Whole-Body Vibration in Patients With Patellofemoral Pain Syndrome

Efficacy of Whole-Body Vibration in Patients With Patellofemoral Pain Syndrome: A Prospective, Randomized, Double-Blind, Placebo-Controlled Clinical Trial

Patellofemoral Pain Syndrome (PFPS), or anterior knee pain, is one of the most common disorders affecting the lower extremities.

Currently, there is no established "gold standard" treatment for PFPS. However, various interventions-including strengthening of the hip and knee muscles (e.g., hip abductors, external rotators, and knee extensors), taping, bracing, foot orthoses, manual therapy, acupuncture, blood flow restriction training, and conventional physical agents (e.g., ultrasound, cryotherapy, neuromuscular electrical stimulation, laser therapy, electromyographic biofeedback, etc.)-have been reported to provide meaningful clinical benefits. Strengthening of the hip and knee muscles alone has been shown to improve both pain and function in the short, medium, and long term. In recent high-quality studies, hip and knee muscle strengthening has been recognized as an effective "classical" treatment approach for PFPS. Regarding the mechanism of pain relief, previous research suggests that strengthening these muscles may alleviate pain by stabilizing patellar motion and/or reducing pressure on the patellofemoral joint.

Similar to traditional resistance training, whole-body vibration (WBV) training is an alternative method for muscle strengthening. WBV platforms can generate vertical vibrations that stimulate tonic vibration reflexes through muscle spindles, thereby activating homonymous alpha motor neurons and inducing reflex muscle contractions. As a result, increased motor unit recruitment enhances the excitability of muscle spindles, leading to improved muscle strength. Additionally, WBV training can improve muscle balance, strength, and function. Therefore, combining WBV with hip and knee strengthening exercises may represent a more effective treatment strategy for PFPS. The aim of this study is to evaluate whether the combination of WBV and hip-knee muscle strengthening is more effective in reducing pain and improving function than hip-knee strengthening alone.

Patellofemoral Pain Syndrome (PFPS), or anterior knee pain, is one of the most common disorders affecting the lower extremities.

Currently, there is no established "gold standard" treatment for PFPS. However, various interventions-including strengthening of the hip and knee muscles (e.g., hip abductors, external rotators, and knee extensors), taping, bracing, foot orthoses, manual therapy, acupuncture, blood flow restriction training, and conventional physical agents (e.g., ultrasound, cryotherapy, neuromuscular electrical stimulation, laser therapy, electromyographic biofeedback, etc.)-have been reported to provide meaningful clinical benefits. Strengthening of the hip and knee muscles alone has been shown to improve both pain and function in the short, medium, and long term. In recent high-quality studies, hip and knee muscle strengthening has been recognized as an effective "classical" treatment approach for PFPS. Regarding the mechanism of pain relief, previous research suggests that strengthening these muscles may alleviate pain by stabilizing patellar motion and/or reducing pressure on the patellofemoral joint.

Similar to traditional resistance training, whole-body vibration (WBV) training is an alternative method for muscle strengthening. WBV platforms can generate vertical vibrations that stimulate tonic vibration reflexes through muscle spindles, thereby activating homonymous alpha motor neurons and inducing reflex muscle contractions. As a result, increased motor unit recruitment enhances the excitability of muscle spindles, leading to improved muscle strength. Additionally, WBV training can improve muscle balance, strength, and function. Therefore, combining WBV with hip and knee strengthening exercises may represent a more effective treatment strategy for PFPS. The aim of this study is to evaluate whether the combination of WBV and hip-knee muscle strengthening is more effective in reducing pain and improving function than hip-knee strengthening alone.

Inclusion Criteria:

• Aged between 18 and 40 years,
• Diagnosed with unilateral Patellofemoral Pain Syndrome (PFPS),
• Reporting anterior knee pain or pain behind the patella in at least two of the following activities:

ascending stairs, jumping, running, squatting, kneeling, prolonged sitting,

- Positive results in at least two of the following clinical tests: Eccentric step-down test, Patellar border tenderness test, Patellar grind (Clarke's) or apprehension test,

• Ability to understand the procedures, potential benefits, and possible adverse effects,
• Willingness to participate in the treatment program.

Exclusion Criteria:

• Severe injury or pathological changes in knee structures (e.g., ligaments, menisci, patellar tendons, iliotibial bands, joint capsules, or plicae),
• History of significant trauma or surgery involving the knee or lower extremity,
• History of patellar dislocation or subluxation,
• Diagnosis of Osgood-Schlatter disease or Sinding-Larsen-Johansson syndrome,
• Joint effusion in the knee, or presence of redness, swelling, or increased warmth on physical examination,
• Serious systemic conditions, including cardiovascular diseases, tumors, gallstones or kidney stones, severe disc or spinal lesions, pacemaker implantation, epilepsy, recent fractures or surgeries, or acute arthritis,
• Pregnancy.