Sprains and strains are similar in that they are both injuries that commonly occur during sports, exercise, or other physical endeavours.

Sprains are defined as stretch tears to ligaments, which are the bands of dense regular connective tissue that connect bones to each other.

Strains, on the other hand, are defined as stretch-induced tears to tendons or skeletal muscles.  Tendons are similar to ligaments in composition, comprised of bundles of ropy collagen proteins, elastic protein fibers (e.g., fibrillin, elastin) as well as specialized fibroblasts and proteoglycans.  Tendons are classified as dense regular connective tissue, and function as resilient, stretchy connections that anchor skeletal muscles to bone.

In addition to sports, age can be a risk factor due to age-related decrease in collagen elasticity, as well as age-related atrophy of supportive muscles (i.e., sarcopenia) as can sedentary behaviour for the same reason.  Acute trauma (e.g., vehicle or workplace accidents) is also a risk factor.  Ensuring workplace safety and ergonomic work settings for employees can reduce the risk of musculoskeletal injuries.  Predisposing factors include body weight due to load on joint tissues, and poor diet as it can contribute to suboptimal health of tissues.

It is estimated that injuries to ligaments and strains account for 50% of musculoskeletal injuries in North America each year.

Common Locations – Sprains and Strains

Sprains most often involve the ligaments of the knee, elbow, wrists, and ankles.

Examples of Sprains:

Ankle sprains are amongst the most common sprain and occur when rolling the ankle while running, walking, jumping, or other movement that results in an awkward landing.  Uneven surfaces and sports that involve pivoting (e.g., volleyball, dance, basketball, figure skating) are risk factors.  Ankle sprains most often involve an inversion twist of the foot and can involve one or more ligaments within the ankle joint.

Repeated throwing can lead to elbow sprains of the ulnar collateral ligament.

Soccer, skiing, and other sports that involve quick twisting movements or contact are risk factors for tears in the anterior cruciate ligament (ACL), posterior cruciate ligament (PCL), lateral collateral ligament (LCL) and medial collateral ligament (MCL) tears in the knee joint. Injuring any combination of these ligaments and either or both menisci of the knee is sometimes called the “terrible/unhappy triad” or “blown knee” (most often involving the ACL, MCL, and medial meniscus).  Biological sex is thought to be a risk factor for knee injuries, with females more at risk than males due to the wider Q-angle (angle between patella and superior iliac spine) which affects the direction of body weight and forces exerted on the knee.  The Q-angle for adult females is approximately 17º and the Q-angles for adult males is approximately 14º.

Strains most often involve the tendons of the hands, feet, knees, biceps, triceps, quadriceps, hamstrings, ankles and Achilles heel tendon.

Examples of Strains:

Tennis elbow (e.g., lateral epicondylitis)

Golfer’s and baseball elbow (e.g., medial epicondylitis)

Jumper’s knee (e.g., patellar tendonitis)

Groin pull (due to a tear of one of the muscles within the groin)

Signs and Symptoms – Sprains and Strains

Both sprains and strains typically result in inflammation (swelling, pain, warmth and redness), tenderness and may cause muscle spasms, loss of joint stability, decreased strength and changes in range of motion.  Locking of joints may occur due to muscle spasms, pain or the lodging of tissue debris within the joint.  Alternatively decreased joint stability can occur with torn ligaments, tendons or muscles.  Additionally, joint dislocation or subluxation may have occurred at the same time.

Severity Levels – Sprains and Strains

Both sprains and strains are graded based on the severity of damage ranging from micro-trauma (micro-tears) to complete tears.

First degree (or grade 1) sprains and strains involve mild stretching of collagen fibers (of ligament/tendon) or muscle tissue respectively.  First degree injuries are often able to heal on their own within 2 weeks.

Second degree (or grade 2) sprains and strains involve moderate tearing of collagen fibers (of ligament/tendon) or muscle tissue respectively.

