Symptoms can vary from aches or pains and local joint stiffness, to a burning that surrounds the whole joint around the inflamed tendon. In some cases, swelling occurs along with heat and redness, and there may be visible knots surrounding the joint. With this condition, the pain is usually worse during and after activity, and the tendon and joint area can become stiff the following day as muscles tighten from the movement of the tendon. Many patients report stressful situations in their life in correlation with the beginnings of pain which may contribute to the symptoms.

If the symptoms of tendinitis last for several months (6 months) or longer, it is probably tendinosis.

Symptoms can vary from an ache or pain and stiffness to the local area of the tendon, or a burning that surrounds the whole joint around the affected tendon. With this condition, the pain is usually worse during and after activity, and the tendon and joint area can become stiffer the following day as swelling impinges on the movement of the tendon. Many patients report stressful situations in their life in correlation with the beginnings of pain, which may contribute to the symptoms.

Swelling in a region of micro damage or partial tear may be detected visually or by touch.

Tendinitis injuries are common in the upper shoulder and lower section of the elbow (including the rotator cuff attachments), and are less common in the hips and torso. Individual variation in frequency and severity of tendinitis will vary depending on the type, frequency and severity of exercise or use; for example, rock climbers tend to develop tendinitis in their fingers or elbows, swimmers in their shoulders. Achilles tendinitis is a common injury, particularly in sports that involve lunging and jumping, while Patellar tendinitis is a common among basketball and volleyball players owing to the amount of jumping and landing.

A veterinary equivalent to Achilles tendinitis is bowed tendon, tendinitis of the superficial digital tendon of the horse.

Pain is often aggravated by elevation of the arm above shoulder level or by lying on the shoulder. Pain may awaken the patient from sleep. Other complaints may be stiffness, snapping, catching, or weakness of the shoulder.

Jumper's knee (patellar tendinopathy, patellar tendinosis, patellar tendinitis) commonly occurs in athletes who are involved in jumping sports such as basketball and volleyball. Patients report anterior knee pain, often with an aching quality. The symptom onset is insidious. Rarely is a discrete injury described. Usually, involvement is infrapatellar at or near the infrapatellar pole, but it may also be suprapatellar.

Depending on the duration of symptoms, jumper's knee can be classified into 1 of 4 stages, as follows:

Stage 1 – Pain only after activity, without functional impairment

Stage 2 – Pain during and after activity, although the patient is still able to perform satisfactorily in his or her sport

Stage 3 – Prolonged pain during and after activity, with increasing difficulty in performing at a satisfactory level

Stage 4 – Complete tendon tear requiring surgical repair

It begins as inflammation in the patellar tendon where it attaches to the patella and may progress by tearing or degenerating the tendon. Patients present with an ache over the patella tendon. Most patients are between 10 and 16 years old. Magnetic resonance imaging can reveal edema (increased T2 signal intensity) in the proximal aspect of the patellar tendon.

Tendinosis, sometimes called chronic tendinitis, chronic tendinopathy, or chronic tendon injury, is damage to a tendon at a cellular level (the suffix "osis" implies a pathology of chronic degeneration without inflammation). It is thought to be caused by microtears in the connective tissue in and around the tendon, leading to an increase in tendon repair cells. This may lead to reduced tensile strength, thus increasing the chance of tendon rupture. Tendinosis is often misdiagnosed as tendinitis because of the limited understanding of tendinopathies by the medical community. Classic characteristics of "tendinosis" include degenerative changes in the collagenous matrix, hypercellularity, hypervascularity, and a lack of inflammatory cells which has challenged the original misnomer "tendinitis".

Symptoms may occur immediately after trauma (acute) or develop over time (chronic).

Acute injury is less frequent than chronic disease, but may follow bouts of forcefully raising the arm against resistance, as occurs in weightlifting, for example. In addition, falling forcefully on the shoulder can cause acute symptoms. These traumatic tears predominantly affect the supraspinatus tendon or the rotator interval and symptoms include severe pain that radiates through the arm, and limited range of motion, specifically during abduction of the shoulder.

