As a component of the gait cycle, the stance leg phase is an important component of locomotion. Impairments can significantly reduce quality of life.
What is the stance leg phase?
As a component of the gait cycle, the stance leg phase is an important component of locomotion. A gait cycle is composed of a stance leg phase and a swing leg phase of a leg. It begins and ends when the heel touches the ground. The stance leg phase represents the part where the foot makes contact with the ground and the muscles propel the body. It is divided into 5 sub-phases in gait analysis, with the first and last being very short and each representing the transition from or to the swing leg phase. These moments are also called double loading phases, because then both feet are in contact with the ground at the same time. First, the heel reaches the ground without weight bearing followed by weight bearing with the sole of the foot making contact with the ground. In the middle stance phase, the foot is approximately under the body’s center of gravity and the entire body weight acts on the leg. From this position, the body is transported further forward via an extension in the hip joint to finally initiate the subsequent swing leg phase by lifting the heel. At normal gait speed, the calf muscles do the main work in propelling the body. Synchronous to the forward shift of the body, the rolling motion takes place on the foot.
Function and task
The stance leg phase is an important part of the forward movement and thus the mobility of a person. The propulsion of the whole body takes place in this period, while in the swing leg phase only the free leg is transported forward. Different mechanisms are able to adapt the movement process to different needs and conditions. In normal walking, the phases are timed in such a way that the load on the joints is kept as low as possible in the rollover phase and vertical movements are minimized. The control via the knee joint is primarily responsible for this. In the phase of weight transfer, it is still clearly bent in order to be able to absorb the incoming load well. Full extension is not achieved until the load is completely taken on. An acceleration of the movement sequence leads to the first phase being increasingly skipped. The foot touches down in the middle and immediately with the ground contact the weight transfer takes place. This is also due to the fact that in running there is a flight phase and when one foot lands, the other leg is still completely in the air. Walking is different from this. Faster locomotion also means that the calf muscles no longer do the main work of propulsion alone, but are increasingly supported by the hip extensors. This coupled activity of the two muscle groups is particularly strong when running up a hill, for example. Functional differences appear in the movement sequence depending on whether it is downhill or uphill. When walking uphill, the forefoot rather than the heel is placed on first, whereas when walking downhill, the heel load is emphasized and this phase is prolonged. Weight transfer now occurs before the sole of the foot reaches the ground. For a round and rhythmic gait pattern, the timing of the movements of both legs and the coordinative correct execution are particularly important.
Diseases and complaints
All injuries and diseases in the leg area that cause unsteadiness or are accompanied by pain that increases when stepping have a negative effect on the performance of the stance leg phase. Essentially, the gait rhythm changes when a leg is affected. The pain or the intensification of pain during weight bearing causes the contact time to be kept as short as possible, the leg then leaves the ground again faster than normal. Compared to the unaffected leg, the stance leg phase is shortened and a limping gait pattern develops. Such gait changes can be the result of acute injuries, such as strains, muscle fiber tears, meniscus lesions or fractures, but also of degenerative changes in the hip or knee joint. Osteoarthritis of the hip joint in particular often shows typical gait changes that affect the stance phase.This includes the so-called waddling gait (Duchenne limp), in which affected people tilt their upper body toward the affected leg during the stance phase to reduce the load and avoid the pain. The other gait pattern change in hip osteoarthritis is the so-called Trendelenburg sign. The muscles, weakened by the sparing behavior, can no longer keep the pelvis horizontal in the stance leg phase and it tilts downward in each case. This results in an appearance that resembles an uncoordinated model gait. Neurological disorders can affect the gait pattern as a whole and the stance leg phase in particular. Nerve lesions resulting in paralysis of the muscles responsible for weight bearing can result in insufficient strength being available. Optimal function of the quadriceps femoris muscle is particularly important, since this muscle plays the main role in holding the body up against gravity. If this muscle is completely or incompletely paralyzed, e.g. as a result of a herniated disc, a peripheral nerve lesion or a central neurological disease, the leg cannot be stabilized in the stance phase or can only be stabilized briefly. Similar mechanisms also occur in elderly people who suffer from a general weakness of the musculature. Hemiplegia resulting from a stroke often leads to a spastic gait pattern in which the processes of the stance leg phase are significantly altered. The foot is placed immediately, with a complete knee extension, with the forefoot. The movement pattern is then altered coordinately.
