Differential Diagnosis of the Painful

Brian D. Busconi and Brett D. Owens

Hip and pelvis injuries encompass a wide spectrum of pathology resulting from repetitive microtraumatic stresses or acute traumatic forces. Fortunately, the majority of these injuries heal without permanent sequelae; however, accurate recognition and prompt appropriate treatment are required to minimize complications. Approximately 2.5% of all sports-related injuries are located in the hip and pelvic area. Epidemiolog-ical surveys suggest that injuries to the hip and pelvis account for approximately 5% of all injuries sustained by adult athletes. Runners and soccer players may also be somewhat more prone to injuries of the hip and groin. Soft tissue injuries include muscular, tendinous, or ligamentous inflammation, contusion or strain and rupture or avulsion. Skeletal injuries involve the epiphysis, physis, apophysis, metaphysis, or dia-physis. Skeletal pathology includes complete or incomplete fractures, stress reactions, dislocations, avulsion, infection, inflammation, and acquired pathologic conditions.

Hip pain typically regarded as nontraumatic (eg inflammatory conditions such as rheumatoid arthritis, juvenile arthritis and ankylosing spondylitis, infections, benign or malignant tumors, and metabolic bone disease) may be induced by physical activity and consequently present to the health care team. Nerve entrapment syndromes of the ilioinguinal, genitofemoral, and lateral cutaneous nerve of the thigh can manifest as pain and/or paresthesia in their respective territories. It is essential that systemic illness manifesting as hip pain is not overlooked and should be considered when the severity or course of the injury is not in keeping with the presumed diagnosis.

The differential diagnosis of hip pain must, in addition, include structures distant to the joint and periarticular tissues. The importance of referred pain from the lumbar spine, abdominal and pelvic viscera, genitourinary problems, sacroiliac problems, sporting hernias, osteitis pubis, and other pelvic conditions should also be considered. Similarly, pain from the knee and thigh may be referred proximally to the hip and vice versa.

Persistent hip pain can also originate from intra-articular pathology such as synovitis, loose bodies, avascular necrosis (AVN), acetabular labral tears, or infection. Pain is usually the chief complaint of patients with hip problems. These patients may present with pain over the anterior or lateral aspect of the hip, in the groin, or more medially in the region of the adductors, corresponding to the obturator nerve distribution. (Figure 2.1) Pain may radiate distally to the knee. Pain referred to the hip may be secondary to spinal problems, which must be considered in the differential diagnosis of patients with "hip" pain.

Most patients with hip pain have increased pain with activity. Measurements of joint forces reveal that peak forces at the hip can exceed four times body weight when going from a slow to fast walking speed. Jogging can increase this force up to six times body weight. This increased force is primarily generated by the muscles about the hip. (Figure 2.2) Those who complain of pain at rest usually have some inflammatory component to their disease. An infectious or neoplastic process may be present. Many patients will report increased pain as they begin activity. Pain is increased when the patient loads a joint that has been at rest. As the joint accommodates the new level of activity, pain subsides.

Patients with chronic progressive disease, such as os-teoarthritis, report progressively severe pain. They often report prior problems (e.g. injury or childhood disease including developmental dysplasia, avascular necrosis or slipped capitofemoral epiphysis). Adults with avascular necrosis may describe the onset of pain months or years after cortisone use. Excessive alcohol ingestion may be a contributing cause of avascular necrosis.

Patients will complain of stiffness, which may be worst in the morning or may be a more constant problem affecting many activities of daily living. To obtain an accurate analysis, patients should be questioned to determine their impairment in walking, dressing, stair climbing, and foot hygiene.

Neurovascular Supply The Pelvis
Figure 2.1. Drawing of the nerve supply to the pelvis and thigh.

Anterior inferior

Anterior inferior

Anterior Soft Tissues Neck
Figure 2.2. Drawing of the rectus tendon anatomy.

Contusions

Among the most frequently experienced hip and pelvic injuries sustained by competitive, skeletally immature athletes are soft tissue contusions.1-3 Contusions usually result from direct blows to a specific soft tissue area, usually overlying a bony prominence. Contusions are most common in contact sports, especially football, but are also seen in volleyball, hockey, and basketball. In contact sports, the blow is usually caused by contact with another athlete. In noncontact sports, athletes usually sustain blows from contact with equipment (gymnastics), contact with high velocity projectiles (lacrosse ball), or contact with the playing surface.