Chronic tears occur among individuals who constantly participate in overhead activities, such as pitching or swimming, but can also develop from shoulder tendinitis or rotator cuff disease. Symptoms arising from chronic tears include sporadic worsening of pain, debilitation, and atrophy of the muscles, noticeable pain during rest, crackling sensations (crepitus) when moving the shoulder, and inability to move or lift the arm sufficiently, especially during abduction and flexion motions.

Pain in the anterolateral aspect of the shoulder is not specific to the shoulder, and may arise from, and be referred from, the neck, heart or gut.

Patient history will often include pain or ache over the front and outer aspect of the shoulder, pain aggravated by leaning on the elbow and pushing upwards on the shoulder (such as leaning on the armrest of a reclining chair), intolerance of overhead activity, pain at night when lying directly on the affected shoulder, pain when reaching forward (e.g. unable to lift a gallon of milk from the refrigerator). Weakness may be reported, but is often masked by pain and is usually found only through examination. With longer-standing pain, the shoulder is favored and gradually loss of motion and weakness may develop, which, due to pain and guarding, are often unrecognized by the patient and only brought to attention during examination.

Primary shoulder problems may cause pain over the deltoid muscle intensified by abduction against resistance - the impingement sign. This signifies pain arising from the rotator cuff, but cannot distinguish between inflammation, strain, or tear. Patients may report that they are unable to reach upwards to brush their hair or to lift a food can from an overhead shelf.

Many rotator cuff tears are asymptomatic. They are known to increase in frequency with age and the most common cause is age-related degeneration and, less frequently, sports injuries or trauma. Both partial and full thickness tears have been found on "post mortem" and MRI studies in those without any history of shoulder pain or symptoms. However, the most common presentation is shoulder pain or discomfort. This may occur with activity, particularly shoulder activity above the horizontal position, but may also be present at rest in bed. Pain-restricted movement above the horizontal position may be present, as well as weakness with shoulder flexion and abduction.

Patellar tendinitis (patellar tendinopathy, also known as jumper's knee), is a relatively common cause of pain in the inferior patellar region in athletes. It is common with frequent jumping and studies have shown it may be associated with stiff ankle movement and ankle sprains.

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Tendinopathy refers to a disease of a tendon. The clinical presentation includes tenderness on palpation and pain, often when exercising or with movement.

Three terms have evolved in the medical terminology to refer to injuries that cause tendon pain:

- Tendinitis - acute tendon injury accompanied by inflammation

- Tendinosis - chronic tendon injury with degeneration at the cellular level and no inflammation

- Paratenonitis - Inflammation of the outer layer of the tendon (paratenon) alone, whether or not the paratenon is lined by synovium

- Paratenonitis with tendinosis - Paratenonitis associated with intratendinous degeneration

- Tendinopathy - chronic tendon injury with no implication about etiology

Tendon injuries arise from a combination of intrinsic and extrinsic factors; acute tendon injuries may be predominantly caused by extrinsic factors, whereas in overuse syndromes as in the case of tendinopathy it may be caused by multifactorial combinations of both intrinsic and extrinsic factors. An example of an intrinsic factor for tendinopathies are: poor biomechanics such as limb malalignments and hyperpronation that may cause increased traction loads acting on the foot and ankle that may increase the incidence of Achilles, flexor hallucis longus muscle, and tibialis posterior muscle tendinopathies.

Tennis elbow or lateral epicondylitis is a condition in which the outer part of the elbow becomes sore and tender at the lateral epicondyle. The forearm muscles and tendons become damaged from repetitive overuse. This leads to pain and tenderness on the outside of the elbow.

Any activity, including playing tennis, that involves repetitive use of the extensor muscles of the forearm can cause acute or chronic tendonitis of the tendinous insertion of these muscles at the lateral epicondyle of the elbow. The condition is common in carpenters and laborers who swing a hammer or other tool with the forearm, and is similar to golfer's elbow, which affects the medial epicondyle on the inside of the elbow. Continuing activity after onset of the condition and avoiding mandatory rest may lead to permanent onset of pain and only treatable via surgery.

