Joint pathology is the study of diseases and disorders that effect the joints.

In this section we will focus on the following joint pathology:

Osteoarthritis
Rheumatoid arthritis
Seronegative spondyloarthropathies (ankylosing spondylitis, Reiter syndrome, psoriatic arthritis)
Infectious arthritis
Gout
Pseudogout

Joint

The link between two bones is made by joints.

In general, there are three (3) types of joints:

Fibrous
Cartilaginous
Synovial

Cranial sutures are solid fibrous joints that are securely attached to provide structural support.

Synovial joints have a joint gap that permits motion.

For synovial joints, a joint capsule surrounds the hyaline cartilage that makes up the articular surface of adjacent bones.

In order to lubricate synovial joints and promote fluid mobility, the synovium lining of the joint capsule secretes fluid that is high in hyaluronic acid.

Joint. - Not altered. CC BY-SA 3.0
Joint. Types of joints based upon their structure (L to R): Cartilaginous joint, Fibrous joint, and Synovial joint. www.scientificanimations.com - Not altered. CC BY-SA 4.0
Joint. Not altered, Public Domain

Degenerative Joint Disease

Osteoarthritis

Osteoarthritis is due to wear and tear that results in articular cartilage degeneration over time in degenerative joint disease.

This type of arthritis is the most prevalent in the elderly.

Risk factors for osteoarthritis include:

Being 60-years-old or older
Obesity

Osteoarthritis is known as oligoarticular because it only affects a few joints.

Common sites of osteoarthritis include:

Knees
Lower lumbar spine
Hips
Finger joints (proximal (PIP) and distal (DIP) interphalangeal joints)

Common symptoms of osteoarthritis include:

Joint stiffness in the morning
Joint stiffness that becomes worse throughout the day
Joint stiffness that worsens with activity

Pathologic assessment will show absent of disrupted cartilage on the articular surface of the joint.

Eburnation (eroded cartilage) and osteophytes (bony outgrowths) are classically seen in osteoarthritis.

Fragments of cartilage floating in the joint space are called joint mice.

Additionally, osteophyte formation that typically develops in the distal interphalangeal (DIP) (Heberden nodes) and proximal interphalangeal (PIP) (Bouchard nodes) joints of the fingers.

Osteoarthritis. Damaged cartilage from sows. (a) cartilage erosion (b)cartilage ulceration (c)cartilage repair (d)osteophyte (bone spur) formation. Rikke K Kirk, Bente Jørgensen, Henrik E Jensen - Not altered. CC BY 2.0
Osteoarthritis. With physiotherapist Barbora Kinclová about arthrosis. Drahreg. Not altered, CC BY-SA 3.0
Osteoarthritis. X-ray of erosive osteoarthritis of the fingers, also zooming in on two joints with the typical "gull-wing" appearance. Rennett Stowe and Mikael Häggström - Not altered. CC BY 4.0
Osteoarthritis. Histopathology of osteoarthrosis of a knee joint in an elderly female. KGH (talk | contribs). Not altered. CC BY-SA 3.0
Osteoarthritis. Primary osteoarthritis of the left knee. Note the osteophytes, narrowing of the joint space (arrow), and increased subchondral bone density (arrow). James Heilman, MD - Not altered. CC BY-SA 3.0.
Osteoarthritis. MRI of osteoarthritis in the knee, with characteristic narrowing of the joint space. No machine-readable author provided. - Not altered. CC BY-SA 3.0
Osteoarthritis. Severe osteoarthritis and osteopenia of the carpal joint and 1st carpometacarpal joint. James Heilman, MD Not altered. CC BY-SA 3.0
Osteoarthritis. Hip joint with osteoarthritis CFCF - Not altered. CC BY-SA 4.0
Osteoarthritis. Secondary osteoarthritis (due to an old injury with fracture) of the ankle in a patient of 82 years old Jmarchn. Not altered. CC BY-SA 3.0
(A) There is abundant staining of proteoglycans within cartilage with chondrocytes visible within this section of normal cartilage stained with toluidine blue. (B) Early osteoarthritic cartilage showing loss of cartilage extracellular matrix staining, reduction in chondrocytes, and early fibrillation of the articular surface of cartilage; stained with fast green and toluidine blue. (C) Severely damaged osteoarthritic cartilage showing profound loss of proteoglycans staining and fissuring of the cartilage articular surface. The section is stained with toluidine blue. Osteoarthritis samples (B) and (C) were obtained at the time of joint replacement surgery from a patient with osteoarthritis. Future directions for the management of pain in osteoarthritis: Sofat N, Kuttapitiya A - International journal of clinical rheumatology (2014). Not altered. CC.

