A knee injury can result in pain felt in the hip, a phenomenon frequently observed in clinical practice. The lower extremity functions as a continuous, interconnected mechanical and neurological system. Pain can transfer from the knee to the hip through structural imbalances, changes in the way a person moves, or shared nerve pathways. Understanding these connections is the first step in addressing pain that seems to have migrated up the leg.
The Biomechanical Chain
The hip, knee, and ankle are linked together in the kinetic chain, meaning dysfunction in one joint directly influences the others. The knee joint, situated between the femur and the tibia, is designed primarily for flexion and extension, but it relies heavily on the hip for rotational and lateral stability. When an injury or instability occurs at the knee, the alignment of the entire leg is disrupted. This disruption forces the body’s center of gravity to shift, placing abnormal stresses on the hip joint and surrounding pelvis. A compromised knee may cause the femur to rotate internally or externally to avoid pain, altering the position of the hip socket. This chronic misalignment can lead to improper loading of the hip cartilage and irritation of the joint capsule, setting the stage for mechanical hip pain.
Altered Gait and Muscle Compensation
The most common way knee pain causes hip pain is through the body’s unconscious attempt to avoid discomfort, known as an altered gait or limp. When the knee is painful or unstable, an individual naturally spends less time bearing weight on the injured leg, shortening the stance phase of their stride. This protective movement pattern is often referred to as an antalgic gait. To maintain balance and propel the body forward while favoring the knee, the muscles around the hip have to work harder and in abnormal ways. The gluteal muscles, particularly the gluteus medius and minimus, are stabilizers of the pelvis during walking. These muscles become strained, overworked, and fatigued as they compensate for the reduced function of the injured knee. This chronic overuse can lead to inflammation and pain in the hip’s soft tissues, resulting in conditions like greater trochanteric pain syndrome.
Referred Pain and Nerve Pathways
Beyond mechanical compensation, pain can also be transferred from the knee to the hip through a neurological mechanism called referred pain. Referred pain occurs when the brain misinterprets the source of a pain signal because the nerves supplying two different areas share the same spinal cord segment. The hip and knee are innervated by nerves that originate from the lumbar spine, specifically the femoral and obturator nerves. Irritation or inflammation localized at the knee, perhaps from a meniscal tear or arthritis, sends a signal through the sensory nerves to the spinal cord. Because the brain receives input from the same set of nerves that supply the hip region, it may incorrectly perceive the pain as originating from the hip joint itself. A person can feel a deep ache in their hip even when the hip joint is structurally healthy, and the true source of irritation is located entirely in the knee.
When to Seek Professional Help
Any new or persistent pain in the hip following a knee injury warrants professional evaluation, particularly if the pain lasts longer than a few weeks despite rest. Warning signs that require prompt medical attention include a rapid worsening of pain, an inability to bear any weight on the leg, or symptoms accompanied by a fever. These signs can indicate a more significant injury or an infection within the joint.
A medical professional can perform a comprehensive assessment to distinguish between mechanical pain from muscle compensation and referred pain from nerve involvement. A proper diagnosis is necessary to create an effective treatment plan, which may involve physical therapy to address the biomechanical chain and muscle imbalances. Ignoring persistent dual pain can lead to chronic movement patterns that complicate recovery and potentially cause long-term joint wear.