The knee-strengthening exercise guide you never knew you needed
Knee injuries are notoriously common, painstaking to resolve and often utterly avoidable. The problem isn't weak knees, per se, but poorly conditioned muscles, ligaments and tendons that support the joint, or poorly drilled technique when working out or playing sport.
Fortunately, you can protect and fortify the region by including select knee-strengthening exercises in your warm-ups and workouts, lubricating the joint with mobility drills and minimising bone-shuddering impact with smart exercise substitutions.
Ready for a good old-fashioned knees up? Here's everything you need to know about knee anatomy, knee injuries, knee pain and knee gains.
Why we need strong knees
As a simple pivot joint, the knees serve to flex and extend the knee, allowing us to sit, stand, walk, run, jump and kick. Often in a straight direction. Weak knees will limit our capacity to excel in each of these departments, with pain, injury and profanities the typical consequence.
On the flipside, muscular quads and hamstrings coupled with robust ligaments and tendons, mobile ankles and hips, good general flexibility and a patient, measured training plan will all add up to strong, resilient and injury-free knees.
The issue is, few of us have the time or inclination to ensure all these bases are covered, and as a consequence the knees can bear the brunt of strains and pains incurred playing sports, lifting weights or simply hot-footing it for the bus.
The muscles that support the knees
Several muscles work in harmony to flex and extend the knee joint, enabling the aforementioned sitting, standing, walking, running, etc. They are bracketed into two groups.
Muscles called 'flexors' pull your knee in when straightening the leg. These include the four muscles of the quadriceps (vastus lateralis, intermedius and medialis, plus the rectus femoris) and a small muscle located deep in the anterior compartment of the thigh which acts to stabilise the knee joint.
Rectus femoris
Vastus lateralis
Vastus intermedius
Vastus medialis
Articularis genus
Opposing muscles called 'extensors' work to pull the shin towards the back of the upper legs. These include the three muscles of the hamstrings (biceps femoris, semitendinosus and semimembranosus), one in the medial thigh that aids internal knee rotation (gracilis) and three of the four calf muscles.
Biceps femoris
Semitendinosus
Semimembranosus
Gastrocnemius
Plantaris
Gracilis
Popliteus
Common causes of knee pain
Knee pain can typically be categorised as either chronic or acute, says physiotherapist Mike Aunger, founder of Technique Health & Fitness. 'Chronic pain tends to relate to long-standing issues, such as osteoarthritis, a degenerative condition within the knee joint that's most common among older populations,' he says.
Whereas acute pain is often associated with an injury, such as on the field of a rugby or football pitch, when you twist suddenly and your studs get caught in the turf. Most people who walk – or, rather, limp – through Technique's doors presenting with knee pain relate to meniscus or cruciate ligament injuries.
Yet acute issues can also build up gradually, such as inflammation of the bursa, patellar tendon or quadriceps tendon due to overload from tackling too much too soon in your training plan. Remember: slow and steady wins the race.
According to a 2023 literature review, knee pain accounts for approximately 5% of all primary care visits in adults worldwide, with osteoarthritis affecting an estimated 654 million people globally and one in four likely to experience patellofemoral pain at some point over their lifetime. If you run, squat or kick a ball regularly and are aged under 40, chances are you're not one of the lucky ones.
Common knee injuries
Patellofemoral pain syndrome (runner's knee)
Also known as runner's knee, PFPS is characterised by pain in and around the front of the knee and kneecap (patella). It's commonly caused by overuse, like when you think you can jump from a predominantly sedentary existence into running a marathon overnight, or due to weak or tight thigh muscles that cause misalignment of the kneecap.
Patellar tendinitis (jumper's knee)
This involves injury or aggravation of the patellar tendon, which connects the kneecap to the shinbone. Colloquially known as jumper's knee, it's especially prevalent in sports involving jumping and overloading of the patellar tendon, with one study suggesting it affects over 40% of elite volleyball and basketball players.
Ligament tears
Anterior cruciate ligament (ACL) injuries are common in football and especially disruptive, given they typically require invasive reconstructive surgery and 12+ months on the sidelines. In the US, 80% of ACL injuries occur in five sports: soccer (football), American football, basketball, rugby and lacrosse. The common denominator being abrupt changes in direction.
Imbalances in muscle strength between your quads and hamstrings, genetic predisposition, fatigue and overuse can all increase risk factors. But the most obvious risk factor for ACL injuries by far is being female. Incidence rates of ACL injuries are between 2.4 and 9.7 times higher in female athletes competing in similar activities.
Torn meniscus
The meniscus acts as a shock absorber between the shin and thighbone. This tough, rubbery cartilage structure is prone to tearing when you suddenly twist while bearing weight, such as when landing awkwardly from an aborted slamdunk.
Are squats bad for the knees?
