yogabook / pathology / knee joint effusion

Definition

A knee joint effusion is an acute or chronic accumulation of joint fluid, blood (haemarthrosis) or pus (pyarthrosis) in the joint capsule. The term „water in the knee“ is also used imprecisely in everyday language. The synovial membrane is irritated by a pathological event and produces more synovial fluid. The synovial fluid becomes less viscous than normal and can become cloudy due to cell abrasion. If blood vessels are damaged, haemarthrosis occurs, if bacteria are involved, pyarthrosis occurs. A distinction must be made between 4 cases:

1. Serous case: The effusion fluid in meniscus damage and cartilage damage is clear with a beer-brown colour, in other more severe degenerative diseases and rheumatic events it is cloudy with a lot of proteins and cell debris. In the case of slight joint contusions and fresh patellar dislocations, the serous fluid may also be mixed with blood.
2. Purulent case (empyema): A purulent effusion is an orthopaedic emergency. It is usually caused by bacterial arthritis and is divided into primary (pathogens enter the joint from outside, traumatically or iatrogenically) and secondary (haematogenous entry into the joint from distant primary foci such as teeth, otitis media, meningitis, tuberculosis). The purulent effusion must be treated immediately, as there is a risk of joint damage and septicaemia.
3. Haemarthrosis: capsular injuries, ligament injuries or bone injuries such as fractures and avulsions or blood clotting disorders cause a bloody effusion. If the bone marrow cavity is opened, its fat leaks out and floats on the effusion.
4. Fibrinous effusion: the effusion fluid contains fibrin and is usually caused by more serious inflammatory or traumatic events.

Knee joint effusions in younger people are often caused by overuse, in older people they are usually the result of degenerative or rheumatic events. Acute traumatic effusions usually occur in younger, athletically active people.

Cause

1. iatrogenic: due to interventions in the knee joint or infections in the context of invasive interventions
2. Injuries or overloading of structures of the knee joint (ligaments, menisci)
3. Activated arthrosis
4. Arthritis in Lyme disease, Morbus Reiter or Psoriatic arthritis
5. Patellar luxation or subluxation
6. Plica syndrome
7. autoimmunological, then usually originating from the synovial membrane
8. Rheumatic diseases, e.g. RA, Morbus Bechterew, SLE
9. Haemophilia
10. Gout
11. Pseudogout (chondrocalcinosis): Deposition of Ca crystals
12. Carcinomatosis

Predisposing

Diagnosis

1. Sono, MRT
2. Tests and signs: dancing patella (from approx. 50 ml effusion), brush test
3. Pathogen determination after puncture if necessary

Symptoms

1. All signs of inflammation, swelling is visible and palpable, altered joint contour
2. Restriction of mobility due to pressure (especially inhibition of flexion)
3. Pain on movement, often felt retropatellar

Complication

1. in purulent cases: sepsis, panarthritis with capsular shrinkage and consecutive stiffening of the joint and destruction of the articular cartilage
2. the increased intra-arterial pressure can overstretch the joint capsule and lead to joint instability
3. In the serous case: secondary Baker’s cyst

Therapy

1. In non-traumatic cases: treatment of the underlying disease
2. Reduction of strain, elevation
3. Cooling
4. If the cause is trauma: rest from sport
5. Therapy of the underlying disease
6. After movement restrictions due to sprains, gradual mobilisation and resumption of exercise
7. NSAIDs if necessary, also as an ointment
8. Puncture if necessary, but not multiple times (risk of infection)
9. Intra-articular cortisone injection if necessary in purulent cases
10. In purulent cases: repeated antiobiotic irrigation of the knee joint until negative pathogen detection
11. Acute traumatic effusions usually heal without consequences with adequate treatment
12. PT, stretching training, strength training
13. Gait analysis or analysis of athletic movement sequences if necessary

DD