Plantar fasciitis is a common cause of heel pain, and although stretching exercises are a standard first-line treatment, current evidence on adding proprioception or knee-strengthening exercises remains limited. This study investigates whether adding knee strengthening or proprioception exercises to a standard stretching program improves pain, function, and disability in patients with chronic plantar fasciitis, and whether these interventions produce measurable changes in the biomechanical and kinesiological properties of the foot, ankle, and knee.
Age between 18 and 65 years.
Formal diagnosis of plantar fasciitis, characterized by sharp pain during the first steps in the morning, pain that increases with prolonged activity, localized tenderness on palpation of the medial calcaneal tubercle or proximal fascia, and a positive Windlass test.
Symptom duration of at least 3 months.
Heel pain intensity score of Visual Analog Scale (VAS) > 3.
History of acute lower-extremity trauma.
History of prior foot or ankle surgery.
Corticosteroid injection to the affected heel within the preceding 6 months.
Presence of systemic inflammatory or rheumatologic disease.
Parallel
Stretching
Other interventionParticipants will perform standardized plantar fascia and gastrocnemius-soleus stretching exercises. The protocol consists of stretching twice daily, 7 days per week, for 6 weeks.
Proprioception and Stretching Exercises
Other interventionIn addition to the standard stretching protocol, participants in this group will perform a supervised, 6-week progressive proprioception exercise program administered by a physiotherapist three times per week. Exercises will be performed under both eyes-open and eyes-closed conditions on progressively less stable surfaces with task difficulty advanced on a weekly basis.
Knee Strengthening and Stretching Exercises
Other interventionIn addition to the standard stretching protocol, participants in this group will perform a supervised, 6-week progressive knee-strengthening program administered by a physiotherapist three times per week.
Pain Intensity (First-Step Morning, Evening, and Overall Daily Pain)
Pain intensity during the first steps in the morning, before going to bed, and overall daily pain will be assessed using the Visual Analog Scale (VAS). The scale consists of a 10-cm horizontal line ranging from 0 (no pain) to 10 (worst imaginable pain), on which participants mark the point corresponding to their perceived pain level.
Pressure Pain Threshold (PPT)
PPT will be assessed using a Baseline® 12-1442 dolorimeter (22-lb sensitivity range; Fabrication Enterprises Inc., USA) to evaluate deep-tissue mechanical sensitivity. With the participant positioned prone and the feet hanging off the table, gradually increasing pressure will be applied to the midpoint of the plantar fascia insertion at the calcaneus. The pressure at which the participant first perceives pain will be recorded. Three measurements will be taken at 30-second intervals, and the mean value will be used for analysis.
Foot Function and Health Status (Revised Foot Function Index, FFI-R)
The FFI-R is a self-reported, multidimensional questionnaire comprising 68 items across four subscales: pain and stiffness, social and emotional consequences, dysfunction, and activity limitation. Each item is scored from 1 to 4, with higher scores indicating poorer foot health and greater functional limitation.
Foot and Ankle Function (Foot and Ankle Outcome Score, FAOS)
The FAOS is a 42-item self-reported questionnaire assessing five subscales: pain, other symptoms, activities of daily living, sports and recreation, and foot-and-ankle-related quality of life. Each item is scored from 0 to 4.
Myofascial Tissue Biomechanical Properties
The biomechanical and viscoelastic properties of the plantar fascia, Achilles tendon, gastrocnemius medialis, soleus, biceps femoris, semitendinosus, tibialis anterior, vastus lateralis, vastus medialis, and rectus femoris will be assessed non-invasively using the MyotonPRO device (Myoton AS, Tallinn, Estonia). The device will be positioned perpendicular to the anatomical landmark of each muscle; upon delivery of a mechanical impulse, it automatically calculates muscle tone (Hz), stiffness (N/m), and elasticity (logarithmic decrement). The mean of three consecutive measurements will be recorded.
Plantar Fascia Ultrasonographic Parameters
Musculoskeletal ultrasonography (GE Logiq® P5 system; GE Healthcare, USA) will be used to evaluate structural changes. Plantar fascia thickness will be measured longitudinally at 0.5 cm, 1 cm, and 3 cm distal to the calcaneal insertion. Qualitative parameters, including tissue echogenicity, perifascial fluid accumulation, and calcifications, will also be recorded.
Ankle Dorsiflexion Range of Motion (ROM)
Weight-bearing ankle dorsiflexion ROM will be measured in degrees using a Baseline® 12-1057 digital inclinometer (0.1° resolution; Fabrication Enterprises Inc., USA), positioned parallel to the long axis of the tibia over the tibial tuberosity during a weight-bearing lunge test. The mean of three measurements will be recorded.
First Metatarsophalangeal (MTP) Joint Range of Motion
Maximum active dorsiflexion and flexion angles of the first MTP joint will be measured in degrees using a finger goniometer with the participant in a supine position. The mean of three measurements will be recorded.
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