Plantar fasciitis is the inflammation of the plantar fascia, a thick band of tissue running across the bottom of the foot. This tissue connects the heel bone to the toes and supports the foot’s arch. Although the pain is localized in the heel and arch, the body’s interconnected structure means foot problems can affect joints higher up. This connection explains how heel pain can contribute to discomfort in the knee.
The Direct Link: How Foot Pain Alters Movement
The human body operates as a continuous mechanical structure known as the lower extremity kinetic chain, linking the foot, ankle, knee, and hip. When plantar fasciitis causes sharp pain upon weight bearing, the body instinctively changes the way it walks to minimize discomfort. This pain avoidance causes an immediate shift in the gait pattern, which disrupts the alignment of the joints above the foot.
The foot absorbs shock and provides a stable platform for movement. When foot function is compromised by pain, it forces the knee and hip to take on mechanical stresses they are not designed to handle. Even small changes in stride length or foot placement translate into increased torque and strain on the knee joint. The resulting knee pain is often a symptom of the foot’s underlying mechanical failure.
Understanding Compensatory Gait and Knee Stress
The altered movement pattern used to avoid foot pain is known as a compensatory gait, and it is the mechanism that loads the knee joint improperly. To shield the painful heel, a person may decrease the intensity of their heel strike or shorten the time the foot spends on the ground. This compensation often leads to excessive pronation (foot rolls inward) or excessive supination (foot remains rigid and rolls outward).
Excessive pronation is particularly problematic because it causes the ankle to roll inward, which subsequently forces the tibia (shin bone) to rotate internally. This internal rotation of the tibia misaligns the entire joint. The kneecap (patella) sits in a groove at the end of the femur, and this tibial rotation changes the angle at which the patella tracks.
The misalignment can lead to a condition called patellofemoral pain syndrome, which is felt as a dull, aching pain behind or around the kneecap. The uneven forces and friction from the poorly tracking patella irritate the joint tissues over time. Furthermore, the compensatory gait causes an uneven distribution of weight, placing increased stress on the ligaments and cartilage within the knee. Individuals with plantar fasciitis have a higher chance of experiencing knee pain, sometimes even in the opposite knee, as the body shifts weight to the less painful side.
Treatment Focus: Resolving Plantar Fasciitis to Relieve Knee Pain
Since the knee pain is frequently a secondary effect of the foot problem, treatment must prioritize resolving the underlying plantar fasciitis and restoring proper biomechanics. A common strategy involves the use of custom or over-the-counter orthotics to support the foot’s arch. Orthotic devices correct excessive pronation or supination, which helps stabilize the ankle and prevent internal rotation of the tibia.
Stretching exercises are important, focusing on the calf muscles and the plantar fascia itself, as tightness in these areas increases tension on the heel. Specific exercises, like performing calf stretches on a step or gently stretching the plantar fascia by pulling the toes back, can help reduce strain on the tissue. Night splints are often prescribed to keep the foot in a slightly dorsiflexed position while sleeping, which maintains a gentle stretch on the fascia and Achilles tendon, helping to reduce the sharp morning pain.
Footwear adjustments are also necessary, requiring supportive shoes that provide adequate arch support and cushioning, while avoiding flat shoes or high heels that can exacerbate the condition. Physical therapy may also include strengthening the intrinsic muscles of the foot and the muscles around the hip and knee to correct imbalances caused by the long-term compensation.