Trapeziometacarpal osteoarthritis, also known as carpometacarpal (CMC) osteoarthritis (OA) of the thumb or osteoarthritis at the base of the thumb, is a reparitive joint disease affecting the first carpometacarpal joint (CMC1). This joint is formed by the trapezium bone of the wrist and the first metacarpal bone of the thumb. Because of its relative instability, this joint is a frequent site for osteoarthritis. Carpometacarpal osteoarthritis (CMC OA) of the thumb occurs when the cushioning cartilage of the joint surfaces wears away, resulting in damage of the joint.

The main complaint of patients is pain. Pain at the base of the thumb occurs when moving the thumb and might eventually persist at rest. Other symptoms include stiffness, swelling and loss of strength of the thumb. Treatment options include conservative and surgical therapies.

The primary and most common symptom in patients with CMC OA of the thumb is pain. Pain at the base of the thumb is mainly experienced when moving the thumb or when applying pressure with the thumb. However, in advanced stages of CMC OA, pain might persist at rest. Another prominent symptom is loss of strength of the thumb. Patients struggle to grab or hold an object due to weakening of the thumb. For example, tying a knot or holding a saucepan becomes increasingly difficult.

If patients present themselves with similar symptoms, physicians should also consider De Quervain syndrome, rheumatoid arthritis or flexor carpi radialis and flexor pollicis longus tendinopathy as a possible cause.

Typical signs of CMC OA can be observed from the outside of the hand. For example, the area near the base of the thumb can be swollen and could appear inflamed. Advanced stages of CMC OA can eventually lead to deformity of the thumb. This deformity, also called a ‘zigzag’ deformity, is characterized by a deviation of the thenar eminence towards the middle of the hand, whilst the thumb phalanges overextend. Also a grinding sound, known as crepitus, can be heard when the CMC1 joint is moved.

Calcific tendinitis is a form of tendinitis, a disorder characterized by deposits of hydroxyapatite (a crystalline calcium phosphate) in any tendon of the body, but most commonly in the tendons of the rotator cuff (shoulder), causing pain and inflammation. The condition is related to and may cause adhesive capsulitis ("frozen shoulder").

De Quervain syndrome, is a tenosynovitis of the sheath or tunnel that surrounds two tendons that control movement of the thumb.

Symptoms associated with tennis elbow include, but are not limited to: radiating pain from the outside of the elbow to the forearm and wrist, pain during extension of wrist, weakness of the forearm, a painful grip while shaking hands or torquing a doorknob, and not being able to hold relatively heavy items in the hand. The pain is similar to the condition known as "golfer's elbow", but the latter occurs at the medial side of the elbow.

Symptoms are pain at the radial side of the wrist, spasms, tenderness, occasional burning sensation in the hand, and swelling over the thumb side of the wrist, and difficulty gripping with the affected side of the hand. The onset is often gradual. Pain is made worse by movement of the thumb and wrist, and may radiate to the thumb or the forearm.

The exact etiology of tendinopathy has not been fully elucidated and different stresses may induce varying responses in different tendons. There are multifactorial theories that could include: tensile overload, tenocyte related collagen synthesis disruption, load-induced ischemia, neural sprouting, thermal damage, and adaptive compressive responses. The intratendinous sliding motion of fascicles and shear force at interfaces of fascicles could be an important mechanical factor for the development of tendinopathy and predispose tendons to rupture. Obesity, or more specifically, adiposity or fatness, has also been linked to an increasing incidence of tendinopathy.

The most commonly accepted cause for this condition however is seen to be an overuse syndrome in combination with intrinsic and extrinsic factors leading to what may be seen as a progressive interference or the failing of the innate healing response. Tendinopathy involves cellular apoptosis, matrix disorganization and neovascularization.

Tendinopathy can be induced in animal models by a surgical injury to the tendon. In both sheep shoulder (infraspinatus) and horse forelimb (superficial digitor flexor) tendons, a mid-tendon transection caused pathology in the entire tendon after four and six weeks respectively.

