I. Radiological Findings

MRI sequences of the patient’s right/left knee joint (based on the visible side in the images, hereafter referred to as the “knee joint”) reveal:

• Significant synovial thickening and joint effusion can be seen within the joint cavity. The synovium shows increased signals on T2-weighted images, indicating local exudation and inflammatory changes.
• A mild degree of subchondral bone destruction or erosion may exist, with abnormal bone signal changes observed in certain areas, and some regions showing bone marrow edema.
• Partial wear of the articular cartilage surface is noted, but no extensive cartilage loss is observed.
• Some degree of surrounding soft tissue edema or exudation is visible, suggesting the spread of inflammation, along with thickened synovium in certain areas.

Overall, these findings are consistent with intra-articular infection or chronic inflammatory joint disease. Further clinical correlation is necessary for differential diagnosis.

II. Potential Diagnoses

1. Tuberculous Arthritis: Considering that Mycobacterium tuberculosis was cultured from the patient’s synovial fluid, with a positive tuberculin skin test, and imaging findings indicating chronic synovial thickening and bone erosion, this presentation aligns with common characteristics of tuberculous arthritis.
2. Other Chronic Infectious Arthritis: For example, suppurative bacterial infection. However, these typically present with acute onset, common bacterial pathogens are usually easily cultured, and the disease course is relatively short; not entirely consistent with this case.
3. Rheumatic Diseases (e.g., Rheumatoid Arthritis): Clinically may show similar joint changes, but immunological indicators (such as RF, anti-CCP antibodies) can differentiate. Moreover, Mycobacterium tuberculosis has already been confirmed in this patient’s joint fluid.
4. Other Rare Synovial or Joint Disorders: Including pigmented villonodular synovitis, synovial chondromatosis, etc. However, these diseases typically lack clear signs of infection or definitive evidence of tuberculosis.

III. Most Likely Final Diagnosis

Combining the patient’s clinical presentation (joint swelling and pain, synovial thickening), imaging features (chronic synovial proliferation with bone changes), and laboratory/pathogen findings (isolation of Mycobacterium tuberculosis in joint fluid, positive tuberculin skin test, etc.), the most likely diagnosis is Tuberculous Arthritis.

For further confirmation, a synovial biopsy and observation of therapeutic response to anti-tuberculosis medications may be considered.

IV. Treatment Plan and Rehabilitation

1. Pharmacological Treatment:
   • First-line anti-tuberculosis therapy typically includes isoniazid, rifampin, pyrazinamide, and ethambutol in the standard four-drug regimen. The treatment course is usually prolonged (≥6 months), with regular follow-up of liver function and other potential adverse reactions.
   • During the acute inflammatory phase or when joint pain is severe, a short-term use of non-steroidal anti-inflammatory drugs (NSAIDs) can help relieve pain and inflammation. However, NSAIDs should be used in conjunction with anti-tuberculosis medications, with careful monitoring for adverse effects.
2. Surgical Treatment (depending on the situation):
   • If there is a significant lesion within the joint, marked joint destruction, or other complications, surgical debridement, synovectomy, or, if necessary, joint reconstructive surgery may be considered.
   • Postoperatively, patients should continue anti-tuberculosis therapy and undergo rehabilitation exercises.
3. Rehabilitation and Exercise Prescription:
   • During the acute inflammatory phase, it is recommended to rest in bed or reduce weight-bearing, using braces or other external supports to alleviate load on the joint.
   • After the acute phase, gradually begin joint activity training:
     • Frequency: 3-5 times per week, adjusted according to pain and joint response.
     • Intensity: Start with passive range of motion exercises, progress to active exercises, and then introduce low resistance training. Increase resistance based on pain tolerance and range of motion.
     • Time: 10-20 minutes per session, in segments as needed, avoiding excessive load at once.
     • Type: Range-of-motion exercises, gentle flexion and extension, closed-chain/open-chain exercises (e.g., seated knee extensions, straight leg raises). Avoid high-impact activities.
     • Progression: As inflammation subsides and joint function improves, gradually introduce light muscle-strengthening exercises, such as partial squats or elastic band workouts, to enhance lower limb strength.
     • Volume: Begin with a very low volume and gradually increase to a moderate volume, avoiding excessive loads that could increase joint pain or cause reinjury.
   • Throughout the rehabilitation process, exercise should be individualized based on pain, swelling, and overall health status. Coordination with physical therapists or rehabilitation physicians is recommended when necessary.

V. Disclaimer

This report is based on available clinical and radiological information for analysis and is intended for reference only. It is not a substitute for in-person hospital visits or the clinical judgment of professional healthcare providers. If you have any questions or if there are any changes in condition, please seek medical attention or professional healthcare services promptly.