Drop Squats vs. Leg Extension/ Curl for Jumper’s Knee

A randomised clinical trial of the efficacy of drop squats or leg extension/leg curl exercises to treat clinically diagnosed jumper’s knee in athletes: pilot study. Cannell LJ, Taunton JE, Clement DB, Smith C, Khan KM. Br J Sports Med. 2001 Feb;35(1):60-4.

Abstract
OBJECTIVES:

To compare the therapeutic effect of two different exercise protocols in athletes with jumper’s knee.
METHODS:

Randomised clinical trial comparing a 12 week programme of either drop squat exercises or leg extension/leg curl exercises. Measurement was performed at baseline and after six and 12 weeks. Primary outcome measures were pain (visual analogue scale 1-10) and return to sport. Secondary outcome measures included quadriceps and hamstring moment of force using a Cybex II isokinetic dynamometer at 30 degrees/second. Differences in pain response between the drop squat and leg extension/curl treatment groups were assessed by 2 (group) x 3 (time) analysis of variance. Two by two contingency tables were used to test differences in rates of return to sport. Analysis of variance (2 (injured versus non-injured leg) x 2 (group) x 3 (time)) was also used to determine differences for secondary outcome measures.
RESULTS:

Over the 12 week intervention, pain diminished by 2.3 points (36%) in the leg extension/curl group and 3.2 points (57%) in the squat group. There was a significant main effect of both exercise protocols on pain (p<0.01) with no interaction effect. Nine of 10 subjects in the drop squat group returned to sporting activity by 12 weeks, but five of those subjects still had low level pain. Six of nine of the leg extension/curl group returned to sporting activity by 12 weeks and four patients had low level pain. There was no significant difference between groups in numbers returning to sporting activity. There were no differences in the change in quadriceps or hamstring muscle moment of force between groups.
CONCLUSIONS:

Progressive drop squats and leg extension/curl exercises can reduce the pain of jumper’s knee in a 12 week period and permit a high proportion of patients to return to sport. Not all patients, however, return to sport by that time.

Diagnosis:  Patellar tendinopathy

Outcome:  VAS. Over 12 weeks pain dropped 2.3 points (36%) in the leg extension/curl group and 3.2 points (57%) in the squat group. 9/10 in the drop squat group returned to sports but 5 still had low level pain. 6/9 of the leg extension/curl group returned to sports 4 of which still had low level pain.

When Assessed:  6 and 12 weeks

Subjects:  7 males and 3 females in the drop squat group, average age 26. 6 males and 3 females in the leg extension/curl group, average age 26.

Protocol:  Squat group did 3 sets of 20 bilateral drop squats once a day 5 days per week for 12 weeks. Starting from a standing position they unlocked their knees and dropped rapidly until thighs were just short of parallel to the ground, starting with body weight and adding resistance when easy, appears they rose back to standing with concentric leg activity so not a pure eccentric program. Leg extension/curl group did 3 sets of 10 reps, once a day 5 days per week, instructed to lift slowly, hold weight 2 seconds at top, with entire rep to take 5 seconds. They started with 5 kg and increased resistance when they could do 3 sets of 10 with that weight.

Other Activity:  “Once the subject’s knee pain was completely absent, he/she began an alternate day running program beginning with 1 km in running athletes and increasing by 1 km every third run…”

Chad’s Comments:  Both groups had improved function and decreased pain. The drop squats were intended to increase eccentric activity but both groups included concentric and eccentric action.

As always, if you have any further questions or need for clarifications, please don’t hesitate to ask. Being aware that some of my blog ideas are contentious and occasionally a bit out of the field of my expertise, I encourage my readers to come forth with any questions/comments that are of interest or concern. Your comments are valued and welcomed.

Chad Reilly is a licensed physical therapist, located in North Phoenix, practicing science based medicine with treatment protocols unique and effective enough to proudly serve patients from Phoenix, Scottsdale, Mesa, Chandler, Tempe, Peoria, and Glendale.

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