Contusions are often found over the bony prominences of the pelvis, which include the iliac crest (hip pointer), greater trochanter, ischial tuberosity, and pubic rami. Because of the varied anatomy of the pelvis, contusions can be superficial, especially when they overlie a relatively subcutaneous bone or lie deep within a large muscle mass. It is important to determine the possible presence and extent of muscular hemorrhage, because an increase in muscular hemorrhage often results in more severe symptomatology and thus, a longer time before returning to sport.

Pain and hemorrhage over the iliac crest has been referred to as a hip point.4,5 Injuries here include contusions, avulsion of the iliac apophysis, periostitis, and/or avulsion of the muscles that insert onto the iliac crest. On physical examination, the patient will have superficial or muscular hemorrhage which is painful on palpation. It is important to note by touch a defect which would indicate an avulsion injury. Patients have difficulty with rotation and side bending of the trunk. Anterior-posterior and oblique x-rays of the pelvis will rule out an avulsion fracture, periostitis, or acute fracture of the iliac wing.

Strains

Soft tissue injuries to the periarticular structures surrounding the hip and pelvis are the most common injuries seen. In general, the great majority of soft tissue injuries about the hip and pelvis are musculotendinous strains. The type of injury sustained is highly dependent upon: the skeletal age of the athlete, physical condition, and the biomechanical forces involved in both the sport and the nature of the trauma. The degree of injury can range from repetitive mi-croinjury associated with each performance to a more significant single macroinjury caused by an abnormal biome-chanical force. A certain degree of microtrauma occurs with every major exertional performance; that is immediately manifested by swelling, sensitivity, and a recovery interval. If additional moderate or severe micro- or macroinjury occurs, there may not be a normal healing response; this may lead to more significant changes in tissue structure and have a negative effect on future athletic performance. This section on soft tissue injuries will follow a correlative anatomic and functional approach to acute and chronic performance-related injuries to the hip and pelvis, as well as provide treatment guidelines.

A strain is an injury to a musculotendinous structure caused by an indirectly applied force. The most common mechanism of injury is a result of eccentric contraction or stretching of an activated muscle.7,8 The site of injury is influenced by the rate of loading, the mechanism of injury, and local anatomic factors. Low rates of loading will result in a failure at the tendon-bone junction by bone avulsion or disruption at its insertion. High rates of loading result in intratendinous or my-otendinous junction injuries.

These injuries can be graded on a three-level clinical grading system.9 Grade 1 injuries involve a simple stretching of soft tissue fibers. Grade 2 strains involve partial tearing of the musculotendinous unit. Grade 3 injuries, which are unusual, are secondary to extremely violent forces causing complete disruptions. Diagnosis and treatment of these injuries will be described with each anatomic area. It is important to note that an injury which causes partial or complete soft tissue disruptions in adults can cause an apophyseal avulsion injury in children.

Athletic Pubalgia

The term "athletic pubalgia" refers to a chronic inguinal or pubic area pain in athletes, which is noted on exertion. The pattern of symptoms in these patients, operative findings, and the results of studies all suggest that the lower abdominal/ inguinal pain is not usually due to an occult hernia. When this does occur, the occult hernia is usually found on the side opposite that of the principal symptoms.

The rectus tendon insertion on the pubis seems to be the primary site of pathology. Most patients describe a hyperextension injury in association with hyperabduction of the thigh. The location of the pain suggests that the injury involves both the rectus abdominis and adductor longus muscles. Other tendinous insertion sites on the pubic bone may also be involved.

The athletes have lower abdominal pain with exertion. A minority of patients have purely adductor-related pain, which is disabling. Most patients remember a distinct injury during exertion. Usually, the abdominal pain involves the inguinal canal near the insertion of the rectus muscle on the pubis. This pain causes a majority of patients to stop competing in sports.

MRI findings in athletic pubalgia are often nonspecific. On the other hand, 12% of patients have MRI findings which clearly indicate a problem at the rectus insertion site. The relatively small incidence of a specific diagnosis by imaging studies suggests that the problem may be an attenuation of the muscle or tendon due to repeated microtrauma. The MRI finding of adductor longus inflammation is consistent with athletic pubalgia.

