Knee gait

THE KNEE AND GAIT

During the normal gait cycle, the knee goes through a range of 60_ (0_ extension at initial contact or heel strike to 60_ at the end of initial swing). There is some medial rotation of the femur as the knee extends at initial contact and just prior to heel-off.

Muscle Control of the Knee During Gait

Stability during the gait cycle is efficiently controlled by the normal function of the muscles that attach at the knee.

Knee gaint

Quadriceps

 The quadriceps muscle controls the amount of knee flexion during initial contact (loading response) and then extends the knee toward mid-stance. It again controls the amount of flexion during pre-swing (heel-off to toe-off) and prevents excessive heel rise during initial swing. With loss of quadriceps function, the patient lurches the trunk anteriorly during initial contact to move the center of gravity anterior to the knee so it is stable or rotates the extremity outward to lock the knee.228 With fast walking, there may be excessive heel rise during initial swing.

Hamstrings

The hamstring muscles primarily control the forward swing of the leg during terminal swing. Loss of function may result in the knee snapping into extension during this period. The hamstrings also provide posterior support to the knee capsule when the knee is extended during stance. Loss of function results in progressive genu recurvatum.

Soleus

 The unijoint ankle plantarflexor muscles (primarily the soleus) help control the amount of knee flexion during pre-swing by controlling the forward movement of the tibia. Loss of function results in hyperextension of the knee during pre-swing (also loss of heel rise at the ankle and thus a lag or slight dropping of the pelvis on that side during the pre-swing phase).

Gastrocnemius

 The gastrocnemius muscle provides tension posterior to the knee when it is in extension (end of loading response or foot flat and just prior to pre-swing or heel-off). Loss of function results in hyperextension of the knee during these periods as well as loss of plantarflexion during pre-swing or push-off.

Hip and Ankle Impairments

Because the knee is the intermediate joint between the hip and foot, problems in these two areas can interfere with knee function during gait. Examples:

Hip flexion contractures

 Inability to extend the hip prevents the knee from extending just before terminal stance (heel-off).

Length/strength imbalances

 Most of the muscles functioning to control the hip are two-joint muscles that also cross the knee. With asymmetry of length and strength, unbalanced forces may stress various structures in the knee, giving rise to pain during walking or running. muscle increases stress on the IT band, which could lead to lateral knee pain; or it could affect tracking of the patella and lead to anterior knee pain. Overuse of the hamstring muscle group increases posterior translation forces on the tibia, requiring compensation in the quadriceps femoris muscle and resulting in anterior knee pain .

Foot impairments

 The position and function of the foot and ankle affect the stresses transmitted to the knee. For example, with pes planus or pes valgus, there is medial rotation of the tibia and an increased bowstring effect on the patella, increasing the lateral tracking forces.

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