Rheumatoid Arthritis (RA)

Rheumatoid arthritis (RA) is a chronic, systemic autoimmune condition.

Rheumatoid arthritis (RA) typically affects women above childbearing age.

Rheumatoid arthritis (RA) is linked to HLA-DR4 and is distinguished by joint involvement.

The hallmarks of rheumatoid arthritis (RA) include:

Synovitis
Pannus formation
Inflammatory granulation tissue

Rheumatoid arthritis (RA) may result in joint ankylosis (fusion) and cartilage degradation.

There are several clinical features that can be seen in rheumatoid arthritis (RA) which include:

Morning stiffness that gets better with movement
Symmetric involvement of the proximal interphalangeal (PIP) joints in the fingers
Swan-neck deformity
Wrist or ulnar deviation
Pain in the knees, ankles, and elbows
Distal interphalangeal (DIP) joints are usually spared (unlike osteoarthritis)
Fevers
Weight loss
Malaise
Myalgia
Baker cyst or enlargement of the bursa below the knee
Pleural effusions
Lymphadenopathy
Interstitial lung fibrosis

Radiology of rheumatoid arthritis (RA) classically shows osteopenia, cartilage loss, and a narrowing of the joint space on X-ray.

The F_c component of IgG, a rheumatoid factor, is the target of an IgM autoantibody.

Synovial fluid tests of rheumatoid arthritis (RA) show:

Increased neutrophils
Increased protein
Decreased glucose

Complications of rheumatoid arthritis (RA) include:

Anemia of chronic disease
Secondary amyloidosis

Rheumatoid Arthritis. X-ray of the hand in rheumatoid arthritis. Bernd Brägelmann Braegel. Not altered. CC BY 3.0
Rheumatoid Arthritis. A hand severely affected by rheumatoid arthritis. James Heilman, MD Not altered. CC BY-SA 3.0
Rheumatoid Arthritis. Closeup of bone erosions in rheumatoid arthritis.[59] Haruko Ideguchi, Shigeru Ohno, Hideaki Hattori, Akiko Senuma and Yoshiaki Ishigatsubo. Not altered. CC BY 2.0
Rheumatoid Arthritis. X-ray of the wrist of a woman with rheumatoid arthritis, showing unaffected carpal bones in the left image, and ankylosing fusion of the carpal bones 8 years later in the right image. Mikael Häggström. Not altered. CC0
Rheumatoid Arthritis. X-ray of the wrist of a woman with rheumatoid arthritis, showing unaffected carpal bones in the left image, and ankylosing fusion of the carpal bones 8 years later in the right image. Mikael Häggström - Not altered. CC0
Wright stain images of a patient with rheumatoid arthritis.Notes: (A) Activated macrophage in synovial fluid of rheumatoid arthritis. wright stain, synovial fluid smear from a patient with rheumatoid arthritis 1,000×; (B) and (C) macrophages phagocytizing a small lymphocyte and neutrophil granulocytes. wright stain 1,000× (rheumatoid arthritis).The macrophages in rheumatic diseases. Laria A, Lurati A, Marrazza M, Mazzocchi D, Re KA, Scarpellini M - Journal of inflammation research (2016). Not Altered. CC.

