Knee pain is extremely prevalent and increases drastically with age affecting one’s quality of life and ability to engage in a program of regular exercise (Kim, et al., 2011). In fact, the number of total knee replacement surgeries has more than doubled in the last 10 years (Weisnstein, et al., 2013). So, what is causing this epidemic and what can you do as a fitness professional to ensure both you and your client’s knees remain pain-free and don’t affect your workouts and active lifestyle?
- The reader will learn about a common cause of knee pain
- The reader will learn about what muscles/movements contribute to knee pain
- The reader will learn what they can do to address the underlying causes of knee pain
To understand what causes knee pain, you must first learn some basic concepts in biomechanics to appreciate how the knee should function when things are working correctly. Movements of the knee link the motions of those structures above and below it (i.e., thigh/hip above and foot/ankle/shins below) so that the entire lower kinetic chain can function in a coordinated manner. For example, during weight-bearing activities (e.g., squatting) the foot and ankle roll inward (i.e., pronate) and flex (i.e., dorsiflex) as the thigh/hip also rolls inward (i.e., internally rotates) and flexes. To synchronize these movements between the lower and upper leg, the knee must also rotate inward and flex (Kendall, McCreary & Provance, 2005).
A Common Cause of Knee Pain
Although the knee does have some capability to rotate, the knee joint itself is designed primarily to bend and can actively flex to 135°. In contrast, the tibia (i.e., shin bone) can rotate between 20 to 30° (in relation to the femur) and the thigh/hip has the capacity to rotate inward about 30° (Petty & Moore, 2002; Magee, 2014). Therefore, while the knee is well-equipped to bend, its ability to rotate inward during weight-bearing movements is limited.
The rotational movement capabilities of the upper and lower leg are very important for maintaining knee health because when both the upper leg (i.e., thigh/hip) and lower leg (i.e., shins) are rotating well together (and in the same direction) there is very little rotational torque experienced by the knee. However, if rotational movement is restricted in the upper or lower leg, stress is transferred to the knee joint instead and pain can result.
To help you understand this concept more completely, consider the following example. If you turn your head to the right to look over your right shoulder, your neck has to rotate substantially. However, if you also turn your torso and shoulders to the right as you turn your head, then your neck does not rotate very much at all (in relation to your head/torso/shoulders) and experiences very little rotational torque as a result. This is why it is so important for both the lower leg and upper leg to rotate well together. These coordinated movements decrease stress to the knee and ensure it stays pain-free during weight-bearing activities.
Muscles and Their Role in Knee Pain
Understanding the role of muscles in facilitating movement of both the upper and lower leg will help you identify what soft tissue structures are contributing to a person’s knee pain and enable you to design appropriate corrective exercise strategies to alleviate it. The tibialis anterior, tibialis posterior and peroneals, for example, are all large muscles in the lower leg that wrap under and around the ankle terminating on the underside of the foot (Gray, 1995). During weight-bearing activities, these muscles lengthen under tension (like a rubber band) to control pronation of the foot and internal rotation of the ankle/lower leg. However, if these muscles are restricted or unable to lengthen effectively, then the lower leg cannot internally rotate well potentially causing stress to the knee (Price & Bratcher, 2010).
Internal rotation of the upper leg is controlled, in part, by the lengthening of the hip flexors, glutes, adductors and deep hip rotators (Price & Bratcher, 2010). If any of these structures are unable to lengthen effectively during weight-bearing movements (perhaps due to orthopedic issues, sedentary environments and/or musculoskeletal imbalances), these muscles can become weak and ineffective at facilitating internal rotation of the thigh/hip. Consequently, the knee joint bears the brunt of the movement stress as it tries to rotate inward without the bones above it cooperating.
It is particularly important to note that a weak or deconditioned gluteus maximus can contribute significantly to knee pain because it has attachments on both the upper and lower leg. Lengthening of this muscle helps control (and slow down) internal rotation of both the lower and upper leg. Therefore, the health and function of the gluteus maximus is extremely important to alleviating/addressing knee pain and should be prioritized as part of any corrective exercise program designed to address this problem.
