Knee pain is a widespread condition that affects people of all ages. It is often assumed that the cause of the pain is directly in the knee joint. However, medical examinations repeatedly show that the hip plays a central role in the development of knee pain. Pain radiating between the hip and knee joint is not uncommon and can significantly complicate the diagnosis.

In this article, we take a detailed look at the connection between knee pain, hip diseases, and the mechanisms of pain radiation. We illuminate the medical background, treatment options, and preventive measures.

The complex connection between knee and hip

Anatomical Basics

The knee and hip joints are part of the lower extremity and work closely together to ensure the mobility and stability of the human body. Problems in the hip area can lead to biomechanical incorrect loading, which has a negative impact on the knee.

1. Nerve pathways and pain radiation: The nerves that supply the hip overlap with those of the knee. Pain from the hip is therefore often 'projected' and perceived in the knee.
2. Biomechanics: Misalignments or diseases of the hip change the gait pattern and can increase the load on the knee joint, leading to overloading or wear.

Pain Radiation: How Hip Problems Become Noticeable

• Hip joint arthrosis: One of the most common causes of pain radiating into the knee. Typical are load-dependent pains, which are first noticeable in the knee.
• Hip impingement: Restricted mobility of the hip can strain the iliotibial band muscle and secondarily lead to knee pain.
• Damage to the lumbar spine: Often, the pain perception of the spine, hip, and knee overlaps due to the same nerve pathways.

The role of the iliotibial tract in pain referral from the hip to the knee

The iliotibial tract, a broad tendinous plate on the outside of the thigh, plays a central role in the transmission of force and stability of hip and knee joint movements. Through its connection to the hip musculature and the knee, it can be both the cause and the pathway for pain transmission.

Anatomical Connections

The iliotibial tract originates as a thickening of the fascia lata at the iliac crest. It is connected to several important muscle groups:

• Tensor fasciae latae muscle (TFL): A hip flexor that tightens the tract and provides stability during gait.
• Gluteus maximus muscle: Also supports the tension of the iliotibial tract.

At the knee, the tractus attaches to the Gerdy's tubercle (lateral tibial condyle) and stabilizes the joint in extension and flexion.

Mechanisms of pain referral

Pain that radiates from the hip to the knee can be mediated through the iliotibial tract by the following mechanisms:

1. Increased tension in the iliotibial tract:

• Causes such as hip misalignments, arthrosis, or muscular imbalances can overstress the tract.
• A chronic tension transmits friction or tension to its distal attachments at the knee joint, leading to pain in the area of the lateral knee.

1. Inflammation of the iliotibial tract (IT band syndrome):

• Repetitive movements, such as running or climbing stairs, cause friction between the tractus and the lateral femoral condyle (over the lateral epicondyle).
• This is often misinterpreted as an isolated knee problem, but often has a primary cause in hip mechanics.

1. Myofascial pain transmission:

• Trigger points in the musculature, especially of the tensor fasciae latae or gluteus maximus, can radiate along the iliotibial tract along its path to the knee.

Causes and triggers in the hip region

Common triggers of iliotibial tract overload, which cause secondary knee pain, are:

• Hip dysplasia: Causes altered loading patterns of the lateral thigh structures.
• Hip impingement: Limitations in hip mobility lead to compensatory overloading of the tractus.
• Pelvic malalignment: Imbalanced tension in the tract due to asymmetric pelvic position.

Common clinical pictures in the context of hip and knee

Osteoarthritis: When the hip affects the knee

Hip osteoarthritis (coxarthrosis) can lead to gait changes and increased stress on the knee. Increased limping or compensatory postures excessively stress the knee joint and accelerate the wear process.

Hip bursitis

Inflamed bursae ("bursitis") at the hip often cause local pain that can radiate to the knee. The similar symptoms can lead to misdiagnosis.

Herniated discs

A herniated disc in the lumbar spine can exert pressure on the sciatic nerve and trigger pain that radiates to both the hip and knee.

Knee pain typical in hip dysplasia

Hip dysplasia is a congenital or early childhood-acquired malformation of the hip joint, in which the acetabulum inadequately encompasses the femoral head. This faulty fit leads to instability of the hip joint, which can cause various mechanical and neural problems in the long term, including knee pain.

Mechanisms explaining knee pain in hip dysplasia:

1. Biomechanical Effects:

• Due to the unstable hip, the power transmission during walking is disrupted. The load is often shifted to the knee joint, which can lead to incorrect stress and pain in the knee.
• Compensatory changes in the leg axis often occur, leading to uneven stress on the medial or lateral knee joint.

1. Pain radiation:

• The hip joint shares a common sensory innervation with the knee, particularly through the femoral nerve and obturator nerve. As a result, pain from the hip region can be perceived as knee pain.

1. Gait pattern anomalies:

• Patients with hip dysplasia tend to adjust their gait by adopting a protective posture or increasing pelvic movements, which exacerbates the overloading of the knee region.

Diagnostic Strategies: Finding the Origin of Pain

Clinical examination

• Gait analysis: Abnormalities such as limping or shortened steps provide information about the stress on the hip and knee.
• Palpation: Pain upon pressure on specific areas helps narrow down the focus.

Imaging Techniques

• X-rays: Ideal for detecting osteoarthritis or fractures.
• MRI: Provides detailed images of soft tissues and helps diagnose bursitis or muscle injuries.
• Ultrasound: Particularly useful for visualizing swelling or effusions.

Therapeutic Approaches: Multidisciplinary Solutions

Conservative treatment

• Physical Therapy: The goal is to strengthen and stabilize the muscles to eliminate biomechanical imbalances.
• Pain Therapy: NSAIDs (non-steroidal anti-inflammatory drugs) help reduce acute inflammation.
• Orthopedic aids: Customized shoe inserts or bandages relieve the affected joint.

Surgical Interventions

In some cases, especially with advanced osteoarthritis or severe injuries, surgery is required:

• Hip replacement: Replacing the damaged hip joint reduces secondary knee pain.
• Arthroscopy: Minimally invasive interventions can correct changes in the hip joint.

Prevention: How to prevent knee pain through healthy hips

Regular Exercise

A balanced training program that combines strength, flexibility, and endurance protects both joints.

Ergonomics in Everyday Life

• Proper Sitting: Avoiding prolonged sitting in a flexed position.
• Hip-Friendly Loading: Regularly changing sitting and standing positions.

Nutrition

A diet rich in calcium and vitamin D strengthens bones and joints.

Conclusion

Knee pain should always be considered holistically, as it is not uncommon for it to originate from the hip or other anatomical structures. An accurate diagnosis and collaboration between various specialists are crucial for successful treatment.

By improving awareness of these interconnections, many patients can receive appropriate therapy earlier and avoid long-term complications.