One of the main components of early ACL reconstruction rehabilitation post-operatively, is the restoration of quads and hamstrings strength. Achieving symmetrical strength on both legs, and reduced imbalances between quads and hamstring strength has been associated with reduced risk of reinjury. 

Much of the literature suggests there are significant strength deficits for most patients at 6 and 9 months post op, with some research suggesting a 2 year period of rehabilitation is required for both strength deficits and graft healing time frames. These figures can be skewed however by trials that include strength/rehab protocols that are highly variable,  ineffective or simply inadequate. Often the strength training intensity and volume is too low to increase muscle strength and muscle volume, being resistance band exercises and body weight exercises at home, or effective dosages/frequencies in the gym environment.

So how long does it actually take to get strength back following a targeted strength and conditioning program with proper dosages, intensity and frequency?

A small, but interesting study by Welling et al (2019) implemented a progressive strength and conditioning program with 38 male amateur soccer players who had undergone ACL reconstruction, and compared their strength gains not only to their opposite limb but to 30 healthy aged matched controls. 


The program:

Phase 1: Starting 2 weeks post op

  • Range of motion exercises
  • Quads activation exercises

Phase 2:

  • Muscular endurance focus at 2 sets of 15-25 reps, Intensity <50% of 1 repetition maximum (1RM), 2-3 min rest in between sets
  • Exercises such as step ups, leg raises, leg press
  • Provided there was no increase in joint effusion or pain, or pain was below 3/10 within the 24 hours after exercise, exercise were added or the intensity increased
  • Duration generally 10-14 weeks

Phase 3:

  • Progression to strength and hypertrophy dosages of 2-4 sets of 8-10 repetitions, 60-80% of 1RM, 2-3 min rest periods
  • Leg extensions, leg curls, squats, deadlifts, split squats, step-ups, good mornings
  • Alternatives included back squats, front squats, sumo squats, and single leg squats/rises, nordic hamstring curls
  • Duration generally 12-14 weeks

Phase 4:

  • Exercises progressed for maximal strength and muscle hypertrophy with 5 sets of 3 reps at >80% 1RM
  • Duration generally 14-16 weeks


The results:

  • The rehabbed soccer players had no significant differences in quads and hamstring strength in the injured leg compared to the healthy players when tested at 7 months
  • At 10 months, 65.8% of players had comparable quads strength compared to their own non-injured limb, the remaining 36.2% testing below 90% in comparison (so both limbs benefit from the strength program but the non-injured limb gets a head start). 


What does this mean? 

This suggests a well constructed strength and conditioning program can return post ACL reconstructed individuals to a level of strength comparable to the non-injured population within 7 months. Asymmetries between limbs may still be a concern, and reaching a comparable level of strength may be inadequate to prevent a recurrent injury. Perhaps the goal should be to exceed the levels of strength of a non-injured population to mitigate any predisposition to injury.



Welling, W., Benjaminse, A., Lemmink, K., Dingenen, B, Gokeler, A (2019). Progressive strength training restores quadriceps and hamstring muscle strength within 7 months after ACL reconstruction in amateur male soccer players . Physical Therapy in Sport 40: 10-18,



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