Generally, the acute management of groin pain suspected to be athletic pubalgia is conservative, and includes rest, ice, compression, anti-inflammatory medications, and massage.10 When the process continues over several months and the athlete cannot return to previously expected activity because of pain, an operation should be considered. Surgical treatment of athletic pubalgia requires a broad surgical reattachment at the inferolateral edge of the rectus muscle with its fascial investments to the pubis and adjacent anterior ligaments. We also perform an anterior and lateral release of the epimysium of the adductor fascia in order to expand this compartment. The epimysium is the layer of connective tissue that encloses the entire muscle. This kind of fascial release is often very successful in relieving the adductor symptoms in athletic pubalgia.11

Piriformis Syndrome

In 1928, Yeoman first described a syndrome involving compression of the sciatic nerve by the piriformis muscle. The nerve compression occurs as it exits deep to the piriformis muscle.12 Patients complain of pain and symptoms in the sciatic nerve distribution. A history of past acute trauma to the buttock is often present. Patients will have difficulty sitting or participating in activities, such as ice skating, which involve hip flexion and internal rotation.13 On physical examination, tenderness is present over the piriformis tendon in the gluteal area. Pain is elicited by forced internal rotation on an extended thigh, or Pace's sign, (ie pain and weakness on resisted abduction and external rotation of the thigh). Rectal or vaginal examination may produce pain in the piriformis area. An MRI can be helpful to demonstrate sciatic nerve inflammation in the area of the piriformis tendon.

Hamstring Syndrome

In 1988, Puranen described an entity called Hamstring syndrome, which was very common in track athletes.14,15 Athletes have severe pain in and around the ischial tuberosity, which radiates down the posterior aspect of the thigh to the popliteal area. Any activity which stretches the hamstring can create this radiating pain. Sprinting, hurdling, and even sitting for long periods will cause pain. Physical examination elicits exquisite tenderness at the ischial tuberosity and, at times, reproduction of sciatic pain with percussion of the nerve at the ischial tuberosity. Resisted leg extension will reproduce the pain. The sciatic nerve is thought to be entrapped between the semitendinosus and the biceps femoris by a fibrous band which constricts the two muscles.

Inflammatory Disorders

Inflammation of the sacroiliac joint can occur with a variety of the spondyloarthropathies. Reiter's syndrome, psoriatic arthritis, ankylosing spondylitis, and inflammatory bowel disease commonly occur with sacroiliitis. In other patients, there may be sacroiliac pain without other signs of spondyloarthropathy. Pain may be from true synovitis of this joint, or from inflammation of the overlying muscles or ligaments.

Pain occurs over the sacroiliac joint region, with referred pain into the lower buttock and thigh. Pain over the greater trochanter and groin pain may also be present. Tenderness is present over the sacroiliac joint and in the region of the posterior superior iliac spine. Patrick's test may elicit pain in the involved joint. With the patient lying on one side, strong compression of the pelvis may cause pain. Hyperextension of the hip may also produce pain. X-rays frequently show no significant change. In the case of spondyloarthropathy, however, there may be irregularity or osteopenia of the subchondral bone, leading to "blurring" of the joint space. These changes are most commonly seen in the lower (synovial) part of the joint. Patchy areas of lucency and sclerosis may develop. With further progression, marked narrowing of the joint space occurs, and ankylosis can be present.

When sacroiliitis is a manifestation of an underlying spondyloarthropathy, treatment is dictated by the underlying inflammatory disease. In isolated cases of sacroiliac syndrome, symptomatic relief can be achieved by rest, application of local heat or ice, and use of nonsteriodal anti-inflammatory medication. A sacroiliac belt may also be helpful.

Inflammatory involvement of the hip joint may also be caused by rheumatoid arthritis.

Snapping Hip Syndrome

Snapping hip syndrome is a collection of extra-articular and intra-articular pathologies which can be not only painful and disabling to the athlete, but also confusing for the diagnosti cian.16-18 Extra-articular snapping of the hip joint can be caused by the following: The iliopsoas tendon as it passes over the iliopectineal eminence or the lesser trochanter of the femur; the iliofemoral ligaments over the femoral head; the long head of the biceps femoris over the ischial tuberosity; or finally and most commonly the iliotibial band over the greater trochanter of the femur. It can be very difficult for the practitioner to distinguish these entities from more disconcerting intraarticular lesions, such as tears of the anterior labrum, syn-ovitis, or loose bodies, which can also create a snapping or clicking sensation in the hip. However, as CT, MRI, and hip arthroscopy become more refined we are better able to differentiate these entities.