Corrective Exercise Strategies and Assessments
To strengthen the muscles that assist with internal rotation of the upper and lower leg, all of the bony structures and joints that these soft tissues either originate from, attach to, or cross over must first be working correctly. For example, optimal functioning of the hip-flexors, glutes, adductors and hip rotators is contingent on mobility of the lumbar spine and pelvis since all these muscles originate from those areas of the body. Similarly, mobility of the foot and ankle complex is essential due to the origin and insertion points of the muscles that control rotation of the lower leg on these areas. Therefore, corrective techniques designed to restore joint mobility must be utilized before strengthening exercises are introduced.
Begin your corrective exercise program by applying strategic self-myofascial release and gentle stretching exercises that target the muscles (and other soft tissues) that help facilitate movement in the hip/pelvis/lower torso and foot/ankle areas of the body (e.g., gluteus medius, gluteus minimus, tensor fascia latae, IT band, gluteus maximus, hip-flexors, quadratus lumborum, erector spinae, hip rotators, internal and external obliques, rectus abdominis, adductors, rectus femoris, hamstrings, tibialis anterior, tibialis posterior, peroneals and intrinsic muscles of the feet) (Price & Bratcher, 2010).
Once mobility of both the upper and lower leg have been improved with self-myofascial and stretching techniques, evaluate the ability of these structures to rotate by performing the following assessments.
Assessment 1: Evaluate Lower Leg Rotation
Instruct your client to stand on top of a BOSU in a split stance with their hands on a wall or counter for support. Coach them to push their back heel down (i.e., dorsiflex the ankle) and rotate their ankle and lower leg inward (i.e., toward the midline of the body). Tell them not to move their hips/pelvis as they try to rotate their ankle and lower leg. Teach them to perform the movement first with their back leg straight and then with it slightly bent. Evaluate their ability to rotate their lower leg/ankle on both sides. If you do not notice a difference, ask your client which side (or both) they have difficulty rotating.
Assessment 2: Evaluate Upper Leg Rotation
Instruct your client to lie on the floor on a mat. Ask them to spread their legs about 18 inches to 2 feet apart and try to turn both of their legs inward so their feet move toward each other. Evaluate to see if one leg cannot turn as far in as the other leg. If you do not see a visible problem, ask your client to tell you if they feel a difference between the sides and/or if one side feels more difficult for them to turn in. Both legs should be able to turn in about 30°. In the example image below, the client has almost an acceptable range of motion for her left leg, while her right leg is severely lacking the mobility to rotate inward.
If a client is unable to rotate either their upper or lower leg effectively, revisit the self-myofascial release and stretching exercises until the desired rotational movement(s) can be achieved.
Introducing Strengthening Exercises
Once your client is able to internally rotate both the upper and lower leg correctly, you can progress your corrective exercise program by introducing integrated strengthening movements that challenge the lower kinetic chain under load. It is important that you acquaint your client with strengthening exercises gradually, however, especially if they are currently experiencing pain. Moreover, if orthopedic issues of the lumbar spine and hips such as disc bulges, disc degeneration, sacroiliac joint inflammation and/or osteoarthritis are suspected, you should refer your client to a licensed medical professional or physical therapist to gain clearance before attempts at strengthening these areas of the body are introduced. Similarly, if your client reports any past injuries or surgeries of their foot/ankle complex, the appropriate consent should be obtained before more dynamic movements (i.e. strengthening exercises) are introduced to their program (Bryant & Green, 2010).
The goal of the strengthening portion of your corrective exercise program is to build strength by performing movements that require internal rotation of both the upper and lower leg together in a coordinated manner. This can be achieved by gradually incorporating weight-bearing, closed chain movements (i.e., where the foot is in contact with the ground/a contact surface) such as squats and lunges. These exercises can be progressed when your client is ready by adding movements of the upper body (like reaching out from the body) that encourage the leg(s) to internally rotate to a greater degree (see figure below).
As you introduce these more challenging movements, it is advised that you offer clients the use of a balance aid such as a chair or dowel rod balanced on end until they can perform such movements with confidence.
The knee joint bears the stress of movement imbalances above and below it. By evaluating and correcting any deficiencies in either/or the ankle/lower leg and the thigh/hip you can decrease the rotational torque experienced by the knee, thus decreasing pain and improving long-term function.
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Weinstein, A. M., Rome, B. N., Reichmann, W. M., Collins, J. E., Burbine, S. A., Thornhill, T. S., Wright, J., Katz, J. N., and Losina, E. (2013). Estimating the burden of total knee replacement in the United States. Journal of Bone and Joint Surgery (American edition). Mar 6;95 (5):385-92.