A femoral neck stress reaction refers to an early stage of bone injury where the bone exhibits changes due to overuse or repetitive stress but has not yet fully fractured. It is often characterised by bone marrow edema (swelling) and microfractures within the bone, which are visible on imaging such as MRI. Femoral neck stress fractures, on the other hand, occur when these microfractures progress to a complete break in the bone. Stress fractures can be either non-displaced, where the bone cracks but remains in alignment, or displaced, where the bone fragments shift out of place, requiring surgical intervention.

Tension femoral neck stress fractures arise from the tension forces at the superior aspect of the femoral neck. While normally counterbalanced by the forces of the gluteus medius and minimus, when these muscles fatigue, high tension forces develop across the superior femoral neck on load bearing. This results in microfracture formation and propagation with subsequent fracturing of the superior aspect of the femoral neck. Such a fracture line propagates at 90 degrees to the broken cortex, creating a transverse fracture, which is more unstable than that of the compression fracture, with a higher likelihood of displacement. Note that altered hip geometry such as coxa vara can decrease the efficiency of the gluteal muscles, promoting early fatigue of these muscles and development of tension-sided femoral neck stress reactions or fractures. 

Femoral neck stress reactions and fractures are often caused by a combination of high-impact activities, inadequate recovery, and biomechanical issues. The following factors are commonly associated with the condition:

• Overuse and repetitive loading: Athletes involved in running, dancing, and sports that involve repetitive high-impact movements are at a higher risk.
• Rapid increases in training intensity or volume: A sudden increase in the intensity or frequency of physical activity without adequate rest can lead to stress reactions in the femoral neck.
• Biomechanical abnormalities: Issues such as poor alignment, leg length discrepancies, and hip muscle imbalances can increase the risk of femoral neck stress injuries by altering the distribution of forces through the hip joint.
• Low bone density: Conditions like osteoporosis, female athlete triad, or aging can make bones more susceptible to stress fractures.

Previous injury: A history of prior fractures or other stress injuries increases the likelihood of reinjury, especially if the rehabilitation process is not adequately followed.

The symptoms of a femoral neck stress reaction or fracture often begin gradually and can worsen over time:

• Pain in the groin, hip, or thigh, which may initially occur only with activity but progressively worsen with continued loading.
• Tenderness over the femoral neck when palpated.
• Pain with weight-bearing: In the case of a stress reaction, pain may be noticeable during walking or running, and in more severe cases, the pain may persist even at rest.
• Reduced range of motion in the hip joint, particularly with activities such as turning or pivoting.

Difficulty with walking and a noticeable limp, which may occur if the stress reaction progresses to a full fracture.

Diagnosing femoral neck stress reactions and fractures involves a combination of clinical evaluation and imaging. X-rays may be used initially, but MRI or bone scans are more sensitive for detecting stress reactions, as they can identify early bone changes that are not visible on X-rays. A CT scan may be employed to assess the extent of a fracture, particularly in cases where surgical intervention is considered.

In a clinical setting, a hop test can aid in the diagnosis or suspicion of femoral neck stress reactions and fractures. A hop test, or single leg hop test, may reveal or reproduce pain and should be used with other clinical assessments and diagnostic imaging. In addition to the hop test, someone who is suspected of having a femoral neck stress fracture will experience pain with deep palpation over the femoral neck, pain in hip rotation and produce a positive log roll test.

The management of femoral neck stress reactions and fractures primarily involves activity modification, pain management, and a progressive rehabilitation program to promote healing and restore strength. An evidence-based physiotherapy approach focuses on the following treatment strategies:

1. Rest and Activity Modification

In the acute phase, it is crucial to allow the femoral neck to heal. Rest from weight-bearing activities is essential to prevent further damage and give the bone time to recover. For stress reactions, the use of crutches or a fracture brace may be recommended to offload the affected leg. The intensity and volume of physical activity should be gradually reintroduced as symptoms improve.

2. Pain Management

In the initial phase of treatment, modalities such as ice therapy and electrotherapy (TENS) can be used to reduce inflammation and pain. These techniques are particularly helpful during the acute phase of a stress reaction or fracture, helping to manage discomfort and improve the patient’s ability to tolerate rehabilitation exercises.

3. Progressive Strengthening Exercises

As the bone begins to heal, strengthening exercises for the hip and core muscles are essential to support the femoral neck and improve overall stability. Isometric exercises and low-load strength training are introduced initially to avoid stressing the femoral neck. Once healing progresses, eccentric and concentric exercises targeting the hip abductors, gluteals, quadriceps, and core stabilizers are gradually incorporated.

4. Biomechanical Correction

To reduce the risk of re-injury, physiotherapists may address underlying biomechanical issues such as abnormal gait patterns, hip muscle imbalances, and poor alignment. Orthotics may be recommended for patients with leg length discrepancies or overpronation, while proper footwear is essential to support normal movement mechanics during activity.

5. Load Management and Gradual Return to Activity

Once the femoral neck is sufficiently healed, physiotherapists play a key role in facilitating the gradual return to sport or other physical activities. A structured return-to-play protocol involves progressive loading of the bone through weight-bearing activities, including controlled walking, cycling, and eventually running. The emphasis is on gradual progression to avoid overloading the femoral neck too soon.

6. Education and Prevention

Patient education is a vital component of the rehabilitation process. Athletes and active individuals should be educated about proper training techniques, rest, and nutrition (including bone health support through adequate calcium and vitamin D intake). Developing a long-term exercise plan focused on strengthening and flexibility can help prevent future stress injuries.