This study was designed to assess the effect of a 12-week hydro-kinetic plyometric (HK-Plyo) training on pain, muscle strength, disability, and quality of life (QoL) in adolescents with patellofemoral pain syndrome (PFPS). Fifty-six adolescents with PFPS were randomly allocated to the HK-Plyo group (n = 28, received the plyometric-based hydro-kinetic therapy program, twice/week, over 12 weeks) or the control group (n = 28, received standard exercise program). Both groups were assessed for pain, muscle strength, disability, and QoL pre and post-treatment.

Fifty-six adolescents diagnosed with PFPS were recruited from three major tertiary-care hospitals in Riyadh, Saudi Arabia. Inclusion criteria comprised individuals aged 10 to 18 years with a confirmed PFPS diagnosis (ICD-10 code: M22.2X9). Participants were required to present with chronic pain (>3 months in duration) scoring greater than 3 on a 0-to-10 numeric pain scale, which was exacerbated by physical activity and alleviated by rest. Exclusion criteria encompassed a history of knee surgery, acute knee trauma, patellar subluxation or dislocation, and the use of corticosteroids or anti-inflammatory medications within the preceding six months.

Outcome Measures

Pain Intensity: Assessed during both rest and physical movement using the 11-point Numerical Pain Rating Scale (NPRS), where 0 indicates "no pain" and 10 indicates "worst pain imaginable."

Muscle Strength: Measured as peak concentric torque (in Newton-meters [Nm]) of the quadriceps and hamstring muscle groups using an isokinetic dynamometer at an angular velocity of 120°/sec and 180°/sec.

Functional Disability: Evaluated using the Patellofemoral Disability Index (PDI), a self-reported questionnaire that measures the degree of functional limitation and difficulty an adolescent experiences when performing daily activities due to knee pain.

Quality of Life (QoL): Assessed using the Arabic version of the MOS 36-Item Short Form Health Survey (SF-36), a standardized patient-reported survey that evaluates physical and mental health components across eight health domains.

Interventions

The HK-Polyo group underwent a structured HK-Plyo program conducted in a water medium (pool). The intervention consisted of 24 total sessions, delivered twice a week for 12 consecutive weeks. Each 45-minute session included a 10-minute aquatic warm-up, a 30-minute core plyometric phase, and a 5-minute cool-down. The core phase consisted of 10 unilateral and bilateral lower-limb plyometric exercises, including variations of hopping, bounding, and jumping. Exercise prescription, progression, and safety parameters strictly adhered to the National Strength and Conditioning Association (NSCA) guidelines and the American Academy of Pediatrics (AAP) safety standards.

The control group underwent a standard, land-based exercise program. The intervention consisted of 24 total sessions, delivered twice a week for 12 consecutive weeks, with each session lasting 45 minutes. The program was multimodal and consisted of lower-limb flexibility exercises, progressive lower-extremity strength training, weight-bearing exercises, proprioceptive training, and balance exercises.

Inclusion Criteria:

1. Age of 10-18 years
2. Verified diagnosis of PFPS based on the ICD classification system (ICD-10 code for PFPS: M22.2X9)
3. Pain more than 3 on (0-10 pain scale).
4. Persistent pain more than 3 months
5. Pain get worse with activities and get better with rest.

Exclusion Criteria:

1. History of knee surgery
2. Recent trauma
3. Corticosteroids or anti-inflammatory medications in the past 6 months
4. Patellar subluxation or dislocation

Individual participant data will not be shared with other researchers in order to strictly protect the privacy and confidentiality of the adolescent participants involved in this study

This was a single-blind protocol. The researcher who collected the data was blind to the allocation of treatment