Osteoarthritis is the commonest arthropathy in small cats. This is a slowly progressive, degenerative and often painful joint disease. Secondary osteoarthritis occurs much more often than primary (idiopathic) osteoarthritis.
The possible causes include trauma, inflammation and developmental anomalies as well as metabolic, endocrine, neuropathic, neoplastic, iatrogenic and congenital conditions.
Typical clinical symptoms are pain and immobility of the affected joint or joints.
The typical radiological findings are a joint effusion and cartilage degeneration. Widening of the joint space can be seen initially, and narrowing is visible later. Increased subchondral bone density and mineralisation of intra- and periarticular soft tissue structures are also usual. Due to neovascularisation of the chondrosynovial junction, there is fibrocartilaginous transformation and perichondral ossification as well as osteophyte formation.
The severity of the radiological findings does not always correlate with the severity of the pain.
Development of pain in osteoarthritis / mechanism of action of radiotherapy
The pain of chronic degenerative joint disease is caused by local metabolic disturbances with sustained tissue acidosis (excessive acidity of the tissue) plus irritation of the synovial membrane, joint capsule and joint nerves.
The mechanisms of action underlying the effect when treating osteoarthritis are not fully known. Among other things, there are anti-inflammatory effects at the cellular level, including an effect on synovial lining cells and synovial fluid synthesis. In addition, it appears to affect the pH of the synovial fluid and thus reduce pain perception. Direct effects on the neurovegetative and neuroendocrine system also appear to play a part. Changes in the bone pathology itself cannot be expected.
Our osteoarthritis treatment protocol consists of 3 fractions of 2 Gy each. They can be given within one week or as one fraction per week.
The dose per fraction (2 Gy) and the total dose (6 Gy), as mentioned above, are very low compared with the doses given to treat neoplasms so no side effects are to be expected.
Onset of action
It sometimes takes several weeks before we see an improvement in the lameness and a reduction in pain. About 70 - 80% of cats show sometimes pronounced pain relief.
In cases where the patients are not completely pain-free after the radiotherapy, combinations with a much reduced dose can lead to freedom from pain. If the pain recurs, the radiotherapy can be repeated.
© AniCura, Dr. Julia Buchholz