How Do You Strengthen a Knee?

knee-anatomyYour Knees:  Be Nice to Them, or Pay a Price Later…

Of all the joints in your body, your knees take the most beating.  That is why they are designed as they are:  very thick and broad to support shock and much more than the weight of your body (such as when running).  They are “heavy duty” joints, compared to your finger joints and shoulder joints.

The upper part of the knee joint surface is the distal femur(upper leg); the lower part is the proximal tibia (lower leg).  The distal femur is made up of two, parallel rounded ends called condyles.  They rest on top of the meniscus— the cartilaginous pad covering the proximal tibia that guides the condyles as they glide with knee bending and extension.

The main ligaments that hold the knee together are:

InternallyAnterior cruciate ligament (ACL) and Posterior cruciate ligament (PCL).  They are called “cruciate” because they cross and form an “X” to limit forward and backward movement of the femur relative to the tibia; i.e. stabilize the knee in that plane.

ExternallyMedical collateral ligament (MCL) and Lateral collateral ligament (LCL).  Medial means “inner”, so the MCL connects the femur and tibia on the inner side of your knee; Lateral means “outer”, so the LCL connects the femur and tibia on the outer side of your knee.

Since you can’t control and contract ligaments voluntarily (they are not like muscles), how do you strengthen your knees?

The answer:  strengthen the muscles that MOVE the knee.  After all, a joint like the knee is not just two bone surfaces that contact each other– it includes the muscles that move the joint (by the way, tendons are the ends of the muscles that connect it to bone; they can be long like the patellar and achilles tendons, or they can be short and wide like the gluteus maximus tendon).

The primary movers of your knee are the quadriceps muscle (your thigh muscle) and your hamstrings.    The quadriceps originates from the front of your pelvis (ilium – the pointy bone on either side of your pelvis), travels down and in front of your femur bone; transitions into the superior patellar ligament; connects to the patella (knee cap), and then reforms into the inferior ligament where it attaches to the proximal tibia.

The hamstrings originate from the back of your pelvis (ischial tuberosities– the “seat bones”), run down and behind your femur bone, divide just above the back of the knee passing the sides of the knee, and connect to the proximal tibia from the back.

When the quadriceps shortens with a concentric contraction, it extends (straightens out) the knee.  When the hamstrings shorten, it flexes (bends) the knee.

Here are the Knee Strengthening Exercises:

1.  For the Quadriceps:  sit in a chair, knees bent, feet touching the floor.  Make sure your sacrum is up against the back support of the chair and your are sitting with your torso erect (good posture).  Next, raise your right foot off the floor and extend your knee so that your leg is straight out in front of you, parallel to the floor.   Hold this position for as long as you can.  You’ll notice that your thigh muscle will tighten (isometric contraction), which is what you want.  Switch legs; do about 4-6 repetitions per leg a few times a day.  You can increase the intensity of the exercise by wearing ankle weights (2-5 pounds).

You’ll probably notice that one quadriceps muscle is weaker than the other (you struggle more holding that leg straight, and can’t hold it up as long as the other).  Focus your strengthening on that particular leg.

2.  For the Hamstrings:  Put on ankle weights.  Lie down on your stomach (can be on your bed or carpet) in a comfortable position, body straight, legs together.  Lift the right leg slowly, past 90 degrees, then ease it back down even slower.  Do about 10-20 reps; switch legs.  You can also choose to alternate legs each repetition.

As we get older (especially for men) we lose muscle mass (muscle atrophy) and gain fat cells.  Studies show that the quadriceps muscle is especially affected.  If you are over 40, compare the thickness of your quadriceps muscles to what they were like in your 20s.  This is a big reason why professional athletes gradually lose their agility and performance (their legs “go”), leading them to retire and let the young guys/ gals take over.  It’s also another reason why we are more prone to tripping/falling as we get older.

So, strengthen those knees!  Strong, stabilized knees may save you from knee replacement surgery in your later years.  And this means strong and responsive (to changing loads) quadriceps muscles.

Stay tuned for more exercises that will benefit your knees, hips and entire musculoskeletal system.




Posted in Movement.