Common Causes of Knee Pain While Doing Squats and Lunges
Matt Paterson (B.Ex Sci & Sports Science)
Most of us have been there at one time or another—doing our regular exercise routine but now our knees hurt. Knee pain is a common problem for all active people, especially as we get older, and squats and lunges put a lot of pressure on the joint.
Rather than avoid those exercises, let’s take a look at what might be causing that pain. Knowing the cause may lead to treatment or adjustment, and maybe relief.
Know Your Knees
The first step to understanding knee pain is to understand your knees.
Knees are made up of bones, ligaments, tendons, cartilage, and bursae all working together to keep this complex joint operating efficiently.  It’s not at all as simple as the shin bone connecting to the thigh bone.
In addition to a lot of moving parts, the knee is different from other joints in the amount of wear it accumulates through regular activity. Simply walking or standing puts pressure on the joint, pressure that over time can become painful.
Squats and Lunges
Squats and lunges are low impact options to strengthen the legs and lower core. They don’t put as much stress on the body as high-intensity exercises, like running or step aerobics, and are very effective.
Proper squats are done with feet hip-distance apart, chest up, and heels grounded. As you bend at the knee as though you’re sitting in a chair, your knees should never be further forward than your toes. Take it slow, maintain control.
Proper lunges start with feet hip-distance apart, core tight, head up, and upper body straight. Step forward and lower down until you achieve a 90-degree angle with both legs if possible. You can return to your original position or push up and bring the back leg forward for a walking lunge. Do not let your front knee travel past your front toe. 
Causes of Knee Pain While Doing Squats and Lunges
Though it seems counterintuitive, the very squats and lunges that are hurting your knees can also strengthen them and decrease pain. So it’s important to figure out what’s causing those knees to hurt.
Perhaps the most common reason for knee pain during squats and lunges is bad form. When you do a squat, be sure to keep your knees pointed forward (not buckling in or out), your chest up, and push your hips back. Do not allow your knees to move forward—they should stay in line with your ankles. 
Lunges are much the same, no matter how you execute your lunge, make sure your body is straight, your spine is neutral, and your knee does not extend past your toes. Both squats and lunges should be done in front of a mirror occasionally to check your form. 
If you’ve injured your knee in some way—a fall, a twist, even something that seems insignificant at the time—your knee can swell and be painful. Be careful to allow minor injuries to heal before resuming exercise that places stress on the joint. 
Tendon or cartilage tears and knee sprains are serious injuries that cause knee pain. They are likely to need some form of rehab before exercise can resume.\
Arthritis gets more common as we age, but it can appear in younger people as well. With arthritis, the knee suffers from diminished cartilage, the tissue that provides padding within the joint. Because knees get such substantial wear, they are a common place for arthritis to appear; more cartilage disappears the harder the joint is used.
Pain begins when the cartilage gets thin enough that it can no longer absorb the pressure on the joint and the bones in the knee begin to rub. Someone with arthritis in their knees might see swelling and in addition to pain experience stiffness in the joint. 
Patellar tendonitis is an injury resulting from repetitive stress on the joint. Athletes are particularly prone to this injury, especially those who do a lot of jumping.
Patellar tendonitis occurs when the tendon that connects your kneecap to your shin bone becomes inflamed and irritated. The irritation results from small tears in the tendon, which in turn leads to inflammation.
Other factors that increase the risk of this common injury are improper form and inadequate or worn equipment.
Pain from patellar tendonitis is usually located on the kneecap and may show itself as a burning pain when you rise from a squat.
IT Band Syndrome
You may have heard of the IT band—or not. It is the iliotibial band, and it is connective tissue that runs from your outer hip to your knee. IT band syndrome is an injury to that tissue, another one that results from repetitive stress or overuse. Improper form and equipment can also play a role.
When the IT band becomes irritated and inflamed it can cause pain on the lateral portion of the knee. Cyclists and runners are more prone to this injury, and it can cause knee pain during both squats and lunges.
This injury is common in young people, particularly athletes. Also called chondromalacia patella, this condition is a lot of big words that mean irritated cartilage. In this case, the cartilage is under the kneecap and the pain presents around the kneecap.
The moral of the story about squats, lunges, and knee pain is to exercise correctly and listen to our bodies. Proper form can prevent or eliminate knee pain. Done well, squats and lunges are good exercises for strengthening your entire leg, including your knees.
We also need to listen when our bodies tell us we’re working too hard or doing the same movement too often. Knee pain is a signal we should not ignore—these hardworking joints deserve diligent care.