Seronegative Spondyloarthropathies

Lack of rheumatoid factor is one of the characteristics of this group of joint disorders.

HLA-B27 involvement and the axial skeleton are associated.

The sacroiliac joints and spine are affected by ankylosing spondyloarthritis, which develops in young adults, most frequently in men.

Low back pain is one of the symptoms of seronegative spondyloarthropathies.

Eventually, the involvement of vertebral bodies appears, causing the vertebrae to fuse together or form a bamboo spine.

Extra-articular manifestations of ankylosing spondyloarthritis include:

Uveitis
Aortitis leading to aortic regurgitation
Reiter syndrome

Reiter syndrome also includes the triad of:

Conjunctivitis
Urethritis
Arthritis

Reiter syndrome appears in young individuals, mainly men, weeks after an infection with Chlamydia trachomatis.

Psoriatic arthritis is seen in 10% cases of patients with psoriasis.

Psoriatic arthritis typically involves axial and peripheral joints, and the most common afflicted DIP joints are those in the hands and feet, which can result in sausage fingers or toes.

Psoriatic arthritis is associated with scaly rashes.

Seronegative Spondyloarthropathies. Bone scintigraphy made with 99mTc demonstrating the highly enhanced tumor borders and the left elbow affected by psoriatic arthritis. Panagiotis V Kitsoulis, Georgios Paraskevas, Aristidis Vrettakos and Aikaterini Marini; Not altered. CC BY-SA 2.0
Standard radiography of the left sacroiliac joint. (A) No bony erosion could be detected (B) Tomosynthesis (coronal plane) and (C) CT scan (axial plane) examination disclose subtle subchondral erosions of the sacroiliac joints (arrows), whereas bone sclerosis (large arrow) is depicted on standard CT scan. Seronegative spondyloarthropathy imaging: Looking at the past, hitting the future: Lacout A, Carlier R, Marcy PY - The Indian journal of radiology & imaging (2015 Oct-Dec). Not altered. CC.

Infectious Arthritis

A bacterial infection of the joint space that causes inflammation is infectious arthritis.

Neisseria gonorrhoeae in young adults, which is the most frequent cause, is one example of a bacterial cause of infectious arthritis.

Staphylococcus aureus, the second most prevalent cause of infectious arthritis, is a factor that affects older kids and adults.

The knee is the typical affected joint of infectious arthritis, and it typically manifests as a heated joint with restricted range of motion.

Infectious arthritis causes an elevated erythrocyte sedimentation rate (ESR), leukocytosis (a raised white blood cell count), and fever.

Magnification :40 × Stain :haematoxylin and eosin. A Case of Septic Arthritis of Shoulder Presenting as Stiffness of the Shoulder: Journal of Orthopaedic Case Reports. Not altered. CC.
Infectious Arthritis. Septic arthritis of the ankle as seen in a 3 month old Tetsuo Hagino, Masanori Wako, Satoshi Ochiai. Not altered. CC BY 2.5
Infectious Arthritis. Synovial fluid from a knee with septic arthritis James Heilman, MD - Not altered. CC BY-SA 4.0
(H and E, x400): Well-formed epithelioid granulomas with Langhans giant cells and necrosis. Nontuberculous mycobacterial arthritis of the first metatarsophalangeal joint in a young immunocompetent adult: an interesting case report: Vamseedhar A, Padmanabhan AK, Chakkirala NM, Darbur RS - Journal of global infectious diseases (2013). Not altered. CC.

Gout

Gout is due to monosodium urate (MSU) crystal deposition in tissues, particularly the joints, as a result of hyperuricemia.

Gout is connected to uric acid overproduction or decreased uric acid excretion.

Purine metabolism produces uric acid, which the kidney excretes.

The most prevalent kind of gout is primary, however the cause of hyperuricemia is uncertain.

Monosodium urate (MSU) crystals deposit in the joint, triggering an acute inflammatory reaction.

Secondary gout is observed in patients with leukemia and myeloproliferative diseases due to increased cell turnover that causes hyperuricemia.

