This group consists of patients in the subacute phase post-stroke (1 week to 6 months) who are receiving inpatient treatment at the Istanbul Physical Therapy and Rehabilitation Training and Research Hospital. Ultrasonographic assessment will be performed to determine the structural characteristics of the Tibialis anterior muscle. Measurements will be taken from the mid-belly region where muscle thickness is maximal. The patient will be in a supine position at rest, with the ankle in a neutral position on a stable surface. Pennation angle, muscle fascicle length, and muscle thickness will be measured. Measurements will be repeated three times, and the arithmetic mean of these three measurements will be calculated.

This group consists of patients in the chronic phase post-stroke ( > 6 months) who are receiving inpatient treatment at the Istanbul Physical Therapy and Rehabilitation Training and Research Hospital.

Ultrasonographic assessment will be performed to determine the structural characteristics of the Tibialis anterior muscle. Measurements will be taken from the mid-belly region where muscle thickness is maximal. The patient will be in a supine position at rest, with the ankle in a neutral position on a stable surface. Pennation angle, muscle fascicle length, and muscle thickness will be measured. Measurements will be repeated three times, and the arithmetic mean of these three measurements will be calculated.

The Pennation Angle is the angle formed between muscle fascicles and the deep aponeurosis, serving as a critical determinant of muscle force-generating capacity. Measured via longitudinal ultrasonography on the Tibialis Anterior, this parameter quantifies structural remodeling. In stroke survivors, alterations in this angle reflect muscle atrophy and directly impact functional recovery and gait potential.

Muscle Thickness is defined as the perpendicular distance between the superficial and deep aponeuroses at the widest point of the muscle belly. Measured via ultrasonography on the Tibialis Anterior, it serves as a direct indicator of muscle volume. In stroke survivors, reduced thickness quantifies the extent of muscle atrophy, providing insight into the loss of contractile mass and associated weakness.

Muscle Fascicle Length is defined as the linear distance between the superficial and deep aponeuroses along the muscle fiber path. Assessed via ultrasonography in the Tibialis Anterior, this parameter is a key determinant of muscle shortening velocity and excursion range. In post-stroke patients, shortened fascicles often indicate structural adaptations related to spasticity and reduced functional mobility.

The Brunnstrom Recovery Stage is a standardized clinical tool used to evaluate motor recovery in stroke survivors. It classifies the progression of motor function into six sequential stages, ranging from flaccidity (Stage 1) to isolated, near-normal movement (Stage 6). In this study, it quantifies lower extremity motor impairment to correlate functional recovery status with the structural architectural changes observed in the Tibialis Anterior muscle.