Increasing knowledge about the function of the meniscus and arthroscopy have made meniscus surgery more conservative. Arthroscopy was developed during the 70's and enabled the surgeon to select the most appropriate and tissue conserving therapy for a meniscus lesion. Arthroscopic meniscectomy and meniscus repair were introduced as new techniques for treatment of meniscus lesions.

This thesis comprises five long term follow-up studies of arthroscopic meniscectomy and open meniscus repair and one short term follow-up study of arthroscopic meniscectomy.

The long term follow-up studies include 152 patients, 113 with meniscectomy and 39 with meniscus repair, with stable knees, age less than 44 years and without preexisting gonarthrosis. All patients had a diagnostic at1hroscopy at the index operation and were evaluated clinically and radiographically 13-14 years after surgery.

At follow-up the frequency of radiographic changes was high but in general the radiographic changes were of a low grade. Only seven patients, 4 of 86 (5%) after partial meniscectomy and 3 of 27. (11%) after total meniscectomy fulfilled the criteria for gonarthrosis (minimal joint space less than 3 mm on radiographs and symptoms). More radiographic changes were found after total meniscectomy than after partial meniscectomy, meniscus repair or than in an un-injured control group. A similar rate of radiographic changes was seen when meniscus repair was compared to matched patients with partial and total meniscectomy. Knee function was in general good at follow-up and did not differ between patients with total meniscectomy and partial meniscectomy but patients with meniscus repair had a somewhat better knee function than a group of patients with partial and total meniscectomy. Cartilage fibril1ation present at meniscectomy did not influence the frequency of radiographic changes, knee function or activity at follow-up but older patients had more radiographic changes after meniscectomy than younger patients. The activity level decreased in a similar fashion over time after total meniscectomy, partial meniscectomy, meniscus repair and in un-injured subjects indicating that factors other than the knee injury and meniscus operation determines the decline in activity.

Thus, irrespective of meniscus treatment (arthroscopic partial/total meniscectomy and meniscus repair), in a 13-14 year perspective, the grade of radiographic changes in the knee joint were relatively low with no influence on activity and little influence on knee function.

In the short term follow-up study original data from patients with arthroscopic meniscectomy in the early 80' s when the technique was new was compared to similar data from patients operated today, when the technique is in routine use. The operation time was shorter and the frequency of subtotal meniscectomy was less today. In contrast to the early 80's the procedure is entirely out-patient. However, recovery and in particular return to sports were delayed today in comparison to previously.

A less supervised rehabilitation is suggested to be the main cause to the delayed recovery and a generosity with supervised rehabilitation after arthroscopic meniscectomy is advisable.