WHAT IS PHYSICAL REHABILITATION
Physical rehab, also known as functional rehab, is a specialized healthcare field focused on improving, maintaining, or restoring physical strength and mobility. Typically, it helps patients improve or maintain functional abilities, such as activities of daily living (ADLs), and gain greater independence after illness, injury, or surgery. It usually includes passive and active therapies.   The distinction between these two terms essentially comes down to the patients' movement. Active and passive treatment techniques often go hand in hand and may even be used in a single session: passive therapy can warm up muscles and reduce pain, followed by active therapeutic exercise. Patients need a personalized recovery plan that combines both. Passive treatment focuses more on pain relief and applies to patients whose injury or condition causes significant pain and discomfort; their first few therapy sessions may consist primarily of passive treatment. As pain decreases, therapists introduce active therapies. Therapists often use passive and active measures in the same session. During active therapy, many patients will continue to receive passive treatments at the beginning or end of their sessions. The key is to get the right mix of passive and active therapies to best suit their needs. The Physical Therapy page and Exercise Video Library of Veritas Publications offer unbiased, high-quality patient education resources that empower people to make informed health decisions.

PASSIVE THERAPIES 
Treatments that do not require the patient to move their muscles and joints. This may be because the patient is still experiencing excessive pain or discomfort that prevents them from undertaking more active exercises, or because the patient’s muscles are too weak to complete specific exercises.  Passive therapies thus primarily involve pain management to be able to advance to a more active approach eventually. Here are the most common passive therapies used for physical rehab: 
Conductive modalities use thermal conduction to produce local, and occasionally generalized, heating or cooling of superficial tissues, with a maximum penetration depth of 1 cm or less. Two primary conductive modalities are:  
1) Thermotherapy refers to applying therapeutic heat, including warm whirlpool, warm hydrocollator packs, paraffin baths, and fluid therapy. The primary physiological effects of heat include increased blood flow through vasodilation (dilation of blood vessels), increased metabolic rate, and relaxation of muscle spasm. Increasing local tissue temperature accelerates healing by dilating blood vessels and shifting the oxy-hemoglobin dissociation curve, increasing oxygen and nutrient supply to the tissue. Heat can relax muscle tone by reducing muscle spindle and gamma efferent firing rates. Another theory is that muscle relaxation occurs when pain disappears. 
2) Cryotherapy applies therapeutic cold, including ice massage, cold hydrocollator packs, cold whirlpool, cold spray, contrast baths, ice immersion, cold compression, and cryokinetics. The primary physiological effects of cold include decreased blood flow through vasoconstriction (constriction of blood vessels), a decreased metabolic rate, and decreased nerve conduction velocity. Restricting local blood flow reduces the risk of edema (swelling). A slower metabolism releases fewer inflammatory mediators and therefore reduces edema formation. Decreased nerve conduction velocity, an increased threshold for muscle spindle activation, and depressed excitability in free nerve endings increase the pain threshold and, therefore, provide pain relief. 
Electrotherapy uses electrical currents, such as transcutaneous electrical nerve stimulation (TENS) and interferential current (IFC), to relieve pain.  A portable pulse generator delivers electrical currents across the intact skin surface via self-adhesive conducting pads (electrodes). Electrical energy is used for the modulation of pain through stimulation of cutaneous sensory nerves and the following two analgesic mechanisms:  ​
1) Gate Control Theory refers to applying an electrical current to a painful area. This stimulates large-diameter A-beta (Aβ), fast-conducting nerve fibers, which inhibit pain signal transmission to the brain by closing the gate for small-diameter A-delta (Aδ) nerve fibers that carry pain messages to the brain.
2) Endorphin Release Theory refers to the production of endogenous opioids by the brain to modulate pain perception. Endorphins are endogenous transmitters with a similar effect to morphine. The stimulation of A-delta (Aδ) and C fibers causes the release of endorphins (endogenous opioids) that bind to opiate receptors and block the release of “Substance P” (a neurotransmitter involved in pain responses). 
