Classification of Loose Bodies

Loose bodies can be of 3 types depending on its etiology:

• loose bodies due to Synovial Chondromatosis
• loose bodies due to Osteochondral fracture
• loose bodies due to joint surface disintegration


Three different types of cartilage can be identified in the nidus of a loose body–
a) articular,
b) osteophytic, &
c) lobular.

Three mechanisms for the generation of loose bodies in cases of degenerative arthritis or avascular necrosis are:
1. fragmentation of the joint surface
2. fractured osteophytes
3. osteochondral nodule proliferation in the pararticular soft tissues

For more details please read this article:
The classification of loose bodies in human joints
by Milgram JW.




Synovial Chondromatosis

-A proliferative disease of the synovium resulting from cartlaginous/osteocartilaginous metaplasia in the synovium of joints, bursae or tendon sheath.
-multiple cartilaginous nodules develop & grow in the synovium of a joint
-results in multiple intra-articular loose bodies.

-30-50 years
–♂:♀ = 2:1
-knee, the most common site



Pathology

• SITE
  -Knee, elbow, ankle, hip & shoulder (in that order of frequency)
  -usually monoarticular but may affect both knee
• Macroscopic features
  -hundreds of spheroid nodules protruding into the joint cavity
  -formation of rice-bodies/joint mice
  –Snow storm appearance on arthroscopy
• Microscopic features
  -hyaline cartilage formation at stratum synoviale at the synovial reflection
  -Chondroid masses appearance at the tips of synovial villi
  -surrounding cells altered to resemble chondroblast
  -Cartilage mass grows to form spheroid body with villous process as its pedicle.
  -spheroid body detaches & falls free into joint space
  -Chondroblast continue to proliferate & form spheroid cartilage
  -Chondroblast metaplsia into Osteoblast forming nidus of bone surrounded by cartilage
  -Joint-distended with uniform glistening white bodies
  -repeated trauma to articular surface causing multiple erosions & subsequently osteoarthritis



Clinical features

• Symptoms:
  -usually mild & slow progression of the symptoms
  -Pain, dull aching type
  -Swelling
  -Stiffness
  -Transient locking episodes
• Signs(Physical Examination):
  -generalized joint tenderness
  -warmth, erythema
  -decreased ROM (range of motion)
  -thickened synovial membrane
  -marked audible & palpable crepitus
  -loose bodies may be felt.



Imaging evaluation

1. Radiograph/Plain x-ray:
   -AP & Lateral views of the joint——— variable finding(s)
   -stippled calcification
   -multiple loose bodies (if calcified), number is always more than what can be seen in the X-ray.
2. MRI:
   -best to see initial chondromatous(cartilage) nodules (Lobular appearance)
   -when calcified, signal drop-out consistent with calcification
3. Double contrast/air Arthrography: can be used for all cartilaginous lesion(s).



Histology

-individual hyaline cartilage nodules (various stages of calcification & ossification)
-Chondrocyte showing mild atypia, binucleate cells & occasional mitoses


Differential diagnosis

-Rheumatoid arthritis: fragments of articular cartilage detach & augment into synovium or goes free in the joint.
-Osteoarthritis: many osteophytes may detach into the joint.

Treatment

1. Conservative/Non-operative:
   -Obsevation if movement of the joint is not affected.
   -Analgesics
2. Operative/Surgical:
   –Synovectomy (open vs arthroscopic) plus loose bodies resection, indicated in cases with severe symptoms affecting the joint movement.
   -early intervention prevents the degenerative joint changes.
   –Total synovectomy with excision of all communicating bursae
   -In case of knee joint, the damaged menisci may need removal
   -If the degenerative changes have already developed, the patient should warn about residual symptoms.



Prognosis

-chances of Recurrence is there
-Malignant transformation (very rare)