Lesch-Nyhan syndrome which is a X-linked deficiency of hypoxanthine-guanine phosphoribosyltransferase (HGPRT) presents with mental retardation, self-mutilation, and gout.

Reduced renal excretion of uric acid is a sign of renal insufficiency.

Podagra, an excruciatingly painful great toe arthritis, is the classic manifestation of gout.

Risk factors for gout include:

Alcohol consumption
Cured meat consumption (salami, pepperoni, etc.)

Gout classically has tophi, which are white, chalky, and form along with fibrosis and a giant cell response.

In the soft tissue and joints of people with chronic gout, uric acid crystal can accumulate into aggregates called gouty tophi.

Laboratory results of gout typically show hyperuricemia.

Urate crystals associated with gout can accumulate in the kidney tubules, and may result in renal failure (urate nephropathy).

Histology of gout shows yellow needle-shaped crystals with negative birefringence under polarized light.

Gout treatments include:

Lifestyle modification
Nonsteroidal anti-inflammatory drugs (NSAIDs)
Colchicine
Allopurinol

Gout. Gout presenting as slight redness in the metatarsal–phalangeal joint of the big toe James Heilman, MD - Not altered. CC BY-SA 3.0
Gout. Gout on X-rays of a left foot in the metatarsal-phalangeal joint of the big toe. Note also the soft tissue swelling at the lateral border of the foot. Hellerhoff Not altered. CC BY-SA 3.0
Gout. Gross pathology of a large tophus Mikael Häggström, M.D. - Not altered. CC0
Gout. Gout in the big toe of left foot, compared to the healthy right foot Parkov - Not altered. CC BY-SA 4.0
Gout. Gout complicated by ruptured tophi, the exudate of which tested positive for uric acid crystals James Heilman, MD - Not altered. CC BY-SA 3.0
Gout. Tophii on the toe and ankle Herbert L. Fred, MD and Hendrik A. van Dijk -Not altered. Attribution
Gout. Gouty tophi presenting as nodules on the finger and helix of the ear Herbert L. Fred, MD and Hendrik A. van Dijk -Not altered. Attribution
Gout. Light microscopy of a touch preparation of a gout tophus, showing needle-shaped crystals. Mikael Häggström - Not altered. CC BY-SA 4.0
Gout. Black-and-white photograph of the arms and hands of a 50-year-old man, showing large tophi of sodium urate affecting the elbow, knuckles, and finger joints. Not altered. CC-BY-4.0

Pseudogout

Pseudogout results from calcium pyrophosphate dihydrate (CPPD) deposition.

Clinically, pseudo-gout is similar to gout.

In pseudogout, synovial fluid exhibits rhomboid-shaped crystals with weakly positive birefringence under polarized light.

Pseudogout. Microscopy with polarized light of tissue by a metatarsal joint, showing crystals whereof some (one annotated) have rhomboid shape and weak positive nirefringence, consistent with calcium pyrophosphate dihydrate crystal deposition disease (pseudogout). Mikael Häggström, M.D Not altered. CC0
Pseudogout. Micrograph showing crystal deposition in an intervertebral disc. H&E stain. Nephron - Not altered. CC BY-SA 3.0
Pseudogout. X-ray of a knee with chondrocalcinosis. Taokinesis. Mikael Häggström - Not altered. CC0
Pseudogout. Pseudogout crystals (calcium pyrophosphate dihydrate crystals) Mohamed Elshennawy, M.D. - Not altered. CC BY-SA 4.0
Pathology Slide - Birefringent Calcium PyrophosphateHigh power showing crystals within synovial-chondroid material. The crystals are birefringent on polarization optics, consistent with calcium pyrophosphate. Recurrent Craniocervical Pseudogout: Indications for Surgical Resection, Surveillance Imaging, and Craniocervical Fixation: Manhas A, Kelkar P, Keen J, Rostad S, Delashaw JB - Curēus (2016). Not altered. CC.