Another cause of snapping hip syndrome is irritation of the greater trochanter by the iliotibial band. The iliotibial band is a large flat tendinous structure that originates on the anterior superior portion of the iliac crest, crosses over the greater trochanter of the femur, and inserts onto the lateral condyle of the tibia. Iliotibial band syndrome is seen in athletes who undergo repetitive knee flexion, such as runners and cyclists.17,19 Athletes have pain over the greater trochanter of the femur, the lateral thigh, or pain radiating down to the knee. Patients often complain that their "hip feels like it's dislocating" or "it seems to pop in and out of joint." If it is severe enough, the snapping sensation occurs during normal ambulation. Once this area becomes inflamed, running or rising from a seated position may cause it to hurt continuously.

Bursitis

Bursitis about the hip is a common condition secondary to inflammation of one of the three major bursae about the hip: the trochanteric bursa, the iliopsoas bursa, and the ischiog-luteal bursa. These bursae facilitate the gliding of muscu-lotendinous or ligamentous structures. Bursitis may be secondary to direct injury or overuse of the adjacent muscu-lotendinous structures, or to degenerative changes in these structures. Because bursae are lined by true synovial tissue, bursitis also can occur with systemic disease, causing synovitis.

The trochanteric bursa is a large bursa that lies between the greater trochanter and the overlying junction of the gluteus maximus and tensor fascia lata, as these merge to form the fascia lata and iliotibial tract.

Ischiogluteal bursitis is inflammation of the bursa between the ischial tuberosity and the overlying gluteus max-

imus. This inflammation usually is associated with injury or with occupations requiring long periods of sitting. The patient complains of pain over the ischial tuberosity that is aggravated by sitting, and the pain may radiate into the posterior thigh. Tenderness is present overlying the ischial bursa, but swelling is rarely noted. X-rays are usually noncontributory.

The iliopsoas bursa is located between the iliopsoas muscle and the pelvis proximally, and between the hip capsule and the psoas tendon distally. Inflammation of the iliopsoas bursa will usually cause groin pain. Communication between the hip joint and psoas bursa is common.

Arthritis

Osteoarthritis is one of the most common diseases affecting the adult hip. This condition is often secondary to an underlying abnormality of the hip, such as developmental dyspla-sia, Legg-Calve-Perthes disease, or slipped capital femoral epiphysis. (Figure 2.3) In some cases, however, there is no identifiable cause, and in these situations the osteoarthritis is considered primary or idiopathic. As a result of these changes, motion in the hip becomes progressively restricted, first by painful synovitis and muscle spasm, then by secondary soft tissue contracture. In more advanced stages of the disease, there is loss of joint congruity, osteophyte formation, and mechanical block to motion superimposed on the soft tissue contracture.

Pain in osteoarthritis can be caused by this synovitis or by muscle spasm, capsular contracture, and pain fibers in bone and reparative granulation tissue. The patient presents with pain, which may be felt in the groin, buttock, anterior thigh, or knee. Pain is usually worse with weight-bearing, although there may be pain at rest. Initially, the pain may be intermittent, but with time it becomes more frequent, lasts longer, and becomes progressively severe. The patient may limp, which may be an antalgic limp or an "abductor sway."

Motion is restricted and may be demonstrable as a flexion contracture. Abduction and internal rotation are usually more restricted than adduction and external rotation. The leg shortens with advanced disease. X-ray of the hip demonstrates varying changes, including narrowing of the joint space, subchondral bone irregularity with cyst and osteo-phyte formation, sclerosis of the subchondral trabecular bone, and lateral or superolateral subluxation of the femoral head.

Septic Arthritis

Adult patients rarely develop septic arthritis of the hip. Those patients who develop septic arthritis are frequently immunocompromised (eg patients with diabetes or renal failure, or those taking corticosteroids or chemotherapeutic agents). The intravenous drug abuser is also at increased risk. A healthy patient who develops septic arthritis presents acutely ill with high fever, exquisite pain, and decreased motion. An im-munocompromised patient, however, may present without high fever and may not appear acutely ill. Range of motion may not be as painful.

