(EXPECTED BETWEEN WEEKS 1 – 4 OF RECOVERY)
One of the common features of injury is a restriction of movement of the knee and due to bruising and swelling of the surrounding tissues. There is a commonly believed fallacy that strength around a joint trumps all, where in actuality it can create more issues in the long run with instability in the end ranges of motion as movement improves. There’s no point being really strong in a quarter squat when you collapse doing a half squat when you’re healthy. That is why it’s important, especially in the early days post injury to improve the range of motion (gently of course!). The closer you can get to full normal movement with the knee joint , the more successful the following strength training routine is likely to be. This advice is especially pertinent post surgery; anything from debridement to a full knee replacement will cause massive impacts to mobility. The best exercise I can recommend for restoring mobility is the assisted knee slide, either prone or seated. It can also be done in the bath using the hot water to assist in improving range.
The muscles around a healthy knee don’t contract in a linear fashion during movement as evidenced in this study (2). Meaning there will be a stronger contraction during certain parts of the movement, not only is this vital for understanding how the knee works but also how it can go wrong. Training to increase contraction (or in most cases force) such as leg extension machine exclusively can create abnormal a muscle recruitment pattern along the range of motion leading to overtraining syndromes (3).
(EXPECTED BETWEEN WEEKS 4 – 12 OF RECOVERY)
Exploding out of a contracted position may be commonly associated with weightlifters and sprinters but this explosive type of strength should not be confused with the joint strength and stability that pertains to health. Because of the way muscles contract as mentioned earlier it’s important to try to make sure any motion that is restored to the knee joint is as uniform as possible. What does that mean and why is it important? It means that the movement should seek to be as smooth (no shaking) and controlled as possible, the movement of going from the bottom of the movement to halfway should be the same speed as from halfway to the top of the movement. Many people seek to make squat and lunging movements easier by speeding up as they get closer to the the top of the movement, using the momentum of their body and therefore inadvertently reducing the benefit of the exercise. By avoiding balance perturbation, any strength building exercise will be challenging and so it should be in order to improve dynamic stability (4).
In order to get the maximum benefit from an exercise designed to enhance joint stability though movement I encourage the use of movement pacing or tempo. Simply put, in a split squat you would descend for 10 seconds, hold the lower position for 3 seconds and then slowly raise up for 10 seconds. Ensure the upper body remains rigidly upright and does not sway as you try to catch balance.
(EXPECTED BETWEEN WEEKS 4 – 20 OF RECOVERY)
As smooth and controlled your knee movements may be they can still create issues if the the other knee doesn’t move in a similar way. This is why it is important to try to perform exercises on both sides evenly, not only to ensure the quality of the movement is equivocal but to prevent overdevelopment of musculature on one leg. A surprisingly common problem post injury, symmetrical exercises should be started as soon as possible when exercises begin and should take precedence when normal levels of knee function are reached. Tempo squats are my exercise of choice for this; however it is vital that when squatting the body is kept central and there is no shifting of weight from one side to the other during the movement.
(1) Gage, B. E., McIlvain, N. M., Collins, C. L., Fields, S. K. and Dawn Comstock, R. (2012), Epidemiology of 6.6 Million Knee Injuries Presenting to United States Emergency Departments From 1999 Through 2008. Academic Emergency Medicine, 19: 378-385. doi:10.1111/j.1553-2712.2012.01315.x
(2) Lanza MB, Balshaw TG, Folland JP. Explosive strength: effect of knee-joint angle on functional, neural, and intrinsic contractile properties. Eur J Appl Physiol. 2019;119(8):1735–1746. doi:10.1007/s00421-019-04163-0
(3) Patel DR, Villalobos A. Evaluation and management of knee pain in young athletes: overuse injuries of the knee. Transl Pediatr. 2017;6(3):190–198. doi:10.21037/tp.2017.04.05
(4) LEWEK, M. D., T. L. CHMIELEWSKI, M. A. RISBERG, and L. SNYDER-MACKLER. Dynamic knee stability after anterior cruciate ligament rupture. Exerc. Sport Sci. Rev., Vol. 31, No. 4, pp. 195–200, 2003.