General Observations and Deformities
Before moving into active testing, the clinician should perform general observations to identify swelling, deformity, discoloration, or muscle atrophy/hypertrophy. Leg positioning can also provide immediate clues to serious injury; for example, an internally rotated leg may suggest hip dislocation, while an externally rotated leg that appears shorter may indicate a femoral neck fracture.
The clinician must also evaluate the patient's posture and alignment, looking at the hip, knee, and foot:
- Hip Alignment: Assessing for Coxa Vara, Coxa Valga, Femoral Anteversion, or Femoral Retroversion.
- Knee/Foot: Observing for Genu Varum, Genu Valgum, Genu Recurvatum, Pes Planus, or Pes Cavus.
Understanding Angles of Inclination and Torsion
Two critical measurements define the biomechanics of the hip: the angle of inclination and the angle of torsion.
1. Angle of Inclination
This is the angle between the femoral neck and the femoral shaft. The normal value is approximately 125∘.
- Coxa Valga: An angle greater than 125∘, often associated with Genu Varum.
- Coxa Vara: An angle less than 125∘, often associated with Genu Valgum.
2. Angle of Torsion
This refers to the angle of the femoral head relative to the femoral shaft.
- Femoral Anteversion: An increased angle, which may cause "in-toeing" or "pigeon toes".
- Femoral Retroversion: A decreased angle, which may lead to "out-toeing" (external rotation) during standing or walking.
Gait Analysis
Observing how a patient walks can reveal significant underlying pathology. Two primary gait abnormalities to look for are:
Antalgic Gait
This is a gait abnormality caused by pain. It is characterized by a shortened stance phase on the affected side to minimize weight-bearing time. Notably, pathologies amenable to hip arthroscopy do not typically result in a severely antalgic gait.
Trendelenburg Gait
Unlike the antalgic gait, Trendelenburg gait is secondary to abductor weakness (specifically the Gluteus Medius) rather than pain. When the patient places weight on the affected leg, the pelvis drops on the contralateral (unsupported) side. Patients may compensate by leaning their upper torso over the affected leg to reduce the demand on the hip abductors.
Special Tests and Range of Motion
Once observations are complete, the clinician moves to active (AROM), passive (PROM), and resisted (RROM/MMT) testing.
Flexibility and Muscle Tightness
Several specialized tests are used to isolate specific muscle groups:
- Modified Thomas Test: Assesses for hip flexor or rectus femoris tightness. A positive test occurs if the thigh cannot lie flat on the table or if the knee cannot remain flexed at 90∘.
- Ely’s Test: Performed in the prone position to test for tight rectus femoris; a positive test is indicated by hip hiking on the ipsilateral side.
- Straight Leg Raise: Tests for hamstring tightness; an inability to reach 70∘ of hip flexion is considered positive.
- Tripod Sign: Performed while seated; if the patient must lean back on their arms to extend the knee, it indicates hamstring tightness.
- Ober’s Test: Used to assess ITB/TFL tightness (though recent research suggests it may better assess general hip abductor tightness).
Muscle Strength (MMT)
Manual Muscle Testing should be performed for all major hip stabilizers and movers, including the Psoas Major, Gluteus Medius, Gluteus Maximus, Adductors, and the various hamstring muscles.
Neurological Screening
To ensure that hip pain is not actually referred from the spine, a neurological exam is necessary. This includes testing:
- Dermatomes: L1–L3.
- Myotomes: L1–L3.
- Reflexes: Specifically the Patellar Tendon Reflex (L3–L4).
By integrating these findings—from the specific location of pain to the mechanical nuances of gait and torsion—the clinician can effectively differentiate between intra-articular hip issues, muscular thigh pathology, and referred lumbosacral pain.