Tuberculosis can occur in the hip joint as in any other synovial tissue. Pain, limited motion, subcutaneous abscess, or a draining sinus may be part of the presentation. In the advanced stages of this disease, x-ray changes are significant and demonstrate bone and joint destruction.

A patient suspected of having infectious arthritis of the hip must undergo joint aspiration and should be referred immediately to the orthopedist.

Avascular Necrosis

Avascular necrosis of the femoral head is well recognized in association with fractures of the femoral neck and disloca tions of the femoral head in both adults and children. Fracture of the femoral neck is associated with a 15-30% risk of avascular necrosis. Dislocation of the hip is associated with a 10-15% risk of avascular necrosis. The primary cause of avascular necrosis of the femoral head after direct hip trauma is an interruption of the arterial supply to the femoral head secondary to the injury. Evidence suggests that avascular necrosis also may be the result of a short-duration shower of fat emboli that can occur after significant trauma. Avascular necrosis of the femoral head without recognizable injury is not well understood and may be multifactorial. In patients with sickle cell disease, avascular necrosis is thought to be associated with vascular thrombosis. Avascular necrosis has been commonly associated with alcoholism and long-term steroid use.

Avascular necrosis after brief exposure to corticosteroids occurs uncommonly and is not well understood, but the potential risk is certainly great enough to justify caution when prescribing systemic corticosteroids for prolonged periods. There is no known risk of avascular necrosis after single or repeated trigger-point or intra-articular injections. Avascular necrosis has also been noted in gout, Gaucher's disease, caisson disease, and in patients with altered hemostasis. In several large series of patients with avascular necrosis, the idio-pathic category remains the largest group, followed by those with alcohol-related or corticosteroid-induced disease. Ve

Decompression Illness

Figure 2.

Figure 2.

:.3. Plain nous compression has been implicated as a cause for avascular necrosis, especially in decompression sickness, pregnancy, or thrombophlebitis. Embolic causes typically are centered on fat emboli as the inciting event. Intraosseous fat embolism not only obstructs blood flow directly, but is also hypothesized to mediate vascular occlusion through an intermediary pathway of localized intravascular coagulation.

The pathologic change associated with the early phase of this disease is a segmental necrosis of the femoral head. The overlying articular cartilage is unaffected. With time, there is reparative tissue ingrowth with resorption of necrotic bone, accompanied by formation of new bone on necrotic trabecu-lae. With resorption, the area of segmental necrosis weakens, and a subchondral fracture can occur. Patients often have a marked increase in pain when this happens. Avascular necrosis is clinically categorized in stages based on the x-ray appearance of the hip.20 The condition is frequently bilateral in nontraumatic cases.

Labral Tears

A torn acetabular labrum has been identified as a cause for hip discomfort in athletics. Its clinical features include a painful click in the inguinal area, catching, or giving way symptoms. In general, athletes will remember an antecedent traumatic event, which often involves sports that require forceful hip extension and rotation such as karate. On physical examination, the painful click can be reproduced by a McCarthy sign (with the opposite hip fully flexed, the affected hip is extended, first in external rotation then in internal rotation). Radiographic measures have been unreliable and have low diagnostic yields.

It is this group of patients with refractory hip pain, reproducible physical findings, and equivocal or negative radiographic studies in whom hip arthroscopy has been successful in diagnosis and treatment. Excellent results have been reported with arthroscopic debridement of the lesion. Return to sports has occurred in our series 6-8 weeks after debridement. Labral tears will be covered in further detail in the chapter on labral pathology.

Fractures and Dislocations

Trauma may result in actual fracture, dislocation, or both. These conditions must always be in the differential diagnosis; however, they will be covered in detail in the chapter on trauma.

Stress fractures of the femur and the pelvis are not common, but often are a source of great confusion in diagnosis. These injuries should be considered in athletes who do a great deal of chronic repetitive motion. They are often seen in track and field athletes, long distance runners, and army recruits. A stress fracture is generally defined as repetitive stress below the failure levels of bone in a time period inadequate to allow for bony remodeling.21-26

Femoral stress fractures are not as common as stress fractures involving the pelvis but, if not identified and treated appropriately, can lead to fracture displacement or AVN of the femoral head.24,27,28 Athletes will present with pain in the groin area, which is persistent and is associated with a decreased range of motion in the affected hip joint. On physical examination, the patient will have a decrease in hip range of motion, especially with flexion and internal rotation. The groin will be painful to touch, and at times percussion of the greater trochanter will elicit pain.