Just like how deadlifts aren't bad for your back, squats aren't bad for your knees. The exercise is neither intentionally malicious, nor sentient, but your technique might be doing you more harm than good. Knees caving in, ankles lifting off the floor, chest collapsing forward… sound familiar?
Aunger, a specialist in knee rehabilitation, agrees. 'Overloading the knee with squats can be suboptimal in some cases, like when recovering from an acute meniscus tear or surgery,' he says. 'But for the vast majority, squats can be an effective way to manage and improve knee pain so long as they are performed safely.'
If you've been given a clean bill of health by your doctor or physio but your form is letting you down, this wall-facing squat challenge from FIIT trainer Gustavo Vaz Tostes should help right any squat technique wrongs.
There are three rules:
Both hands must stay together, touching the wall overhead throughout.
Both feet (or toes) must be in contact with the wall at all times.
You must perform a full squat with hips dropping below knees.
Did you flunk the test? Don't be disheartened. Vaz Tostes suggests moving your feet away from the wall until you can just about complete one rep. Now aim for five sets of three reps, with a 10-15 second pause at the bottom, to drill flawless squat technique that'll spare your knees any discomfort.
Knees over toes — is it safe?
This debate has raged since the dawn of time. Or at least since physical education was first introduced in British schools in the late 1800s. The misconception that has prevailed is that you shouldn't let your knees travel past your toes when performing squats or lunges.
Yet, gradually, it is being dismantled by an army of trainers demonstrating it to be not only safe, but also essential, to strengthen the knee, reduce pain and develop functional mechanics for sports like basketball.
Trainer Ben Patrick, aka Knees Over Toes Guy, is at the forefront of that movement. He suggests the root cause of this knees over toes debate stems from a 1978 Duke University study that determined there is more pressure on your knees when they go over your toes. 'No duh!' he writes on his site, Athletic Truth Group. Patrick argues that the result has been poorly taught mechanics that's leading to a spike in knee surgeries and replacements.
His remedy: add knee-strengthening exercises like backward walks, sled drags and reverse step-ups which all involve allowing the knees to travel beyond the toes.
How to strengthen knee ligaments and tendons
Knee ligaments and tendons should be treated in much the same way as muscles when it comes to strengthening the knee: by gradually and meticulously fortifying them with resistance exercise.
'Loading the knee is almost always the best way to strengthen tissues around the knee,' says Aunger. 'Adaptive changes within the muscle, tendon and ligament will all adapt to increased load over a period of time.'
Including a mix of compound and isolation exercises over a period of time will do the trick, then if they react well you can start layering on more dynamic exercises like plyometrics to develop explosive power.
Physio-approved knee-strengthening exercises
'You don't need to look much further than squats, deadlifts, split squats and the leg press,' argues Aunger, who has practiced as a physiotherapist for over 20 years across elite sport, the military and occupational health.
'These multi-joint exercises provide bonus benefits for the hips, ankles and muscles throughout the lower limb and tend to form the core components in all my long-term rehabilitation plans for most clients.'
Bodyweight exercises like single-leg squats from a bench will also help develop stability throughout the lower leg kinetic chain, while improving proprioception, coordination and balance that will come to your rescue to protect the joint when under a heavy barbell or jinking down the wing.
Aunger says developing core strength around the pelvis and glutes with planks, side planks and Pallof presses will similarly help protect the knee, while training the calves to aid with shock absorption is often an underutilised tool in knee rehabilitation, especially for anyone involved in impact sports like running or team sports.
Top knee-strengthening exercises
Knee rotations
Use this quick hack from Charlotte Hazelwood, aka Elevate With Charlotte to mobilise your knee joint and banish knee pain when running.
Reverse step-ups
Performed either flat on the floor, as demonstrated here by The Pain Free Guy, or on a low step, reverse step-ups work through a reduced range of motion when compared with a squat or lunge to flood the area with blood, warm up the muscles and mobilise the joint.
Heels elevated reverse step-ups
Progress the rejuvenating reverse step-up magic further with your heels elevated. Make sure you support your weight by holding onto the bannister or a PVC pipe as you work through a set of 10 reps each side. Keep it slow and controlled.
Backward walking
Backward walking – or 'retro-walking' as it's known in academic circles – has long been practised by physios to strengthen the knees ever since it was first popularised in ancient China. One 2018 review and meta analysis found moving in reverse improved balance and stability in cases of juvenile rheumatoid arthritis and improves outcomes for patients with knee osteoarthritis, while 'gait parameters and muscle strength in anterior cruciate ligament injury' improved significantly when backward walking was included as an exercise. If you have access to one, a non-motorised treadmill is the easiest way to incorporate backward walking into your workouts.
Sled drag
Adding load to the mechanics of backward walking is a simple way to progress this movement further while sparing the joints from increased stress. In physiotherapy, light sled drags are often used to relieve back pain and treat arthritis because it puts less strain on the joints. Something to bear that in mind next time you're cursing the weighted sled pull station at HYROX.
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