Third degree (or grade 3) sprains and strains involve complete tearing of collagen fibers (of ligament/tendon) or muscle tissue respectively, and is often accompanied by a “snapping sound”.

Diagnosis – Sprains and Strains

Diagnosis of both sprains and strains typically involve physical examinations and imaging (e.g., MRI) when necessary.  Arthrography using radio-dense dye (e.g., iodine) or MRI contrast medium to view the injury using x-rays or MRI respectively can be helpful in assessing damage and planning treatment.

Treatment – Sprains and Strains

Treatment of open wounds (if present) involves cleaning and controlling any bleeding as well as ensuring stability of the individual’s vital signs.

Treatment of sprains and strains depends on the severity of the injury.  Ensuring vascular perfusion and treatment of any dislocations as well as removing any debris and treating any infection is required.

Treatment of mild and moderate sprains and strains usually involves PRICE (Protection, Rest, Ice, Compression, Elevation) for the first 48 to 72 hours, followed by alternate heat and cold, compression bracing, and rehabilitation exercises.  Anti-inflammatories may be used immediately after the injury to reduce swelling and pain.  Rehabilitative therapies are recommended as healing progresses to regain strength, flexibility and range of motion.

Arthroscopy can be helpful in allowing for viewing and repairing ligament, tendon and muscle tears.  Complete tears typically can’t heal on their own will require surgical repairs.  For example, complete ACL tears may involve autografts using hamstring tendon, allografts (from anatomical donor), or even synthetic grafts.

Treatments such as biophysical stimulation can sometimes be used to promote healing.  These methods include cryotherapy, ultrasound, growth factor or platelet-rich plasma injections and physical therapy.  Experimental injections of mesenchymal stem cells may be beneficial though more research is required.

Three Stages of Healing – Sprains and Strains

Initially, a period of inflammation will occur, followed by a period of proliferation and remodeling.

Inflammatory Stage – during this stage, cellular damage induces white blood cells (WBCs) such as macrophages, and mast cells to release pro-inflammatory cytokines (e.g., histamine, prostaglandins, bradykinin) which stimulate vasodilation, capillary permeability and exudate formation.  The signs and symptoms of inflammation (swelling, pain, redness and warmth) will be present as a result.  WBCs such as neutrophils and macrophage phagocytose debris and platelets form clots to seal off any damaged blood vessels to stop bleeding.  This stage will overlap with the next stage.

Proliferation Stage – during this stage, platelets, and other cells release growth factors which stimulate proliferation of the specialized fibroblasts that play key roles in producing collagen, elastic fibers and the proteoglycan and fluid extracellular matrix of tendons and ligaments.  Initially this material will not be arranged to optimally support strength and this stage will overlap with the next stage.

Remodeling Stage -during this stage the collagen and extracellular matrix is re-arranged to replace damaged components which have been removed and recycled by phagocytes.  Blood vessels will have been repaired

Potential Complications

Due to the low levels of vascularization of ligaments and tendons, full recovery of moderate or severe sprains is usually not expected and the healing that does occurs slowly.   Full tears, are not able to self-heal and either suturing or grafting is required.  Suturing skeletal muscle is challenging and there is a likelihood will all moderate to severe tears in the formation of scar tissue and at times dystrophic calcification.  Scar tissue is problematic in that it is weaker and less stretchy that the original tissue contributing to loss of strength, elasticity and range of motion within the affected structure.

Myositis Ossificans

Myositis Ossificans (MO) is a potential complication of muscle injuries and can become noticeable 3 months or more post-injury.  MO occurs when calcium is inappropriately deposited into skeletal muscle tissue that has been damaged, and becomes a hard bone-like structure, that causes pain.  MO more commonly occurs within contusions of the quadriceps or muscles of the upper arm.  Football players being at particular risk due to the risk of contusions in those regions.  It has been estimated that 9-20% of quadriceps muscle contusions lead to MO