Is It Bad That My Knees Crack When I Squat?
Q: Why do my knees crack when I do squats? And is it bad?
—Will P., Chicago, IL
A: Joints and soft-tissues can make all kinds of noises, from loud popping noises to grating sounds to quiet rubbing sensations. Most of these sounds are categorized by the term crepitus, which essentially means “joint noise.”
Much like when crack your knuckles, loud popping noises from your knees are most likely caused by what is called cavitation. Cavitation results from a change in joint pressure that allows carbon dioxide, which is normally dissolved in your joint fluid—a.k.a. synovial fluid—to come out of the solution and form gas bubbles in the joint. This createa a small cavity in the joint, and when the cavity closes quickly, the bubble essentially “pops” and makes the familiar cracking noise.
In most cases, this is nothing to be concerned about. In fact, the theory that popping your joints will lead to arthritis has absolutely no support in the research literature.
Now some folks will notice a grinding noise in the knee joint when they squat. If it's not painful, it’s categorized as “benign creptius” which, again. is nothing to be concerned about. Many people experience this throughout their lives and never have any problems.
If the condition is painful, then that’s a different story entirely. The undersurface of your kneecap (patella) can rub unevenly on the front of your thigh bone (femur). This causes the cartilage on the undersurface of the kneecap, and on the front of the thigh bone, to soften and eventually wear off so that it hangs in strands of what looks like loose crab meat. This loose cartilage can irritate the surrounding soft-tissues of the knee joint, and result in pain in the front of the knee with squatting, stair climbing, or even just sitting with your knee bent for an extended period of time.
If this is the case, physical therapy, or in worst cases, surgery, will be required to resolve the condition to allow you to return to normal activities.
If you’re still concerned that you may need to do something preventative to protect your knees, there are a few things you can do to assure that you’re keeping your knees healthy as best as you can.
The knee is essentially a “dumb joint” which relies on normal function of the joints above it and below it to assure that it functions normally. Use following tests and exercises to address your knee health needs.
1. Make sure you have normal ankle mobility
Test it: Stand in front of a wall with your right foot pointing toward the wall, about 4 inches from it. (Just put you left foot slightly behind your right.) Keeping your right foot flat, bend your knee and try to touch your knee to the wall. If you can’t touch the wall without your heel coming off the floor, you need to improve your ankle mobility. After you test our right ankle, perform the same test for your left.
The fix: To increase ankle mobility, simply use the test as your exercise. As you try to touch your knee to the wall, hold the stretch position for a five count and repeat it for 20 reps. Perform this 2 to 3 times a day until you can pass the test.
2. Make sure you have normal hip rotation
Test 1: First, test your hip internal rotation. Sit in a chair with your hips and knees bent 90 degrees. Put your two fists side by side between your knees (so that your thumbs are touching each other) and gently squeeze your fists with your knees. Now, keeping your knees against your fists, push your feet apart as far as you can—by raising your lower legs out to the sides—without causing pain. This rotates your hips internally. Your shin should form angle of about 35 to 45 degrees from vertical to indicate that you have normal hip internal rotation.
Test 2: Now test your hip external rotation. Cross your legs “man style” so that your ankle rests on the opposite knee. You should be able to do this comfortably and equally on both legs for normal hip external rotation.
The fixes: If you’re lacking hip rotation in either test, you can use the tests as your fix. Perform the same sequence for both hip rotation tests, hold the test positions for a five count, and repeat for 20 reps. Perform this 2 to 3 times a day until you can pass the tests.
3. Make sure you have normal hip strength and stability
Test it: Perform a single-leg squat by holding one foot off the floor out in front of you. Slowly push you hips back, bend your knee, and sit down to an exercise bench or chair until the thigh of your working leg is parallel to the floor. Then return to standing without using your hands to assist. If you can’t complete the single-leg squat or if your knee collapses inward as you squat, you need to improve your hip strength and stability.
The fix: The single-leg squat. Start with shallow single-leg squats that you can control without difficulty, and while keeping your kneecap in line with the middle of your foot. Progressively try to increase your squat depth until you’re able to reach the parallel position over a series of workouts. Perform 1 to 3 sets of 8 to 12 reps as part of your warmup before your regular workout.
4. Work to maintain normal trunk strength-endurance
Test 1: The static back extension. Simply anchor your legs into a Roman chair or back extension station, then position your body so that your body is in a straight line from head to toe. (See photo. However, you can just cross your arms over your chest, and ideally, find a station that allows you to anchor your feet high enough so that your body is parallel to the floor.) You should be able to hold this position for a full two minutes for normal back extension strength-endurance.
The fix: If you can’t hold for two minutes, do 1 to 3 sets of 6 to 8 reps of the back extension with a 5 to 10 second hold at the top. When this becomes easy, hold a weight plate to your chest. Retest yourself every 2 to 3 weeks to see if you can hold position longer
Test 2: The side plank. Lie on one side with your legs straight, and prop up your upper body on your forearm as shown. Raise your hips so your body forms a straight line from ankles to shoulders, and hold. You should be able to hold this position for 90 seconds on each side.
The fix: If you can’t hold for 90 seconds, perform 1 to 3 sets of 6 to 8 reps with a 5 to 10 second hold at the top. If this becomes easy, raise your top leg off the bottom leg and hold it there. Retest yourself every 2 to 3 weeks to see if you can hold position longer.
Test 3: The plank. Assume a pushup position, but with your elbows bent and your weight resting on your forearms. Your body should form a straight line from your head to your ankles. Brace your abs as if you’re about to be punched in the gut. You should be able to hold this position for two minutes.
The fix: If you can’t hold for 2 minutes (your hips shouldn't sag at any time), perform 1 to 3 sets of 6 to 8 reps with a 5 to 10 second hold at the top. If this becomes easy, alternate raising one leg off the floor to complete your reps. Retest yourself every 2 to 3 weeks to see if you can hold position longer.