Quinolone antibiotics are associated with increased risk of tendinitis and tendon rupture. A 2013 review found the incidence of tendon injury among those taking fluoroquinolones to be between 0.08 and 0.2%. Fluoroquinolones most frequently affect large load-bearing tendons in the lower limb, especially the Achilles tendon which ruptures in approximately 30 to 40% of cases.

The most common manifestation of infectious tenosynovitis is in the flexor tendons of the fingers, though infections of other tendon sheaths have been reported as well. The four cardinal signs of infectious flexor tenosynovitis are tenderness to touch along the flexor aspect of the finger, symmetric enlargement of the affected finger, the finger being held in slight flexion at rest, and severe pain with passive extension. Fever may also be present but is uncommon.

Tenosynovitis is the inflammation of the fluid-filled sheath (called the synovium) that surrounds a tendon, typically leading to joint pain, swelling, and stiffness. Tenosynovitis can be either infectious or noninfectious. Common clinical manifestations of noninfectious tenosynovitis include de Quervain tendinopathy and stenosing tenosynovitis (more commonly known as trigger finger)

Children with autosomal dominant MED experience joint pain and fatigue after exercising. Their x-rays show small and irregular ossifications centers, most apparent in the hips and knees. A waddling gait may develop. Flat feet are very common.

The spine is normal but may have a few irregularities, such as scoliosis. There are very small capital femoral epiphyses and hypoplastic, poorly formed acetabular roofs. Knees have metaphyseal widening and irregularity while hands have brachydactyly (short fingers) and proximal metacarpal rounding. By adulthood, people with MED are of short stature or in the low range of normal and have short limbs relative to their trunks. Frequently, movement becomes limited at the major joints, especially at the elbows and hips. However, loose knee and finger joints can occur. Signs of osteoarthritis usually begin in early adulthood.

Children with recessive MED experience joint pain, particularly of the hips and knees, and commonly have deformities of the hands, feet, knees, or vertebral column (like scoliosis). Approximately 50% of affected children have abnormal findings at birth (such as club foot or twisted metatarsals, cleft palate, inward curving fingers due to underdeveloped bones and brachydactyly, or ear swelling caused by injury during birth). Height is in the normal range before puberty. As adults, people with recessive MED are only slightly more diminished in stature, but within the normal range. Lateral knee radiography can show multi-layered patellae.

The congenital absence of the gluteal muscle was described in 1976, as occurring in a brother and sister with absence of gluteal muscles and with spina bifida occulta. It was thought to be caused by an autosomal recessive gene.

Edgar "et al." (2012) reported the case of a 15-year-old white male with congenital absence of the "gluteus maximus" muscles associated with spina bifida occulta, learning disability, optic nerve hypoplasia, scoliosis, and central nervous system hamartomas.

If gluteal muscles were absent the following actions would not be possible. The "gluteus maximus" extends the thigh at the hip in actions like stair climbing, running or walking. It also abducts the thigh, elevates the trunk and also prevents the trunk of a person from moving forward or backward when the rest of the body is in movement. The "gluteal maximus" also aids in stabilizing the femur and the tibia. The "gluteas minimus" and "medius" are also part of the gluteal muscles. If these muscles were missing, the leg would not be able to abduct or medial rotate the thigh. The body would also not be able to shift weight from one side to the other when one foot is on the ground but not another. Considering this a rare congenital disease with other complications, walking would also not be possible in the list of additional symptoms above.

Pathology is insertional tendinopathy of the medius and tendons and enlargement of the associated bursa.

Gluteals remain inactive in a seated position. Movements that require muscles become more difficult; stress is put on the spine.

Fairbank's disease or multiple epiphyseal dysplasia (MED) is a rare genetic disorder (dominant form: 1 in 10,000 births) that affects the growing ends of bones. Long bones normally elongate by expansion of cartilage in the growth plate (epiphyseal plate) near their ends. As it expands outward from the growth plate, the cartilage mineralizes and hardens to become bone (ossification). In MED, this process is defective.