Therapeutic ultrasound is a deep-heating modality that can raise tissue temperature at considerable depth because it travels well through homogeneous tissue (e.g., fat). Physical rehab commonly uses it to provide deep heating to soft tissues (muscles, tendons, joints, and ligaments), and it should not be confused with diagnostic ultrasound, which is used to see inside the body, such as checking on a fetus during pregnancy. Mechanical vibration at increasing frequencies is known as sound energy. The normal human sound range is from 16 Hz to 15-20,000 Hz (in children and young adults). Beyond this upper limit, the mechanical vibration is known as Ultrasound. Therefore,  Ultrasound is a form of mechanical energy. The frequencies used in therapy are typically between 1.0 and 3.0 MHz (1MHz = 1 million cycles per second). Ultrasound delivers pressure waves created by the mechanical vibration of particles through a medium as an uninterrupted stream (continuous mode for chronic conditions) or with periodic interruptions (pulsed mode for acute conditions). Traditionally, it has been used for its thermal effects, but it can enhance healing at the cellular level by altering all phases of tissue repair. Recent studies show that ultrasound-released nitric oxide may be a potent angiogenic (blood vessel formation) agent, stimulating new blood vessel growth at the injury site.  More recently, pulsed ultrasound has been shown to accelerate healing of fresh fractures by enhancing angiogenic (blood vessel formation), chondrogenic (cartilage formation), and osteogenic (bone formation) activity. Ultrasound also helps relieve pain, and the literature proposes reduced pain transmission as a possible mechanism for its analgesic effects. 
Laser therapy is a form of light therapy, and LASER stands for Light Amplification by Stimulated Emission of Radiation. It amplifies light by turning it into a single, concentrated beam with specific properties through a chain reaction of atomic emissions. Laser light follows the fundamental laws of light: it travels in straight lines at a constant velocity. It can be transmitted, reflected, refracted, and absorbed. Its position on the electromagnetic spectrum depends on its wavelength/frequency, which varies by generator. Therapeutic lasers mostly fall into Class 3B or Class 4, depending on their power output. Older or lower-powered therapeutic devices historically used Class 3A (now mostly categorized under Class 1M or 3R) and Class 3B lasers, while modern clinical devices often use Class 4 lasers to achieve deeper tissue penetration and faster treatment times. More recently, the terms Low-Level Laser Therapy (LLLT) and Low-Intensity Laser Therapy (LILT) have been adopted. Lasers with wavelengths ranging from 632 to 904 nm effectively treat musculoskeletal disorders.  As with many other forms of energy delivered to the patient, the primary effects are divided into thermal and non-thermal. LLLT is generally considered a non-thermal energy application. However, the body's delivery and absorption of energy will produce some heat. So, non-thermal, in this context, refers to the non-accumulative nature of thermal energy. While some studies show that LLLT can result in immediate pain reduction in rheumatoid arthritis (RA), osteoarthritis (OA), tendinopathies, acute and chronic neck pain, temporomandibular joint (TMJ) pain, and other joint disorders, there is currently a lack of consensus on the best parameters to use; i.e., power, dosage, time, pulsing, and type of laser.  The therapeutic wavelength appears to be between 800 and 1,000 nm, and the dose is around 6-10 joules/cm2. Light at the wavelength typically employed in laser therapy is readily absorbed by enzymes, hemoglobin, fibroblasts, and neurologic tissue. Laser has been shown to stimulate cell degranulation, releasing potent inflammatory mediators such as growth factors, and to activate fibroblast function, thereby increasing collagen deposition and improving tensile strength. Some reports also show a slight decrease in inflammation-induced edema following laser therapy.  Hemoglobin-mediated absorption releases nitric oxide, resulting in endothelial cell proliferation.   Low dosages also significantly decrease sensory nerve conduction velocity, reducing pain. LLLT may reduce inflammation-related pain by lowering COX-2 and tumor necrosis factor-alpha (enzymes associated with inflammation), as well as oxidative stress, edema, and bleeding.  It may also increase mitochondrial ATP production, a cell’s basic energy currency, thereby increasing metabolic activity. 