Initial plain radiographs of the hip may be negative for 2-4 weeks following the onset of pain.23,27,29 A technetium 99 bone scan is helpful to confirm the diagnosis of a stress fracture. Recently, magnetic resonance imaging (MRI) has been increasingly used.

Two types of femoral neck stress fractures have been described: transcervical (distraction) and compression.25,30 The first type of stress fracture is a superior transverse fracture involving the superior portion of the femoral neck. It is a distraction injury and fortunately is uncommon in children. It is most commonly seen in an anterior-posterior view of the hip. Displacement is the major complication associated with the treatment of this fracture. Internal fixation is the recommended treatment for a type 1 fracture.27,28

If displacement does occur, it should be treated as an acute transcervical fracture of the proximal femur. The second type of fracture is a compression stress fracture, which is more common in children and rarely displaces.21,28 These fractures are seen on the inferior medial aspect of the femoral neck and are frequently treated with nonweight-bearing status until there is radiographic evidence of callous and healing.

Pelvic stress fractures are also secondary to repetitive microtrauma, often occurring at the junction of the ischium and the inferior pubic ramus. They are very common in female runners between the ages of 19 and 48. The etiology has been postulated as being secondary to tensile stresses created by muscle contractions in the pelvis with the hip in extension.31,32

On clinical examination, the athlete often has pain in and around the inguinal area. The gait will be antalgic. Hip range of motion is usually pain-free and full. Noakes describes a positive standing sign in which the patient develops discom fort in the groin while standing unsupported on the leg with the corresponding pelvic injury.32

Radiographs, as with femoral stress fractures, may not be positive until 2-3 weeks after injury. A bone scan may be performed early to make the diagnosis.

Pediatric conditions such as slipped capital femoral epiphysis, Legg-Calve-Perthes, septic arthritis, and transient syn-ovitis are covered in detail in the chapter on pediatrics.

Tumors

Hip or pelvic pain which persists for longer than expected following an apparently minor injury, or following no known antecedent trauma, must be evaluated for the possibility of a pathologic lesion.

The chief complaint of children with a pathologic lesion to the hip and pelvis is pain in the groin. The quality, location, and nature of the pain varies with the type of pathologic lesion involved and therefore this must be determined. Although most pediatric musculoskeletal tumors do not have associated systemic symptoms, possible symptoms include fever, chills, nausea, vomiting, or decreased appetite, and it is important to determine the presence or absence of these. A thorough physical examination of the pelvis and hip should be performed to ascertain the possible presence of masses, muscular atrophy, or neurovascular changes.

Radiographic evaluation of the affected area is essential. Anterior-posterior and lateral radiographs of the hip and pelvis are performed, and in most cases will be diagnostic. Further studies can include technetium 99 (99Tc) bone scan, CT scan, and/or MRI.

Osteoid osteoma is a benign bone tumor of adolescents and young adults, most frequently affecting the hip and pelvis. It may therefore present as a hip pain syndrome in young athletes. Investigations are geared towards identifying the pathognomonic bony nidus. Plain radiographs may be normal, but linear tomograms, isotope bone scanning, and CT were valuable diagnostic aids. Return to sport was on average 4 months following a limited excisional biopsy via an anterior approach without the need for bone grafting, internal fixation, or cast immobilization postoperatively. The natural history suggests that spontaneous resolution and healing may occur after a prolonged period of time (2-3 years), so conservative management should be considered in surgically complex cases.

Common pathologic lesions to the hip and pelvis include benign lesions (unicameral bone cyst, osteoid osteoma, osteochondroma, or fibrous dysplasia), malignant neoplasm (Ewing's sarcoma and osteogenic sarcoma), and systemic en-docrinopathies (hypothyroidism and renal osteodystrophy). Management of these pathologic lesions should be undertaken in an experienced facility where appropriate diagnostic staging, therapeutic agents, and/or surgical intervention can be employed.

References

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Arthritis Joint Pain

Arthritis Joint Pain

Arthritis is a general term which is commonly associated with a number of painful conditions affecting the joints and bones. The term arthritis literally translates to joint inflammation.

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