In researching proper knee position during the forward lunge (or any lunge for that matter) and squat, I am finding inconclusive evidence as to proper knee position at the end of the eccentric phase. In understanding excessive load on the patella tendon, quadriceps tendon, cartilage and meniscus when the knee moves too far forward, do you know of any research that states the most efficient and safest position of the knee during the lunge and squat?
There is no conclusive evidence on how far the knee should extend over the toes during a squat or lunge. We, at NASM, are tackling the question from a mechanical standpoint. Our position on the question of knee alignment is that based on normal movement patterns, studied from literature as well as assessments within our clinic, a person should not need to extend their knees over their toes when squatting or lunging if they have proper range of motion at each joint. In movement as well as static posture, an individual should align their knee forward, within the line of gravity and not allow forward movement much past the toes.
The passive range of knee flexion is from 130 degrees to 140 degrees. However, knee position is also dictated by ankle dorsiflexion and hip flexion. For example, the knee can flex to 160 degrees when accompanied by hip flexion and bodyweight as your resistance. This is a normal movement and is not detrimental to a healthy knee joint as long as there is limited external load. When squatting or lunging, if a client is extending their knees over their toes, the client is lacking proper extensibility another place in the kinetic chain, possibly the hip or ankle complex if not both. Lack of extensibility yields relative flexibility. This means that in order to complete a squatting movement a person has to compensate by shifting from a predominantly sagittal plane motion at each joint into another plane of motion. An example of this can be seen in pronation-distortion syndrome. Starting from the ankle complex, if the ankle has limited dorsiflexion (sagittal plane motion) due to tight gastrocnemius/soleus muscles, the arthrokinematics are altered. The ankle joint is forced to move into the frontal and transverse planes to allow further movement.
When considering the kinetic chain, if one segment of the chain is altered, compensation must occur all the way up the chain. Limiting the motion at the talocrural joint (ankle), limits movement at the patellofemoral joint (knee). This, in turn, increases femoral internal rotation and adduction. This compensation pattern can force a person to move further into the sagittal, frontal and transverse planes beyond the toes. Some individuals will raise their heels to allow further descent into a squat or lunge because their gastroc/soleus complex is too tight. Another reason that individuals may shift their weight forward in a squat is if they are compensating at the hip by increasing hip flexion instead of knee flexion. This can also occur if the individual was never taught the proper motor patterns for squatting or lunging.
Each of these compensation patterns can shift the body’s center of gravity forward past the axis of rotation placing more strain on the patella tendon and increasing the tension on the quadriceps tendon. When the compensation patterns are addressed with proper flexibility, and an individual is taught neuromuscular control, the knees should never need to move beyond the toes in a squat or a lunge.
To learn more about proper range of motion for each joint, refer to our manual, A Scientific Approach to Understanding Kinetic Chain Dysfunction by Mike Clark.