1) Class 3B Lasers are traditional "cold lasers" or "soft lasers" that typically operate with a power output between 5 milliwatts (mW) and 500 mW. They are safe for the skin because they produce little heat, making them popular for superficial wound healing, arthritic joint treatment, and physical therapy. However, they require longer treatment times to deliver an effective dose to deeper tissues.
2) Class 4 Lasers are high-power therapeutic lasers with an output exceeding 500 mW. Often called "Class IV laser therapy" or "high-intensity laser therapy (HILT)," they can quickly deliver a therapeutic dose of light energy to deep-seated muscles, ligaments, and joints. Because they generate noticeable heat, clinicians must keep the laser head moving during treatment to prevent burns.
Both Class 3B and Class 4 therapeutic lasers pose a significant risk of permanent eye damage if viewed directly or via reflective surfaces. For this reason, both the clinician and the patient must wear specialized, wavelength-specific safety goggles during every treatment session.
Passive exercises, also known as passive range of motion (ROM), refer to how far a joint can move in different directions. These exercises are considered passive because the patient exerts no effort. Instead, someone helps move the patient's muscles and joints through their full range of motion. Therapists can also perform passive ROM alongside passive stretching exercises, in which the therapist stretches the patient's soft tissues (muscles, tendons, and ligaments). Passive ROM exercises can help prevent muscle stiffness and spasm. In addition to prevention, passive ROM exercises can treat spasticity.  

ACTIVE THERAPIES
Any treatment where the patients are physically involved. This might mean they are moving a joint or muscle, either with a therapist's assistance or without. If the patients are physically involved in the treatment in any way, the treatment is considered active. An active rehab program is provided for those patients who no longer require acute care treatment but have ongoing physical complaints with respect to their original injuries. These patients have typically plateaued with conventional therapies and require a more active approach to their recovery.   Active therapies always involve exercise focusing on restoring and maintaining flexibility, strength, endurance, stability, and balance. Active therapeutic exercises aim to return an injured patient to full function without pain. Therapeutic exercises fall into four basic categories:  
Flexibility exercises are stretching and ROM exercises to improve patients' flexibility.  Flexibility exercises give patients greater freedom of movement for their physical and everyday activities, such as getting dressed and reaching for objects on a shelf. There are different types of flexibility exercises performed by the patients based on their stage of recovery: 
1) Active-assistive ROM exercises involve some assistance from the therapist. The patient can move their limb but cannot achieve the full range of motion due to weakness or pain. This helps slowly increase the strength of the patient's specific muscle. 
2) Active ROM exercises involve the patient performing all movements without manual assistance from the therapist. The therapist may continually provide verbal cues to help the patient perform the exercises correctly. 
3) Stretching exercises are for patients with limited ROM and/or flexibility who often need to begin stretching exercises. Stretching exercises can recondition muscles that have contracted due to injury or other trauma. By keeping muscles stretched and loose, the patient can maintain flexibility and reduce the risk of reinjury or loss of range of motion. 
Strengthening exercises are for patients with muscle weakness, a common problem with age, injury, and surgery. The human body is resilient, and proper exercise can improve muscle strength. By increasing muscle strength, patients can improve balance and mobility and enjoy a normal lifestyle. Strengthening exercises don't require lifting weights or starting a heavy workout program. Simple exercises, such as toe raises, leg lifts, and arm rotations, can improve muscle strength and endurance. Some therapists recommend using resistance bands, light weights, or other tools for advanced muscle strengthening.
Endurance exercises, also known as aerobic activities, include brisk walking, jogging, swimming, and playing sports (e.g., tennis, soccer). They increase breathing and heart rate, help keep patients healthy, improve fitness, and enable them to do everyday tasks. Endurance exercises improve heart, lung, and circulatory health. They also delay or prevent many diseases that are common in older adults, such as diabetes, heart disease, and osteoporosis. 
Balance exercises can help prevent falls and reduce the risk of resulting disability. They can also help people with balance issues, such as after a stroke or with muscle weakness. Initially, a therapist can help the patient perform balance exercises on parallel bars. This depends largely on the patient's balance level. They can be transitioned to exercises without the bars as soon as the patient can perform them without the therapist's help. At this stage, the patient may proceed to more complex movements such as heel-to-toe walking and standing on one foot.