commence reactive strength and explosive training through set objective criteria. This helps clinicians make decisions on whether athletes are ready to commence the training rather than guessing. 

  • Criteria to commence Reactive Strength:
    •  ‘Quiet’ knee -  minimal swelling and pain. 
    • Full terminal knee extension
    • Enough single leg calf strength to hold their weight.
    • Full plantarflexion AROM
  • Criteria to commence Explosiveness Training:
    • ‘Quiet’ knee -  minimal swelling and pain. 
    • Full terminal knee extension
    • Adequate quad strength – athlete able to SL Squat to a minimum of 90deg / isokinetic quads at 200% BW before the athlete leaves the ground. 

How to Measure Explosiveness and Reactive Strength

Testing is essential to provide the athlete with assurance that they are safe to return to play or progress through the planned phases of rehab.

It is best to have a testing battery that is demanding and exposes the athlete to a ‘worse case’ scenario.  Research has shown there are shortfalls in testing only one component such as jump heights and lengths only (concentric measures). Athletes may have persisting biomechanical deficits in their affected limb despite regaining limb symmetry in jumping or change of direction testing times.

Explosiveness Tests include: Counter Movement Jump, SL Vertical Jump, SL Hop for Distance

Reactive Strength Tests Include: DL and SL Drop Jump

Jump performance in ACL Rehab is best measured looking at eccentric, concentric and biomechanical measures.

Concentric deficits in the triple extension phase of jumping will reduce the ability of the athlete to be explosive. If the athlete has struggled to regain terminal knee extension in the initial phase of rehabilitation it will be exposed here.

The eccentric component of jump testing is important as this is where non-contact ACL injuries occur. Eccentric impulse and duration and landing forces should be assessed however landing biomechanics are also essential to address. Common deficits seen post ACLR are landing on a knee that doesn’t want to flex and absorb load with associated compensatory hip and trunk flexion and ankle plantarflexion, increasing the knee extension moment.

What if I don’t have elite equipment?

If you are woking outside the elite space or lack access to biomechanical analysis a jump mat or app that measures performance metrics can be used. Jump Height is superior to hop distance to evaluate the knee and SL drop jump performance metrics such as jump height and RSI should be used as a clinical option for RTS decision making. 

Metrics to aim for prior to return to sport for athletes:

  • CMJ 
    • 39cm Upper range
    • LSI <10% Diff in Ecc, Con impulse  
    • <15% peak landing forces
  • SL Drop Jump
    • <10% Diff in Ecc, Con impulse and peak landing forces
    • Height 21cm is upper range
    • Contact Time 0.28
    • RSI >0.5cm
    • <10% for knee ext moments *biomech analysis
    • <10% for knee ext moments / knee valgus moments *biomech analysis

How do we progressive this stage of rehab?

Common deficits seen in periodic testing should be addressed early rather than allowing it to become a problem later in rehab. Reactive rehabilitation exercises can be commenced early in rehab to address timing and co-ordination. Options for progression through rehab include:

Reactive Strength Rehab Stream:

  1. Toe Taps 
  2. Band assisted 
  3. POGOS 
  4. Alt Leg POGOS 
  5. SL POGOS 
  1. Progressions Fwd/Back 
    1. Line Hopping 
    2. Cone Hopping 
    3. Cone Hopping 2 Forward 1 Back 
  2. High End
    1. Tuck jumps
    2. SL Tuck Jumps 
    3. Drop Jumps 
    4. Drop Hops 

Explosiveness Stream

Start with Eccentric exercises

  • Drop Catches – DL/SL – often these are not overloaded enough 
  • Challenge deeper depths.

Progress to Concentric exercises

  • Non Counter Movement Jumps
  • Jump/SL Jump from Bench/Box

Progress to Combination Jumps to target both eccentric + concentric impulses

  • CMJ / SL CMJ
  • Overload these with a  TrapBar or  Water Bag

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